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  • Rat  (826)
  • evolution  (694)
  • Evolution  (686)
  • growth  (678)
  • Inversion
  • Springer  (2,916)
  • 3
  • Wiley
  • 1
    Publication Date: 2024-04-16
    Description: Color polymorphism is a classic study system for evolutionary genetics. One of the most color-polymorphic animal taxa is mollusks, but the investigation of the genetic basis of color determination is often hindered by their life history and the limited avail-ability of genetic resources. Here, we report on the discovery of shell color polymor-phism in a much-used model species, the great pond snail Lymnaea stagnalis. While their shell is usually beige, some individuals from a Greek population show a distinct red shell color, which we nicknamed Ginger. Moreover, we found that the inheritance fits simple, single-locus Mendelian inheritance with dominance of the Ginger allele. We also compared crucial life-history traits between Ginger and wild-type individuals, and found no differences between morphs. We conclude that the relative simplicity of this polymorphism will provide new opportunities for a deeper understanding of the genetic basis of shell color polymorphism and its evolutionary origin.
    Keywords: evolution ; genetics ; life history ; Mendelian inheritance ; simultaneous hermaphrodites
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 2
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    Springer Nature | Springer
    Publication Date: 2024-04-05
    Description: This open access book offers the first comprehensive account of the pan-genome concept and its manifold implications. The realization that the genetic repertoire of a biological species always encompasses more than the genome of each individual is one of the earliest examples of big data in biology that opened biology to the unbounded. The study of genetic variation observed within a species challenges existing views and has profound consequences for our understanding of the fundamental mechanisms underpinning bacterial biology and evolution. The underlying rationale extends well beyond the initial prokaryotic focus to all kingdoms of life and evolves into similar concepts for metagenomes, phenomes and epigenomes. The book’s respective chapters address a range of topics, from the serendipitous emergence of the pan-genome concept and its impacts on the fields of microbiology, vaccinology and antimicrobial resistance, to the study of microbial communities, bioinformatic applications and mathematical models that tie in with complex systems and economic theory. Given its scope, the book will appeal to a broad readership interested in population dynamics, evolutionary biology and genomics.
    Keywords: Microbial Genetics and Genomics ; Evolutionary Biology ; Genetics and Population Dynamics ; Microbial Ecology ; Human Genetics ; Genetics and Genomics ; Comparative genomics ; Metagenomics ; Microbial Population Analysis ; Pangenome Profile ; Supra-Genome Analysis ; Adaptive Evolution ; Computational Tools ; Bioinformatic Genomics ; Core Dispensable Genome ; Selection, Recombination, Composition ; Acquired Resistance ; Bacterial Species Concept ; Genomic Diversity ; Bacterial Ecology, Microevolution ; Open Access ; Pan-metagenomics ; Pan-microbiomics ; Pan-epigenome ; Gene Transfer ; Pan-phenomes ; Microbiology (non-medical) ; Genetics (non-medical) ; Evolution ; Applied mathematics ; Ecological science, the Biosphere ; Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSG Microbiology (non-medical) ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; thema EDItEUR::P Mathematics and Science::PB Mathematics::PBW Applied mathematics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFN Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAK Genetics (non-medical)
    Language: English
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  • 3
    Publication Date: 2024-01-12
    Description: We present a phylogenetic analysis of spiders using a dataset of 932 spider species, representing 115 families (only the family Synaphridae is unrepresented), 700 known genera, and additional representatives of 26 unidentified or undescribed genera. Eleven genera of the orders Amblypygi, Palpigradi, Schizomida and Uropygi are included as outgroups. The dataset includes six markers from the mitochondrial (12S, 16S, COI) and nuclear (histone H3, 18S, 28S) genomes, and was analysed by multiple methods, including constrained analyses using a highly supported backbone tree from transcriptomic data. We recover most of the higher-level structure of the spider tree with good support, including Mesothelae, Opisthothelae, Mygalomorphae and Araneomorphae. Several of our analyses recover Hypochilidae and Filistatidae as sister groups, as suggested by previous transcriptomic analyses. The Synspermiata are robustly supported, and the families Trogloraptoridae and Caponiidae are found as sister to the Dysderoidea. Our results support the Lost Tracheae clade, including Pholcidae, Tetrablemmidae, Diguetidae, Plectreuridae and the family Pacullidae (restored status) separate from Tetrablemmidae. The Scytodoidea include Ochyroceratidae along with Sicariidae, Scytodidae, Drymusidae and Periegopidae; our results are inconclusive about the separation of these last two families. We did not recover monophyletic Austrochiloidea and Leptonetidae, but our data suggest that both groups are more closely related to the Cylindrical Gland Spigot clade rather than to Synspermiata. Palpimanoidea is not recovered by our analyses, but also not strongly contradicted. We find support for Entelegynae and Oecobioidea (Oecobiidae plus Hersiliidae), and ambiguous placement of cribellate orb-weavers, compatible with their non-monophyly. Nicodamoidea (Nicodamidae plus Megadictynidae) and Araneoidea composition and relationships are consistent with recent analyses. We did not obtain resolution for the titanoecoids (Titanoecidae and Phyxelididae), but the Retrolateral Tibial Apophysis clade is well supported. Penestomidae, and probably Homalonychidae, are part of Zodarioidea, although the latter family was set apart by recent transcriptomic analyses. Our data support a large group that we call the marronoid clade (including the families Amaurobiidae, Desidae, Dictynidae, Hahniidae, Stiphidiidae, Agelenidae and Toxopidae). The circumscription of most marronoid families is redefined here. Amaurobiidae include the Amaurobiinae and provisionally Macrobuninae. We transfer Malenellinae (Malenella, from Anyphaenidae), Chummidae (Chumma) (new syn.) and Tasmarubriinae (Tasmarubrius, Tasmabrochus and Teeatta, from Amphinectidae) to Macrobuninae. Cybaeidae are redefined to include Calymmaria, Cryphoeca, Ethobuella and Willisius (transferred from Hahniidae), and Blabomma and Yorima (transferred from Dictynidae). Cycloctenidae are redefined to include Orepukia (transferred from Agelenidae) and Pakeha and Paravoca (transferred from Amaurobiidae). Desidae are redefined to include five subfamilies: Amphinectinae, with Amphinecta, Mamoea, Maniho, Paramamoea and Rangitata (transferred from Amphinectidae); Ischaleinae, with Bakala and Manjala (transferred from Amaurobiidae) and Ischalea (transferred from Stiphidiidae); Metaltellinae, with Austmusia, Buyina, Calacadia, Cunnawarra, Jalkaraburra, Keera, Magua, Metaltella, Penaoola and Quemusia; Porteriinae (new rank), with Baiami, Cambridgea, Corasoides and Nanocambridgea (transferred from Stiphidiidae); and Desinae, with Desis, and provisionally Poaka (transferred from Amaurobiidae) and Barahna (transferred from Stiphidiidae). Argyroneta is transferred from Cybaeidae to Dictynidae. Cicurina is transferred from Dictynidae to Hahniidae. The genera Neoramia (from Agelenidae) and Aorangia, Marplesia and Neolana (from Amphinectidae) are transferred to Stiphidiidae. The family Toxopidae (restored status) includes two subfamilies: Myroinae, with Gasparia, Gohia, Hulua, Neomyro, Myro, Ommatauxesis and Otagoa (transferred from Desidae); and Toxopinae, with Midgee and Jamara, formerly Midgeeinae, new syn. (transferred from Amaurobiidae) and Hapona, Laestrygones, Lamina, Toxops and Toxopsoides (transferred from Desidae). We obtain a monophyletic Oval Calamistrum clade and Dionycha; Sparassidae, however, are not dionychans, but probably the sister group of those two clades. The composition of the Oval Calamistrum clade is confirmed (including Zoropsidae, Udubidae, Ctenidae, Oxyopidae, Senoculidae, Pisauridae, Trechaleidae, Lycosidae, Psechridae and Thomisidae), affirming previous findings on the uncertain relationships of the \xe2\x80\x9cctenids\xe2\x80\x9d Ancylometes and Cupiennius, although a core group of Ctenidae are well supported. Our data were ambiguous as to the monophyly of Oxyopidae. In Dionycha, we found a first split of core Prodidomidae, excluding the Australian Molycriinae, which fall distantly from core prodidomids, among gnaphosoids. The rest of the dionychans form two main groups, Dionycha part A and part B. The former includes much of the Oblique Median Tapetum clade (Trochanteriidae, Gnaphosidae, Gallieniellidae, Phrurolithidae, Trachelidae, Gnaphosidae, Ammoxenidae, Lamponidae and the Molycriinae), and also Anyphaenidae and Clubionidae. Orthobula is transferred from Phrurolithidae to Trachelidae. Our data did not allow for complete resolution for the gnaphosoid families. Dionycha part B includes the families Salticidae, Eutichuridae, Miturgidae, Philodromidae, Viridasiidae, Selenopidae, Corinnidae and Xenoctenidae (new fam., including Xenoctenus, Paravulsor and Odo, transferred from Miturgidae, as well as Incasoctenus from Ctenidae). We confirm the inclusion of Zora (formerly Zoridae) within Miturgidae.
    Keywords: Ecology ; Evolution ; Behavior and Systematics
    Repository Name: National Museum of Natural History, Netherlands
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  • 4
    Publication Date: 2017-04-04
    Description: We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian basin. The tectonic evolution of the Tyrrhenian basin is dominated by a Tortonian - Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly-magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.
    Description: Published
    Description: 251-266
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: 3.4. Geomagnetismo
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: JCR Journal
    Description: reserved
    Keywords: Geomagnetism ; Tectonics ; Geodynamics ; Inversion ; Oceanic crust ; Volcanic structure ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    In:  Computers and Geosciences, Münster, 3, vol. 28, no. 45, pp. 309-326, pp. L11609, (ISBN 0-471-26610-8)
    Publication Date: 2002
    Keywords: Inversion ; Data analysis / ~ processing ; Non-linear effects ; Discrimination ; C&G
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  • 6
    Electronic Resource
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    Journal of ornithology 141 (2000), S. 263-274 
    ISSN: 1439-0361
    Keywords: Systematics ; evolution ; anagenesis ; genealogy ; reference system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Verglichen mit anderen Tiergruppen, scheint die artliche Bestandsaufnahme der rezenten Vögel nahezu abgeschlossen zu sein. Doch ist das System der Vögel weiterhin umstritten und mit vielen Neuerungen konfrontiert. Die Gründe dafür liegen hauptsächlich in neuen, vor allem molekularbiologischen Methoden und in den unerwartet reichen Fossilfunden der jüngsten Zeit. Als Beispiele werden Altgaumenvögel, Kranichvögel, Ibisse, Flamingos, Mausvögel, Hopfe und Sperlingsvögel kurz behandelt. Die hier erzielten Fortschritte lassen die Befürchtung Stresemanns, die Großsystematik der Vögel sei mit den vorhandenen Methoden phylogenetisch nicht interpretierbar, zunächst als unbergründet erscheinen. Doch erwachsen einer solchen Interpretation andere Hindernisse, deren Bedeutung bisher zu wenig beachtet wurde, nämlich Parallelentwicklungen, die viel verbreiteter sind als gemeinhin angenommen. Ihre Häufigkeit lässt sich sogar mit evolutionsbiologischen Argumenten begründen. Es ist deshalb nicht zu erwarten, dass die Diskussionen um das „richtige“ System bald verstummen. Um dennoch die Eindeutigkeit der Information in nicht-systematischen Veröffentlichungen zu wahren, wird empfohlen ein etabliertes Referenzsystem auf Zeit zu wählen.
    Notes: Summary Unlike in most animal classes the inventory of extant species of the class Aves seems to be almost complete. Nevertheless avian systematics is challenged by many novelties and seems far from being settled. This is caused mainly by the application of novel methods of molecular analysis to phylogenetic problems and by the unexpectedly rich fossil record collected within the last 10–20 years. Examples from the Palaeognathae, Gruiformes, Threskiornithidae, Phoenicopteridae, Coliiformes, Upupiformes and Passeriformes are briefly treated. The progress in the field seems to disprove Stresemann's pessimistic view that the phylogeny of higher categories (orders) cannot be reconstructed by the available methods. However, phylogenetic interpretations are impeded by obstacles not considered by Stresemann and highly underestimated in most cases, namely by multiple independent developments leading to identical features. Frequent parallel developments are to be expected for theoretical evolutionary reasons. The diagnosis of such homoplasies can be extremely difficult or even impossible. Therefore we cannot expect the discussion about the “best” system of birds to end in the near future. Considering this dynamic situation in systematics, it is recommended to maintain unambiguousness of information in not strictly systematic publications by refering to a well established system as a temporally limited reference.
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  • 7
    ISSN: 1570-7458
    Keywords: butterfly ; Formicidae ; food ; growth ; mutualism ; myrmecophily ; parasitism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Caterpillars of the lycaenid butterfly Maculinea rebeli Hirschke (Lepidoptera: Lycaenidae) live for 11–23 months as social parasites in Myrmica (Hymenoptera: Formicidae) red ant nests, a trait that is believed to have evolved from mutualistic myrmecophilous ancestry. Although Maculinea rebeli caterpillars harm Myrmica larvae, they simultaneously produce copious secretions which the adult worker ants imbibe, perhaps representing a vestige of the ancestral mutualism. We report the results of laboratory experiments designed to test alternative hypotheses: (i) Maculinea rebeli caterpillars provide a beneficial source of sugar in return for being tended by Myrmicaworkers; (ii) Maculinea rebeli harms its host by stressing the workers by competing for available sugar. Comparisons were made of Myrmica worker fitness after 90–450 days under all possible combinations of three experimental treatments: ± M. rebeli caterpillars, ± sucrose and ± ant brood. Caterpillars always reduced the survival of both ant workers and their larvae, even when sugar was not provided, suggesting that M. rebeli is wholly parasitic on all stages in its host colony. The results also confirmed the importance of sucrose in the diet of Myrmica, and showed that M. rebeli caterpillars which eat ant brood to supplement their normal trophallactic feeding by workers develop more quickly - but have the same survival and pupal weights – as caterpillars that are fed solely by worker ants.
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  • 8
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    Acta biotheoretica 48 (2000), S. 137-147 
    ISSN: 1572-8358
    Keywords: Sex ; sexual selection ; mate selection ; evolution ; ploidy ; assortative mating ; recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using computer simulations I studied the simultaneous effect of variable environments, mutation rates, ploidy, number of loci subject to evolution and random and assortative mating on various reproductive systems. The simulations showed that mutants for sex and recombination are evolutionarily stable, displacing alleles for monosexuality in diploid populations mating assortatively under variable selection pressure. Assortative mating reduced excessive allelic variance induced by recombination and sex, especially among diploids. Results suggest a novel adaptive value for sex and recombination. They show that the adaptive value of diploidy and that of the segregation of sexes is different to that of sex and recombination. The results suggest that the emergence of sex had to be preceded by the emergence of diploid monosexual organisms and provide an explanation for the emergence and maintenance of sex among diploids and for the scarcity of sex among haploid organisms.
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  • 9
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    Entomologia experimentalis et applicata 97 (2000), S. 237-249 
    ISSN: 1570-7458
    Keywords: herbivores ; predators ; parasitoids ; mutualism ; induced defence ; behaviour ; ecology ; evolution ; sensory physiology ; plant fitness ; pathogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Herbivorous and carnivorous arthropods use plant volatiles when foraging for food. In response to herbivory, plants emit a blend that may be quantitatively and qualitatively different from the blend emitted when intact. This induced volatile blend alters the interactions of the plant with its environment. We review recent developments regarding the induction mechanism as well as the ecological consequences in a multitrophic and evolutionary context. It has been well established that carnivores (predators and parasitoids) are attracted by the volatiles induced by their herbivorous victims. This concerns an active plant response. In the case of attraction of predators, this is likely to result in a fitness benefit to the plant, because through consumption a predator removes the herbivores from the plant. However, the benefit to the plant is less clear when parasitoids are attracted, because parasitisation does usually not result in an instantaneous or in a complete termination of consumption by the herbivore. Recently, empirical evidence has been obtained that shows that the plant's response can increase plant fitness, in terms of seed production, due to a reduced consumption rate of parasitized herbivores. However, apart from a benefit from attracting carnivores, the induced volatiles can have a serious cost because there is an increasing number of studies that show that herbivores can be attracted. However, this does not necessarily result in settlement of the herbivores on the emitting plant. The presence of cues from herbivores and/or carnivores that indicate that the plant is a competitor- and/or enemy-dense space, may lead to an avoidance response. Thus, the benefit of emission of induced volatiles is likely to depend on the prevailing faunal composition. Whether plants can adjust their response and influence the emission of the induced volatiles, taking the prevalent environmental conditions into account, is an interesting question that needs to be addressed. The induced volatiles may also affect interactions of the emitting plant with its neighbours, e.g., through altered competitive ability or by the neighbour exploiting the emitted information. Major questions to be addressed in this research field comprise mechanistic aspects, such as the identification of the minimally effective blend of volatiles that explains the attraction of carnivores to herbivore-infested plants, and evolutionary aspects such as the fitness consequences of induced volatiles. The elucidation of mechanistic aspects is important for addressing ecological and evolutionary questions. For instance, an important tool to address ecological and evolutionary aspects would be to have plant pairs that differ in only a single trait. Such plants are likely to become available in the near future as a result of mechanistic studies on signal-transduction pathways and an increased interest in molecular genetics.
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  • 10
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    Entomologia experimentalis et applicata 95 (2000), S. 141-149 
    ISSN: 1570-7458
    Keywords: ecology ; reproductive success ; fecundity ; intraspecific competition ; evolution ; pest outbreaks ; pest control ; chemical control ; economic threshold ; oilseed rape ; turnip rape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Populations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.
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  • 11
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    Journal of insect behavior 13 (2000), S. 71-86 
    ISSN: 1572-8889
    Keywords: copulatory courtship ; behavioral interactions ; songs ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract D. birchii and D. serrata, two endemic Australian Drosophila species, have a copulatory courtship. The males of these species begin to court the female after mounting her and often go on with the courtship after the copulation is over. In the present paper we have described behavioral interactions between the male and the female and analyzed acoustic signals produced by the flies during courtship. Species differences were more pronounced in female than in male behavior. Variation within the species was obvious in the relative proportions of time the flies spent in different behaviors. Even though courtship took place nearly solely during copulation, some remains of precopulatory courtship were observed in both species. It is suggested that copulatory courtship exhibited by D. birchii and D. serrata flies is a derived rather than a primitive character.
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  • 12
    ISSN: 1572-879X
    Keywords: aluminum oxide ; hydroxyl groups ; rhodium ; growth ; scanning tunneling microscopy ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to investigate how the presence of surface hydroxyl groups on oxide surfaces affects the interaction with the supported metal, we have modified a well-ordered alumina film on NiAl(110) by Al deposition and subsequent exposure to water. This procedure yields a hydroxylated alumina surface as revealed by infrared and high-resolution electron energy loss spectroscopy. By means of scanning tunneling microscopy, we have studied the growth of rhodium on the modified film at 300 K. Clear differences in the particle distribution and density are observed in comparison to the clean substrate. While, in the latter case, decoration of domain boundaries as typical defects of the oxide film governs the growth mode, a more isotropic island distribution and a drastically increased particle density is found on the hydroxylated surface. From infrared data, it can be deduced that the growth is connected with the consumption of the hydroxyl groups due to the interaction between the metal deposit and the hydroxylated areas. This finding is in line with photoemission results published earlier.
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  • 13
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    Geometriae dedicata 83 (2000), S. 31-37 
    ISSN: 1572-9168
    Keywords: Vollständiges Viereck ; Kegelschnittbüschel ; Konjugiertheitsabbildung ; Inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The conjugacy mapping rel. to a complete quadrangle in a Pappian projective plane of characteristic ≠2 is constructed by using a bijection of the line set onto the bundle of conics through the diagonal points of the quadrangle. The inversion with center O of the inversion circle going through the point P in the Euclidean plane proves to be the product of the reflection at OP and the affine restriction of the conjugacy mapping rel. to the quadrangle having P as one of its vertices and O together with the circular points at infinity as diagonal points.
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  • 14
    ISSN: 1572-9028
    Keywords: rutile supported V2O5–WO3 catalyst ; evolution ; NO reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper concerns the relation between surface structure of crystalline vanadia-like active species on vanadia–tungsta catalyst and their activity in the selective reduction of NO by ammonia to nitrogen. The investigations were performed for Ti–Sn-rutile-supported isopropoxy-derived catalyst. The SCR activity and surface species structure were determined for the freshly prepared catalyst, for the catalyst previously used in NO reduction by ammonia (320 ppm NO, 335 ppm NH3 and 2.35 vol% O2) at 573 K as well as for the catalyst previously annealed at 573 K in helium stream containing 2.35 vol% O2. The crystalline islands, exposing main V2O5 surface, with some tungsten atoms substituted for V-ones, were found, with XPS and FT Raman spectroscopy, to be present at the surface of the freshly prepared catalyst. A profound evolution of the active species during the catalyst use at 573 K was observed. Dissociative water adsorption on V5+OW6+ sites is discussed as mainly responsible for the catalyst activity at 473 K and that on both V5+OW6+ and V4+OW6+ sites as determining the activity at 523 K.
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  • 15
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    Foundations of science 5 (2000), S. 429-456 
    ISSN: 1572-8471
    Keywords: awareness ; reflexive awareness and consciousness ; evolution ; experience and pattern matching ; symbolic language
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General
    Notes: Abstract An evolutionary point of view is proposed to make more appropriate distinctions between experience, awareness and consciousness. Experience can be defined as a characteristic linked closely to specific pattern matching, a characteristic already apparent at the molecular level at least. Awareness can be regarded as the special experience of one or more central, final modules in the animal neuronal brain. Awareness is what experience is to animals. Finally, consciousness could be defined as reflexive awareness. The ability for reflexive awareness is distinctly different from animal and human awareness and depends upon the availability of a separate frame of reference, as provided by symbolic language. As such, words have made reflexive awareness – a specific and infrequent form of awareness – possible. Conciousness might be defined as the experience evoked by considering, i.e. thinking about experiences themselves. If there is a hard problem of explaining consciousness, than this actually must be considered as the hard problem already met when trying to explain basic experience, since its nature remains elusive.
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  • 16
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    Journal for general philosophy of science 31 (2000), S. 57-73 
    ISSN: 1572-8587
    Keywords: complex systems ; evolution ; nonlinearity ; pre-determination ; self-organization ; soft management ; structure-attractors ; synergetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Philosophy , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract The philosophical consequences of synergetics, the interdisciplinary theory of evolution and self-organization of complex systems, are being drawn in the paper. The idea of discreteness of evolutionary paths is in the focus of attention. Although the future is open, and there are many alternative evolutionary paths for complex systems, not any arbitrary (either conceivable or desirable) evolutionary path is feasible in a given system. There are discrete spectra of possible evolutionary paths which are determined exclusively by inner properties of the corresponding systems. Synergetics allows us to reveal general laws of self-organization and, therefore, certain limits of arbitrariness of nature in choosing possible paths of evolution as well as in constructing of a complex evolutionary whole. A comparative analysis between the modern synergetic notions and a few ideas of the Western philosophy (F. Nietzsche, N. Hartmann, M. Heidegger) and of the Eastern teachings (Taoism, Buddhism) is made.
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  • 17
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    International journal of value-based management 13 (2000), S. 297-308 
    ISSN: 1572-8528
    Keywords: morality ; moral systems ; behavior ; evolution ; adaptation ; natural selection ; altruism ; reciprocal altruism ; fitness ; reciprocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The ethical and moral behavior of Homo sapiens is no longer the exclusive domain of religion and philosophy because we recognize that such behavior affects the reproductive success of individuals within the species. We are a social species and therefore our survival is influenced by our capacity for cooperation and our willingness to take risks for kin. Emotions, some of which are found in other species, help to mediate our altruistic behavior. The reproductive benefits of helping kin, especially offspring, are readily seen. Helping non-kin can be beneficial if individuals can differentiate between ‘reciprocators’ and ‘non-reciprocators’ and direct altruistic behavior toward reciprocators. Also, if third parties are favorably impressed by observing altruistic behavior, the rewards need not come from the recipient of the altruistic behavior.
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  • 18
    ISSN: 1432-1211
    Keywords: Key words Antigen presentation ; Autoimmune disease ; Evolution ; MHC ; Self peptides
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    Topics: Biology , Medicine
    Notes: Abstract  Comparison of peptides eluted from human class I and class II major histocompatibility complex (MHC) molecules and the proteins from which they are derived (source proteins) revealed that class I MHC bind peptides derived from proteins that are highly conserved, hydrophilic, and universally expressed, while the peptides themselves are hydrophobic and even more conserved than their source proteins. In contrast, source proteins for class II-bound peptides were not significantly more conserved than a random sample of proteins. Class II-bound peptides were generally more conserved than their source proteins but were significantly less conserved than class I-bound peptides. The characteristics of class I-bound peptides can probably be explained by the selectivity of processing and transport of peptides for binding by class I, while the relative lack of selectivity of peptide binding for class II may explain the high incidence of autoimmune diseases associated with alleles of these molecules.
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  • 19
    ISSN: 1432-1211
    Keywords: Key words iNOS ; Fish ; Parasite ; Evolution ; Transcription
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    Topics: Biology , Medicine
    Notes: Abstract  Using an oligonucleotide primer based on a partial goldfish inducible nitric oxide synthase (iNOS) sequence, a complete carp iNOS cDNA was isolated from an activated carp phagocyte cDNA library. Nucleotide and predicted amino acid sequence analysis indicate that carp iNOS encodes a 1127-amino acid protein with 57% sequence identity to human iNOS. Like mammalian NOSs, carp iNOS protein contains putative binding sites for heme, tetrahydrobiopterin, calmodulin, flavine mononucleotide, flavine adenine dinucleotide, and NADPH. Phylogenetic analysis, using neighbor joining, showed that the carp iNOS protein clustered together with the other vertebrate iNOS proteins. Inducibility of carp iNOS was confirmed by reverse transcription-polymerase chain reaction after stimulation of carp phagocytes with lipopolysaccharide or the protozoan blood flagellate Trypanoplasma borreli. These stimulators produced high amounts of nitric oxide that were toxic for T. borreli in vitro. The nuclear transciption factor NF-κB was shown to play a role in the induction of iNOS transcription.
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  • 20
    ISSN: 1432-1211
    Keywords: Key words HLA ; Patr class I molecules ; Evolution ; Polymorphism ; AIDS
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    Topics: Biology , Medicine
    Notes: Abstract  Human immunodefiency virus (HIV) poses a major threat to humankind. And though, like humans, chimpanzees are susceptible to HIV infection, they are considered to be resistant to the development of the acquired immune deficiency syndrome (AIDS). Little is known about major histocompatibility complex (MHC) class I diversity in chimpanzee populations and, moreover, whether qualitative aspects of Patr class I molecules may control resistance to AIDS. To address these questions, we assayed MHC class I diversity in a West African chimpanzee population and in some animals from other subspecies of chimpanzee. Application of different techniques allowed the detection of 17 full-length Patr-A, 19 Patr-B, and 10 Patr-C alleles. All Patr-A alleles cluster only into the HLA-A1/A3/A11 family, which supports the idea that chimpanzees have experienced a reduction in their repertoire of A locus alleles. The Patr-B alleles do not cluster in the same lineages as their human equivalents, due to frequent exchange of polymorphic sequence motifs. Furthermore, polymorphic motifs may have been exchanged between Patr-A and Patr-B loci, resulting in convergence. With regard to evolutionary stability, the Patr-C locus is more similar to the Patr-A locus than it is to the Patr-B locus. Despite the relatively low number of animals analyzed, humans and chimpanzees were ascertained as sharing similar degrees of diversity at the contact residues constituting the B and F pockets in the peptide-binding side of MHC class I molecules. Our results indicate that within a small sample of a West African chimpanzee population, a high degree of Patr class I diversity is encountered. This is in agreement with the fact that chimpanzees display more mitochondrial DNA variation than humans. In addition, population analyses demonstrated that particular Patr-B molecules, with the capacity to bind conserved HIV-1 epitopes, are characterized by high gene frequencies. These findings have important implications for evaluating immune responses in HIV vaccine studies and, more importantly, may help in understanding the relative resistance of chimpanzees to AIDS.
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  • 21
    ISSN: 1432-1211
    Keywords: Key words HLA genes ; IgV genes ; Evolution ; Gene conversion ; Sheep ileal Peyer's patch
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    Topics: Biology , Medicine
    Notes: Abstract  Polymorphic sequence variation in the peptide-binding domains of MHC class I molecules appears to have been driven largely by the constructive action of natural selection on the specificity of the peptide-binding groove. Similar features are displayed by the variable domains of immunoglobulins generated in the sheep ileal Peyer's patch, but in this case there is evidence that the action of a targeted hypermutator acting on a selected substrate rather than antigen-driven selection is responsible for the pattern of variation in the system. Such a hypermutator acting in the germ line would not only mimic the action of natural selection but also, by convergent mutation, generate similar patterns of variation in unrelated alleles that could be interpreted as evidence for short-tract gene conversion. We analyzed human class I MHC alleles in the light of these data, but failed to find evidence of the action of a similar hypermutator. A search for other mutationally driven patterns of variation also failed, even in hypervariable residues from parsimonious phylogenies. Single-nucleotide variation at these residues is also frequent in recent allelic variants, but the data are as consistent with short-tract gene conversion as with base mutation. We conclude that the patterns of allelic variation in MHC molecules are not driven by mutational pressure, but rather by conventional mutational processes, accompanied by short-tract gene conversion and intense natural selection.
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  • 22
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    Immunogenetics 51 (2000), S. 587-590 
    ISSN: 1432-1211
    Keywords: Key words J chain ; Immunoglobulin ; Amphibian ; Evolution ; Comparative immunology
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  • 23
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    Immunogenetics 51 (2000), S. 606-609 
    ISSN: 1432-1211
    Keywords: Key words MHC ; Evolution ; Primate ; Callithrix ; Callicebus
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  • 24
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    Mycorrhiza 10 (2000), S. 145-149 
    ISSN: 1432-1890
    Keywords: Keywords Arbuscular mycorrhiza ; Pteridophyte ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The percentage of arbuscular mycorrhizal pteridophytes among 256 pteridophyte species distributed in Yunnan (southwest China) was found to be lower than that in angiosperms. In the pteridophytes, the occurrence of arbuscular mycorrhizas was low in sporophytes of fern-allies and leptosporangiates, whereas in the eusporangiates it was relatively high. From the standpoint of mycotrophism, the evolutionary trend in the Filicineae may be from constantly mycorrhizal to facultative mycorrhizal and finally to nonmycorrhizal plants.
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  • 25
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    Journal of comparative physiology 186 (2000), S. 105-118 
    ISSN: 1432-1351
    Keywords: Key words Stomatogastric nervous system ; Penaeus ; Motor pattern ; Neural network ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Motor patterns of the cardiac sac, the gastric and the pyloric network in the stomatogastric nervous system of the shrimp Penaeus japonicus, the most primitive decapod species, were studied. Single neurons can switch from the gastric or the pyloric pattern to the cardiac sac pattern. Some of the pyloric neurons fire with the gastric pattern. All of the gastric neurons fire with the pyloric pattern, unlike those in reptantians. Proctolin activates and modulates the cardiac sac and the pyloric rhythm, and promotes reconfiguration of the networks. Neurons of the three networks have so many interconnections that they construct a multifunctional neural network like those in Cancer. This network may function in different configurations under the appropriate conditions. Several modes of interactions between the networks found in different reptantian species can apply to the penaeidean shrimp. Such interactions are general features of the stomatogastric nervous system in decapods. Phylogenetic differences among the decapod infraorders are seen in the number and orientation of muscles and the innervation pattern of muscles. The multifunctional networks have existed in the most primitive decapod species, and types of configurations of the networks would have evolved to produce a wide range of motor patterns as the foregut structure has become complex.
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  • 26
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    Small business economics 14 (2000), S. 195-210 
    ISSN: 1573-0913
    Keywords: growth ; manufacturing ; performance ; product innovation ; small firms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The paper considers the relative performance [along a number of parameters] of a sample of 228 small manufacturing firms categorised by level of innovation. Whilst innovators appear no more likely to have experienced some form of sales or employment growth, they are significantly more likely to have grown more. In other words, the innovators' growth rate distributions are highly negatively skewed. With regards to export intensities, profitability and productivity levels, the findings are less clear. On the whole, the results reported here are similar to those of other small firm studies, yet vary markedly from large firm equivalents; suggesting that the nature of the returns to innovation may be contingent, at least in part, upon firm size. Moreover, the high levels of variation in firm performance should caution us against proffering innovative imperatives. If we are to counsel firms to "innovate at all costs", we must be clear about, and clearly demonstrate, the nature of the returns they may reasonably expect and the processes through which these may be optimised.
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  • 27
    ISSN: 1572-9737
    Keywords: conservation genetics ; Equus ; evolution ; mitochondrial DNA control region ; mitochondrial 12S rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolution, taxonomy and conservation of the genus Equuswere investigated by examining the mitochondrial DNA sequences of thecontrol region and 12S rRNA gene. The phylogenetic analysis of thesesequences provides further evidence that the deepest node in thephylogeny of the extant species is a divergence between twolineages; one leading to the ancestor of modern horses (E.ferus, domestic and przewalskii) and the other to thezebra and ass ancestor, with the later speciation events of the zebrasand asses occurring either as one or more rapid radiations, or withextensive secondary contact after speciation. Examination of the geneticdiversity within species suggested that two of the E. hemionussubspecies (E. h. onager and E. h. kulan) onlyrecently diverged, and perhaps, are insufficiently different to beclassified as separate subspecies. The genetic divergence betweendomestic and wild forms of E. ferus (horse) and E.africanus (African ass) was no greater than expected within anequid species. In E. burchelli (plains zebra) there was anindication of mtDNA divergence between populations increasing withdistance. The implications of these results for equid conservation arediscussed and recommendations are made for conservation action.
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  • 28
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    Journal of the history of biology 33 (2000), S. 457-491 
    ISSN: 1573-0387
    Keywords: J. B. S. Haldane ; biology ; politics ; genetics ; evolution ; population genetics ; physiology ; Darwinism ; experimental biology ; eugenics ; Britain ; Russia ; India ; Soviet ; Communism ; socialism ; philosophy ; vision ; literature ; popularization ; religion ; human experimentation ; bioethics ; Venus ; Mars ; science fiction ; technocracy ; futurology ; H. G. Wells ; Julian Huxley ; Olaf Stapledon ; C. S. Lewis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , History
    Notes: Abstract This paper seeks to reinterpret the life and work of J. B. S. Haldane by focusing on an illuminating but largely ignored essay he published in1927, “The Last Judgment” – the sequel to his better known work, Daedalus (1924). This astonishing essay expresses a vision of the human future over the next 40,000,000 years, one that revises and updates Wellsian futurism with the long range implications of the “new biology” for human destiny. That vision served as a kind of lifelong credo, one that infused and informed his diverse scientific work, political activities, and popular writing, and that gave unity and coherence to his remarkable career.
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  • 29
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    Journal of the history of biology 33 (2000), S. 221-246 
    ISSN: 1573-0387
    Keywords: August Weismann ; ciliates ; Clifford Dobell ; cytology ; death ; Emile Maupas ; evolution ; Herbert Spencer Jennings ; Otto Bütschli ; Paramecium ; rejuvenescence ; sex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , History
    Notes: Abstract In the period 1875–1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end.
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    Development genes and evolution 210 (2000), S. 644-650 
    ISSN: 1432-041X
    Keywords: Keywords Pax protein ; Paired domain ; Homeobox ; Transposase ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pax proteins play a diverse role in early animal development and contain the characteristic paired domain, consisting of two conserved helix-turn-helix motifs. In many Pax proteins the paired domain is fused to a second DNA binding domain of the paired-like homeobox family. By amino acid sequence alignments, secondary structure prediction, 3D-structure comparison, and phylogenetic reconstruction, we analyzed the relationship between Pax proteins and members of the Tc1 family of transposases, which possibly share a common ancestor with Pax proteins. We suggest that the DNA binding domain of an ancestral transposase (proto-Pax transposase) was fused to a homeodomain shortly after the emergence of metazoans about one billion years ago. Using the transposase sequences as an outgroup we reexamined the early evolution of the Pax proteins. Our novel evolutionary scenario features a single homeobox capturing event and an early duplication of Pax genes before the divergence of porifera, indicating a more diverse role of Pax proteins in primitive animals than previously expected.
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    Development genes and evolution 210 (2000), S. 82-91 
    ISSN: 1432-041X
    Keywords: Key words T-box genes ; Zebrafish ; Fins ; Evolution ; Gene duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The presence of two sets of paired appendages is one of the defining features of jawed vertebrates. We are interested in identifying genetic systems that could have been responsible for the origin of the first set of such appendages, for their subsequent duplication at a different axial level, and/or for the generation of their distinct identities. It has been hypothesized that four genes of the T-box gene family (Tbx2–Tbx5) played important roles in the course of vertebrate limb evolution. To test this idea, we characterized the orthologs of tetrapod limb-expressed T-box genes from a teleost, Danio rerio. Here we report isolation of three of these genes, tbx2, tbx4, and tbx5. We found that their expression patterns are remarkably similar to those of their tetrapod counterparts. In particular, expression of tbx5 and tbx4 is restricted to pectoral and pelvic fin buds, respectively, while tbx2 can be detected at the anterior and posterior margins of the outgrowing fin buds. This, in combination with conserved expression patterns in other tissues, suggests that the last common ancestor of teleosts and tetrapods possessed all four of these limb-expressed T-box genes (Tbx2–Tbx5), and that these genes had already acquired, and have subsequently maintained, their gene-specific functions. Furthermore, this evidence provides molecular support for the notion that teleost pectoral and pelvic fins and tetrapod fore- and hindlimbs, respectively, are homologous structures, as suggested by comparative morphological analyses.
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    Environmental geology 39 (2000), S. 360-371 
    ISSN: 1432-0495
    Keywords: Key words Environmental geophysics ; Resistivity ; Inversion ; Landfill mining ; Waste ; Characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Geophysical investigations using 2-D DC resistivity were carried out on old parts of two similar landfills, with waste of different ages. The data sets, which included high data density in both vertical and horizontal directions, were interpreted with 2-D smoothness constrained inversion. The landfills were excavated after the surveying. The objective was to test the capability of the resistivity method as a pre-characterization technique. The objectives were only partially fulfilled. First, the moisture content was the parameter that appeared to exert the dominant control over the resistivity distribution of the landfill. The most important potential information that can be recovered is, therefore, an indication of the waste piles hydraulics. Second, it was neither possible to estimate the amount of recoverable soils, nor to correlate the type of waste with the resistivity models. However, discrete anomalies were identified, and if specific materials are searched for, the resistivity models indicate possible places to search.
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    Development genes and evolution 210 (2000), S. 329-336 
    ISSN: 1432-041X
    Keywords: Key words Development ; Evolution ; Notch ; Insect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Studies of somitogenesis in vertebrates have identified a number of genes that are regulated by a periodic oscillator that patterns the pre-somitic mesoderm. One of these genes, hairy, is homologous to a Drosophila segmentation gene that also shows periodic spatial expression. This, and the periodic expression of a zebrafish homologue of hairy during somitogenesis, has suggested that insect segmentation and vertebrate somitogenesis may use similar molecular mechanisms and possibly share a common origin. In chicks and mice expression of the lunatic fringe gene also oscillates in the presomitic mesoderm. Fringe encodes an extracellular protein that regulates Notch signalling. This, and the finding that mutations in Notch or its ligands disrupt somite patterning, suggests that Notch signalling plays an important role in vertebrate somitogenesis. Although Notch signalling is not known to play a role in the formation of segments in Drosophila, we reasoned that it might do so in other insects such as the grasshopper, where segment boundaries form between cells, not between syncytial nuclei as they do in Drosophila. Here we report the cloning of a single fringe gene from the grasshopper Schistocerca. We show that it is not detectably expressed in the forming trunk segments of the embryo until after segment boundaries have formed. We conclude that fringe is not part of the mechanism that makes segments in Schistocerca. Thereafter it is expressed in a pattern which shows that it is a downstream target of the segmentation machinery and suggests that it may play a role in segment morphogenesis. Like its Drosophila counterpart, Schistocerca fringe is also expressed in the eye, in rings in the legs, and during oogenesis, in follicle cells.
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  • 34
    ISSN: 1432-0819
    Keywords: Stratigraphy ; Evolution ; El Chichón ; México
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 abundance and depletion in MgO, CaO, TiO2, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization.
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  • 35
    ISSN: 1432-1211
    Keywords: Key words KIR ; Multigene family ; Gene duplication ; Evolution
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    Topics: Biology , Medicine
    Notes: Abstract. Natural killer (NK) immunoglobulin-like receptors (KIRs) are a family of polymorphic receptors which interact with specific motifs on HLA class I molecules and modulate NK cytolytic activity. In this study, we analyzed a recently sequenced subgenomic region on chromosome 19q13.4 containing eight members of the KIR receptor repertoire. Six members are clustered within a 100-kb continuous sequence. These genes include a previously unpublished member of the KIR gene family 2DS6, as well as 2DL1, 2DL4, 3DL1, 2DS4, 3DL2, from centromere to telomere. Two additional KIR genes, KIRCI and 2DL3, which may be located centromeric of this cluster were also analyzed. We show that the KIR genes have undergone repeated gene duplications. Diversification between the genes has occurred postduplication primarily as a result of retroelement indels and gene truncation. Using pre- and postduplication Alu sequences identified within these genes as evolutionary molecular clocks, the evolution and duplication of this gene cluster is estimated to have occurred 30–45 million years ago, during primate evolution. A proposed model of the duplication history of the KIR gene family leading to their present organization is presented.
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  • 36
    ISSN: 1432-1211
    Keywords: Key words Vβ13 ; CD4/CD8 ratio ; Rat ; Tcrb ; Polymorphism
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    Topics: Biology , Medicine
    Notes: Abstract. Three rat BV13S1 alleles (T-cell receptor β-chain variable gene 13) were characterized by new BV13S1-allele specific monoclonal antibodies (18B1 and 17D5) and sequence analysis of expressed and genomic BV13S1. Two alleles were functional and designated BV13S1A1 present in strains LEW, BUF, PVG, and BV13S1A2 present in BN and WF. Their products differed by six amino acids, two of them in complementarity-determing region (CDR)1 and one in CDR2. A third nonfunctional allele, BV13S1A3P, was found in strains F344 and DA. Apart from a single nucleotide insertion, it was identical to BV13S1A2. All 12 rat strains tested showed association of TCRBC1 with BV8S2/4 alleles but not with the BV13S1 alleles, which may reflect a different gene order of the rat BV compared to mouse. BV13S1A1-encoded T-cell receptors (TCRs) which bind both monoclonal antibody (mAb) 18B1 and mAb 17D5 are over-represented in the CD4 lymphocyte subset. BV13S1A2-encoded TCRs which are stained by mAb 18B1 but not by mAb 17D5 show a slight CD8-biased expression. Preferential usage of BV13S1A1-positive TCRs by CD4 but not by CD8 cells in (LEW×WF)F1 hybrids and cosegregation of BV13SA1 and increased frequency of BV13S1 TCR-positive CD4 cells in a (LEW×BN)×BN backcross suggest structural differences of the two allelic products as the reason for their contrasting CD4/CD8 subset bias.
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    Immunogenetics 51 (2000), S. 69-74 
    ISSN: 1432-1211
    Keywords: Key words MHC class I ; Pseudogene ; Evolution ; Gorilla ; Chimpanzee
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  • 38
    ISSN: 1432-1211
    Keywords: Key words Immunoglobulin ; Fugu ; VH family ; Teleosts ; Evolution
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    Topics: Biology , Medicine
    Notes: Abstract. The variable region of the immunoglobulin heavy chain is created by a somatic rearrangement of a limited number of germline genes. This mechanism of gene assembly [V(D)J recombination] has been found to take place only in jawed vertebrates (gnathostomes). To understand how this mechanism evolved and diversified it is necessary to study the genomic organization of the heavy-chain gene in different vertebrate lineages. Since there is scant sequence information on the VH locus in fish, shotgun sequencing of a cosmid clone containing part of the VH genomic region of the Japanese pufferfish, Fugu rubripes, was undertaken. Eight full-length VH genes were isolated and characterized. They have higher homology to trout genes, but show the same structural features as VHs found in other vertebrates. Two VH subgroups have been identified whose members are interspersed. The frequency of synonymous and nonsynonymous substitution for VH comparisons between family members was found to be higher in the complementarity-determining regions than in the framework regions. Finally, there are four other genes interspersed with the VH genes, one of which is the first full-length retrotransposon element characterized in vertebrates.
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  • 39
    ISSN: 1432-1211
    Keywords: Key words J chain ; Polymeric immunoglobulin ; Ontogeny ; Evolution ; Comparative immunology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The J chain is a component of polymeric immunoglobulin (Ig) molecules and may play an important role in their polymerization and the transport of polymeric Ig across epithelial cells. In this study, the primary structure of the chicken J chain was determined by sequencing cDNA clones. The cDNA had an open reading frame of 476 nucleotides encoding a putative protein of 158 amino acid residues including the signal sequence. The 3′ untranslated region consisted of 1216 nucleotides and a poly(A) tail. The deduced amino acid sequence of the chicken J chain had a high degree of homology to that of human, cow, rabbit, mouse, frog, and earthworm, with eight conserved Cys residues identical to the mammalian J chains. Northern blot hybridization performed with total RNA from various chicken tissues revealed high levels of J-chain mRNA expression in spleen, intestine, Harderian gland, and bursa of Fabricius, and low levels in the thymus. The J chain was expressed in the bursa as early as day 15 of embryogenesis. These data indicated that the chicken J-chain gene displays a high degree of homology with that of other species, and is expressed at an early stage of development of the chicken immune system.
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  • 40
    ISSN: 1432-119X
    Keywords: Endothelin-A receptor ; Endothelin-B receptor ; Rat ; Pulmonary fibrosis ; Immunohistochemistry ; Quantitative PCR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: AbstractPulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ETB receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ETA and ETB receptor mRNA, and ETA receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ETA nor ETB receptor mRNA which were also not induced by bleomycin. We conclude that, while ETB receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ETA receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.
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    Oecologia 123 (2000), S. 330-341 
    ISSN: 1432-1939
    Keywords: Key words  Arabidopsis thaliana ; Carbon dioxide ; Evolution ; Reproduction ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene and is projected to increase from 36 to 70 Pa CO2 before the end of the 21st century. High pCO2 often increases the growth and reproduction of C3 annuals, whereas low pCO2 decreases growth and may reduce or prevent reproduction. Previous predictions regarding the effects of high and low pCO2 on C3 plants have rarely considered the effects of evolution. Knowledge of the potential for evolution of C3 plants in response to CO2 is important for predicting the degree to which plants may sequester atmospheric CO2 in the future, and for understanding how plants may have functioned in response to low pCO2 during the Pleistocene. Therefore, three studies using Arabidopsis thaliana as a model system for C3 annuals were conducted: (1) a selection experiment to measure responses to selection for high seed number (a major component of fitness) at Pleistocene (20 Pa) and future (70 Pa) pCO2 and to determine changes in development rate and biomass production during selection, (2) a growth experiment to determine if the effects of selection on final biomass were evident prior to reproduction, and (3) a reciprocal transplant experiment to test if pCO2 was a selective agent on Arabidopsis. Arabidopsis showed significant positive responses to selection for high seed number at both 20 and 70 Pa CO2 during the selection process. Furthermore, plants selected at 20 Pa CO2 performed better than plants selected at 70 Pa CO2 under low CO2 conditions, indicating that low CO2 acted as a selective agent on these annuals. However, plants selected at 70 Pa CO2 did not have significantly higher seed production than plants selected at 20 Pa CO2 when grown at high pCO2. Nevertheless, there was some evidence that high CO2 may also be a selective agent because changes in development rate and biomass production during selection occurred in opposite directions at low and high pCO2. Plants selected at high pCO2 showed no change or reductions in biomass relative to control plants due to a decrease in the length of the life cycle, as indicated by earlier initiation of flowering and senescence. In contrast, selection at low CO2 resulted in an average 35% increase in biomass production, due to an increase in the length of the life cycle that resulted in a longer period for biomass accumulation before senescence. From the Arabidopsis model system we conclude that some C3 annuals may have produced greater biomass in response to low pCO2 during the Pleistocene relative to what has been predicted from studies exposing a single generation of C3 plants to low pCO2. Furthermore, C3 annuals may exhibit evolutionary responses to high pCO2 in the future that may result in developmental changes, but these are unlikely to increase biomass production. This series of studies shows that CO2 may potentially act as a selective agent on C3 annuals, producing changes in development rate and carbon accumulation that could not have been predicted from single-generation studies.
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  • 42
    ISSN: 1432-0983
    Keywords: Key words Arbuscular mycorrhizas ; Evolution ; Glomus mosseae ; Plasma membrane H+-ATPase genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To identify genes that encode plasma membrane H+-ATPases in the arbuscular mycorrhizal fungus Glomus mosseae two sets of degenerate primers matching highly conserved motifs present in all plant and fungal ATPases were designed. Nested PCR-amplification of G. mosseae genomic DNA using the designed degenerate primers was carried out. Sequence analysis of the cloned PCR products identified five different clones (GmHA1, GmHA2, GmHA3, GmHA4 and GmHA5) encoding putative plasma membrane H+-ATPases. Comparison of the deduced amino-acid sequences of GmHA1–GmHA5 indicate that GmHA1, GmHA3 and GmHA4 are highly identical, while GmHA2 and GmHA5 are more divergent. The evolutionary and functional significance of the divergence found among the different members of the H+-ATPase gene family in G. mosseae is discussed.
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  • 43
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    Journal of population economics 13 (2000), S. 403-424 
    ISSN: 1432-1475
    Keywords: JEL classification: O41 ; F22 ; Key words: Altruism ; education ; growth ; convergence ; capital mobility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Sociology , Economics
    Notes: Abstract. The aim of this paper is to discuss the process of regional convergence within the framework of an overlapping generations model in which the engine of growth is the accumulation of human capital. In particular, we consider different education funding systems and compare their performance in terms of growth rates and pace of convergence between two heterogeneous regions. The analysis suggests that the choice of a particular education system incorporates a possible trade-off between long run growth rate and short run convergence. In such choice, the initial capital stock and the extent of regional human capital discrepancy appear as central variables.
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  • 44
    ISSN: 1432-2242
    Keywords: Key words Cicer species ; Microsatellites ; Zero-allele ; Phylogenetic tree ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The conservation of 90 microsatellite-flanking sequences from chickpea in 39 accessions of eight annual and 1 accession of a perennial species of the genus Cicer was investigated. All of the primer sequences successfully amplified microsatellites in related species, indicating the conservation of microsatellite-flanking sequences in chickpea’s relatives. However, the degree of conservation of the primer sites varied between species depending on their known phylogenetic relationship to chickpea, ranging from 92.2% in C. reticulatum, chickpea’s closest relative and potential ancestor, down to 50% for C. cuneatum. A phylogenetic tree revealed that chickpea and the other members of its crossability group were more closely related to the perennial C. anatolicum than to other annual species of the genus. Considerable variation in size and number of amplification products between and within species was observed. Sequence analysis of highly divergent amplification products proved that variation is either due to large differences in the number of microsatellite repeats or to the amplification of a locus unrelated to the one amplified from chickpea. Sequence information and bootstrapping using PAUP suggested that STMSs derived from chickpea may be efficiently and reliably used for synteny studies in chickpea’s crossability group, including C. anatolicum. However, care should be taken when applying these markers to other species of the genus. Considering the data presented here and the known historical record, the age of section Monocicer, including chickpea, is estimated to be about 100,000 years.
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  • 45
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    Theoretical and applied genetics 100 (2000), S. 1267-1273 
    ISSN: 1432-2242
    Keywords: Keywords Domestication ; Evolution ; QTL ; Map-based cloning ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The seeds of domesticated plants are normally much larger than those of their wild counterparts. This change in seed weight was most likely in response to the selection pressure for yield, uniform germination and seedling vigor which was exerted by humans during domestication. However, despite the evolutionary and agronomic significance of seed weight, very little is know about the genetic and developmental controls of this trait; and, thus far, none of the genes in this pathway have been isolated from any plant species. QTL mapping experiments conducted in tomato during the past decade have allowed the identification of many seed-weight QTLs and have also revealed that only a few loci are responsible for the majority of the seed-weight changes that accompanied the domestication of tomato. This review presents a consensus map for seed weight QTL identified in previously published reports and in unpublished results from our laboratory. This summary of seed-weight QTL data allows for the identification of the major loci controlling this trait in the genus Lycopersicon. It is hoped that this work will allow the elucidation of this important phenotypic transition that occurred during crop-plant domestication and will also provide the starting point for the cloning of a gene responsible for seed-weight variation.
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  • 46
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    Theoretical and applied genetics 101 (2000), S. 379-387 
    ISSN: 1432-2242
    Keywords: Key words Rice ; Isozyme variation ; Multilocus organization ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic organization of isozyme variation in rice (Oryza sativa L.) was investigated based on 17 polymorphic isozyme loci using a sample of 511 accessions of worldwide origin. The genetic diversity within the species was very high (H=0.36 with 4.82 alleles per locus), as compared with most selfing plant species. Three diversity centers were detected for isozyme variation including South Asia, China and Southeast Asia. The accessions were classified into three well-differentiated cultivar groups corresponding to the indica and japonica subspecies, and a new unnamed group. Variation within the cultivar groups accounted for 80% of the total isozyme variation. Within-country variation accounted for 58% of the total variation while among-region and among-country variation within the cultivar groups accounted for only 14% and 8% of the total variation. Analyses using log-linear models revealed that pronounced non-random associations between and among alleles at many unlinked isozyme loci were organized in a non-hierarchical pattern, and subspecific and macro-geographic differentiation was much more pronounced in multilocus phenotype frequencies than in allelic frequencies at individual loci. These results suggest that selection on multilocus gene complexes was largely responsible for the maintenance of the extensive isozyme variation within the species and the indica-japonica differentiation. Our results further suggest the independent domestication of indica and japonica, the dual origins of the indica rice from China and South Asia (India), and the differentiation of the ecotypes ’javanica’ and the ’temperate japonica’ within the japonica subspecies.
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  • 47
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    Theoretical and applied genetics 101 (2000), S. 1259-1268 
    ISSN: 1432-2242
    Keywords: Key words Enriched-library ; SSR ; Repetitive elements ; Allelic diversity ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsatellites have many desirable marker properties. There has been no report of the development and utilization of microsatellite markers in oat. The objectives of the present study were to construct oat microsatellite-enriched libraries, to isolate microsatellite sequences and evaluate their level of polymorphism in Avena species and oat cultivars. One hundred clones were isolated and sequenced from three oat microsatellite-libraries enriched for either (AC/TG) n , (AG/TC) n or (AAG/TTC) n repeats. Seventy eight clones contained microsatellites. A database search showed that 42% of the microsatellite flanking sequences shared significant homology with various repetitive elements. Alu and retrotransposon sequences were the two largest groups associated with the microsatellites. Forty four primer sets were used to amplify the DNA from 12 Avena species and 20 Avena sativa cultivars. Sixty two percent of the primers revealed polymorphism among the Avena species, but only 36% among the cultivars. In the cultivars, the microsatellites associated with repetitive elements were less polymorphic than those not associated with repetitive elements. Only 25% of the microsatellites associated with repetitive elements were polymorphic, while 46% of the microsatellites not associated with repetitive elements showed polymorphism in the cultivars. An average of four alleles with a polymorphism information content (PIC) of 0.57 per primer set was detected among the Avena species, and 3.8 alleles with a PIC of 0.55 among the cultivars. In addition, 54 barley microsatellite primers were tested in Avena species and 26% of the primers amplified microsatellites from oat. Using microsatellite polymorphisms, dendrograms were constructed showing phylogenetic relationships among Avena species and genetic relationships among oat cultivars.
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  • 48
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    Ecological research 15 (2000), S. 101-106 
    ISSN: 1440-1703
    Keywords: comparative ecology ; growth ; marine fish ; patterns ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: A number of strong regularities characterize certain very basic biological parameters in marine fishes. For example, the ovulated eggs of fish usually measure approximately 1 mm in diameter. The small, relatively uniform size of the eggs means that almost all fish larvae experience environmental variability at very similar scales, which itself establishes strong constraints for, and links between reproduction and recruitment. Additional constraints emerge from seawater being a poor medium for respiration, which establishes further linkages between growth and mortality. These constraints have produced strongly convergent features, and thence the patterns in reproduction and growth of marine fishes that are presented.
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  • 49
    ISSN: 1573-143X
    Keywords: body composition ; catfish (Mystus nemurus) ; feeding rate ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P 〉 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P 〉 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.
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    Aquaculture international 8 (2000), S. 531-542 
    ISSN: 1573-143X
    Keywords: feed intake ; growth ; protein utilisation ; proximate ; composition ; rainbow trout (Oncorhynchus mykiss)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rainbow trout Oncorhynchus mykiss grew from 44 to 326 g in 96days when held at ∼12 °C. Fish were fed to satiation twice dailywith either high (L1: 30.8%, L2:31.4%) or lower-lipid feeds (C1: 18.8%,C2: 21.8%). Four feeding treatments were studied.Group C1C2 received feed C1 for 43 days(days 0–43) and C2 thereafter (days 44–96).Groups L1L2, L1C2 andC1L2 were subjected to dietary changes asindicated by the feed designations. After a short period of feedadaptation, fish ingested similar amounts of feed energy i.e., they ateless by weight of the lipid-rich (L) feeds. Feed lipid content did notaffect growth but fish fed L-feed had reduced feed conversion ratio(FCR) compared to fish fed C-feed (0.731 vs. 0.773) during days0–43 (P 〈 0.01). After 96 days,L1L2-fish were lower in body protein(15.8%) than the C1C2-fish (16.8%)(P 〈 0.01). L-feeds also tended to increase percentage lipidand reduce percentage whole body moisture and ash. A higher net proteinutilisation (NPU) was recorded in fish fed L-feeds (43.6%)compared to fish fed C-feeds (38.8%) in days 0–43(P 〈 0.05). This seemed to be the result of a lower proteinintake rather than a protein-sparing effect of feed lipid. Above athreshold value of approximately 6.5 mg protein eaten·g bodywtminus 1·day−1, NPU decreased.
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  • 51
    ISSN: 1573-143X
    Keywords: aggression ; Atlantic salmon (Salmo salar) ; dominance ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Aggression in groups of 0+ Atlantic salmon (Salmo salar) was monitoredat weekly intervals in two tanks containing 100 fish each. Three 1 + salmonparr were added to one of these. After 5 weeks, fish weights were measuredin both tanks and the conditions reversed. At ten weeks, weights of fish inboth tanks were measured again. In both populations, levels of aggressionamong the smaller fish were significantly lower and growth ratessignificantly higher when the large fish were present. Although the largefish attacked the small ones, the rate at which they did so was an order ofmagnitude lower that the rate at which small fish attacked each other in theabsence of larger conspecifics. This raises the possibility that levels ofaggression among farmed salmon might be reduced by the addition of a fewlarge conspecifics.
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  • 52
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    Journal of chemical ecology 26 (2000), S. 2015-2023 
    ISSN: 1573-1561
    Keywords: Allelopathy ; growth ; phenolics ; Hebeloma ; Hymenoscyphus ; Picea abies ; Vaccinium myrtillus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Allelopathy due to humus phenolics is a cause of natural regeneration deficiency in subalpine Norway spruce (Picea abies) forests. If inhibition of spruce germination and seedling growth due to allelochemicals is generally accepted, in contrast there is a lack of knowledge about phenolic effects on mycorrhizal fungi. Thus, this work tested effects of a humic solution and its naturally occurring phenolics on the growth and respiration of two mycorrhizal fungi: Hymenoscyphus ericae (symbiont of Vaccinium myrtillus, the main allelochemical-producing plant) and Hebeloma crustuliniforme (symbiont of P. abies, the target plant). Growth and respiration of H. crustuliniforme were inhibited by growth medium with the original humic solution (−6% and −30%), respectively, whereas the same humic solution did not affect growth but decreased respiration of H. ericae (−55%). When naturally occurring phenolics (same chemicals and concentrations in the original humic solution) were added to the growth medium, growth of H. crustuliniforme was not affected, whereas that of H. ericae significantly increased (+10%). We conclude that H. ericae is better adapted to the allelopathic constraints of this forest soil than H. crustuliniforme and that the dominance of V. myrtillus among understory species could be explained in this way.
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  • 53
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    The environmentalist 20 (2000), S. 257-271 
    ISSN: 1573-2991
    Keywords: evolution ; tides ; sea level ; time series
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The increasing use of computers since the 1960s, has implied the digitization of observations in meteorology, oceanography and other observational sciences. Enough data has been accumulated to suggest that some patterns of evolution in the world may be discernable. The present article deals with what appears as changing tides around Canada.
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  • 54
    ISSN: 1573-4927
    Keywords: ancient endogenous provirus ; evolution ; retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A new family of murine endogenous proviruses (VL6.0) is described here. The intact provirus is near 6 kb in length and shows a genomic organization of 5" LTR, gag, pol, env, and 3" LTR. The primer binding site (PBS) is that of a tRNAgly. The lack of functional open reading frames and occurrence of significant gaps in most, if not all, members of this group show it to be ancient. Our estimate of copy number per haploid genome is 30+. Members of this group have been isolated from Mus musculus domesticus, M. m. casteneus, M. m. hortulanus, M. caroli, and M. spretus. The occurrence of these sequences throughout such diverse members of the genus Mus may indicate that the date of the original infection predated the divergence of the extant Mus lineages at around 2.5 million years ago. Analysis of gap (deletion/insertion) patterns indicates that these sequences may have proliferated within the Mus genome by a mechanism of reverse transcriptase-mediated transposition. As yet, there are no closely related murine retroviruses described. The closest mammalian retrovirus based on sequence similarity is from the miniature swine (Sus scrofa).
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  • 55
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    Behavioral ecology and sociobiology 49 (2000), S. 48-56 
    ISSN: 1432-0762
    Keywords: Keywords Antipredator behavior ; Phylogenetic inertia ; Conflicting selection pressures ; Evolution ; Salamanders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The streamside salamander, Ambystoma barbouri, exhibits ineffective antipredator behavior (high emergence rate from refuge, and high activity while out of refuge) and thus suffers heavy predation in stream pools with sunfish. A. barbouri evolved relatively recently from an ancestor that closely resembled a sister species, A. texanum, which breeds in fishless, ephemeral ponds. Sunfish thus represent a relatively new selection pressure for A. barbouri. Phylogenetic inertia predicts that (1) A. texanum should be very poor at coping with fish and (2) because it has only recently been exposed to fish, A. barbouri should still be poor at avoiding fish, but due to its recent exposure to fish, A. barbouri should be better than A. texanum at coping with sunfish. Experimental results provided mixed support for these predictions. As predicted, A. texanum suffered heavy sunfish predation. Compared to A. texanum, A. barbouri showed a greater tendency to initiate alarm moves that enhanced escape success from fish. However, in both the presence and absence of fish, A. barbouri showed higher emergence rates from refuge and higher movement while out of refuge than A. texanum. These behaviors tend to increase exposure to sunfish, i.e., for these key behaviors, A. barbouri apparently evolved in the wrong direction as far as fish predation is concerned. Due to these offsetting effects (increased exposure to fish, increased escape success), A. barbouri is no better at surviving with sunfish than A. texanum. A possible explanation for the high activity of A. barbouri is its use of highly ephemeral habitats (relative to A. texanum) that favor the evolution of higher activity, feeding, and developmental rates for A. barbouri relative to A. texanum.
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  • 56
    ISSN: 1617-4623
    Keywords: Key wordsDrosophila melanogaster ; Ceratitis capitata ; Tephritids ; Evolution ; Dacus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alcohol dehydrogenase genes make up one of the best studied gene families in Drosophila, both in terms of expression and evolution. Moreover, alcohol dehydrogenase genes constitute potential versatile markers in insect transformation experiments. However, due to their rapid evolution, these genes cannot be cloned from other insect genera by DNA hybridization or PCR-based strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast genes have evolved independently, acquiring their enzymatic function convergently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementation in yeast can be used to clone alcohol dehydrogenase genes that are unrelated in sequence to those of yeast, thus providing a powerful tool for isolation of dominant insect transformation marker genes.
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  • 57
    ISSN: 1617-4623
    Keywords: Key wordsDictyostelium discoideum ; Mitochondrial DNA ; Genome sequencing ; Genetic map ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identified genes include those for two ribosomal RNAs (rnl and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and five other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used. (2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sufficient to support the synthesis of mitochondrial protein. (4) In total, five group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.
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  • 58
    ISSN: 1618-2545
    Keywords: biogeography ; calmodulin ; DNA sequence ; elongation factor EF-1α ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phylogenetic relationships within theGibberella fujikuroi species complex were extended to newly discovered strains using nucleotide characters obtained by sequencing polymerase chain reaction (PCR) amplified DNA from 4 loci used in a previous study [nuclear large subunit 28S rDNA, nuclear ribosomal internal transcribed spacer (ITS) region, mitochondriaal small subunit (mtSSU) ribosomal DNA, and β-tubulin] together with two newly sampled protein-encoding nuclear genes, translation elongation factor EF-1α and calmodulin. Sequences from the ribosomal ITS region were analyzed separately and found to contain of two highly divergent, nonorthologous ITS2 types. Phylogenetic analysis of the individual and combined datasets identified 10 new phylogenetically distinct species distributed among the following three areas: 2 within Asia and 4 within both Africa and South America. Hypotheses of the monophyly ofFusarium subglutinans and its two formae speciales, f. sp.pini and f. sp.ananas, were strongly rejected by a likelihood analysis. Maximum parsimony results further indicate that the protein-encoding nuclear genes provide considerably more phylogenetic signal that the ribosomal genes sequenced. Relative apparent synapomorphy analysis was used to detect long-branch attraction taxa and to obtain a statistical measure of phylogenetic signal in the individual and combined datasets.
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  • 59
    ISSN: 1618-2545
    Keywords: Ascomycota ; evolution ; pyrenomycetes ; systematics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate the systematic position of the unitunicate pyremomycetePapulosa amerospora, we performed phylogenetic analyses of SSU rDNA sequences from 37 ascomycetes. Among these sequences were some new ones from taxa that might be related toPapulosa: Hyponectriaceae (Hyponectria buxi, Monographella nivalis), Phyllachorales (Phyllachora graminis), and Xylariales (Barrmaelia melanotes, Poronia punctata). Our results showed 100% bootstrap support for a clade of all unitunicate pyrenomycetes, the class Sordariomycetes. We also found strong support for recognizing the subclasses Hypocreomycetidae and Xylariomycetidae. The remaining taxa, belonging to subclass Sordariomycetidae, appeared as a polyphyletic group in one analysis, but was monophyletic when shorter SSU sequences were used.Barrmaelia melanotes, Poronia punctata, Hyponectria buxi, andMonographella nivalis are members of Xylariomycetidae, but we could not determine whetherMonographella should be included in Hyponectriaceae. The new family Papulosaceae is erected forPapulosa on molecular and morphological bases, but the exact systematic position ofPapulosa within subclass Sordariomycetidae is still uncertain, since the genus did not cluster consistently with any of the included taxa. Phyllachorales are not closely related to Diaporthales, as previously suggested.
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  • 60
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    Artificial life and robotics 4 (2000), S. 109-118 
    ISSN: 1614-7456
    Keywords: Parallel and distributed processing ; Space navigation ; Evolution ; WAVE model ; Cooperative behavior ; Mobile robots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper modifies the WAVE model for parallel processing in virtual networks to explore and process continuous physical worlds. Expressing distributed activity by cooperative jobs spreading in space and “seeing” each other, rather than as vehicles exchanging messages, the model allows complex missions to be planned in a very flexible manner, with mobile hardware being assigned to the evolving space-conquering programs (waves) dynamically, when required or available. A number of cooperative scenarios in a physical world demonstrate the simplicity and compactness of the wave code. The execution of waves by mobile hardware is discussed, including run-time mapping of waves to vehicles, and supporting multiple distributed jobs in cases of hardware shortages. WAVE can be used efficiently for solving complex problems in space by organized groups of cheap specialized mobile robots, where intelligent behavior is provided by very high level of system organization rather than by the smartness of individual units. In a broader sense, it may also serve as a basic technology for parallel and distributed simulation, and the management of evolution and self-organization of large open systems of different natures.
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  • 61
    ISSN: 1608-3237
    Keywords: poly-β-hydroxybutyric acid ; Yersinia pseudotuberculosis ; Listeria monocytogenes ; temperature ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparative investigation of the intracellular content of poly-β-hydroxybutyric acid showed that Yersinia pseudotuberculosis strains accumulated, on the average, lower amounts of this reserve substance than Listeria monocytogenes strains. The intracellular pool of poly-β-hydroxybutyric acid was responsible for the growth of the bacteria at low temperatures (4–6°C) in the absence of any exogenous carbon and energy source.
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  • 62
    ISSN: 1608-3407
    Keywords: Scenedesmus quadricauda ; growth ; cell size ; photosynthetic activity ; imazalil sulfate ; three-phase dose response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three-phase dose responses of biological systems of different levels of organization are often called “paradoxical” because the biological effects are clearly manifested under low- and high-intensity treatments, but are absent during moderate-strength treatments. In this work, we found anomalous changes in the cell number of a green alga Scenedesmus quadricauda (Turp.) Breb. grown in the presence of the fungicide imazalil sulfate. At low imazalil concentrations (2.5 × 10–9–2.5 × 10–6 M), the slow increase in the cell number as compared to an untreated culture was not related to cell death. As seen by the dynamics of the population structure and cell functional characteristics (photosynthesis, thermal stability of photosynthetic membranes, etc.), the decrease in the growth rate at low concentrations of imazalil (2–10 × 10–9 M) was due to a long-term arrest of cell division in a fraction of the cell population rather than to a decrease in the rate of division. The absence of a toxic effect or even a slight stimulation of culture growth at moderate concentrations (0.05–1.25 × 10–6 M) was due to the resumption of cell division after a temporal cessation. At these concentrations, imazalil induced cell stress and adaptive elevation of cell tolerance to the fungicide (acclimation). Cell death was observed only at a high fungicide content in the medium (6.25 × 10–6 and higher). Thus, the three-phase (bimodal) dose response corresponds to two regimes (steady-states) of cell functioning which differ in cell sensitivity to external stimuli. The low-sensitivity state, which is characteristic of cells that have experienced stress, is likely to be the state known as “hormesis.”
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  • 63
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    Journal of applied phycology 12 (2000), S. 185-189 
    ISSN: 1573-5176
    Keywords: blue-green alga ; cyanobacterium ; carbon dioxide ; culture ; growth ; Nostocflagelliforme ; rehydration, watering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The terrestrial blue-green alga (cyanobacterium), Nostoc flagelliforme, was cultured in air at variouslevels of CO2, light and watering to see theireffects on its growth. The alga showed the highestrelative growth rate at the conditions of highCO2 (1500 ppm), high light regime (219–414μmol m-2s-1) and twice daily watering,but the lowest rate at the conditions of low light(58–114 μmol m-2s-1) and daily twicewatering. Increased watering had little effect ongrowth rate at 350 ppm CO2, but increased byabout 70% at 1500ppm CO2 under high lightconditions. It was concluded that enriched CO2could enhance the growth of N. flagelliformewhen sufficient light and water was supplied.
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  • 64
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    Glycoconjugate journal 17 (2000), S. 465-483 
    ISSN: 1573-4986
    Keywords: N-acetylglucosaminyltransferases ; glycosylation ; glycoproteins ; Golgi complex ; evolution ; development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This review covers discoveries made over the past 30–35 years that were important to our understanding of the synthetic pathway required for initiation of the antennae or branches on complex N-glycans and O-glycans. The review deals primarily with the author's contributions but the relevant work of other laboratories is also discussed. The focus of the review is almost entirely on the glycosyltransferases involved in the process. The following topics are discussed. (1) The localization of the synthesis of complex N-glycan antennae to the Golgi apparatus. (2) The “evolutionary boundary” at the stage in N-glycan processing where there is a change from oligomannose to complex N-glycans; this switch correlates with the appearance of multicellular organisms. (3) The discovery of the three enzymes which play a key role in this switch, N-acetylglucosaminyltransferases I and II and mannosidase II. (4) The “yellow brick road” which leads from oligomannose to highly branched complex N-glycans with emphasis on the enzymes involved in the process and the factors which control the routes of synthesis. (5) A short discussion of the characteristics of the enzymes involved and of the genes that encode them. (6) The role of complex N-glycans in mammalian and Caenorhabditis elegans development. (7) The crystal structure of N-acetylglucosaminyltransferase I. (8) The discovery of the enzymes which synthesize O-glycan cores 1, 2, 3 and 4 and their elongation.
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  • 65
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    Journal of bioeconomics 2 (2000), S. 9-23 
    ISSN: 1573-6989
    Keywords: evolution ; altruism ; morality ; utilitarianism ; Marxism ; Rawls ; fairness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Economics
    Notes: Abstract Several evolutionary mechanisms have been identified in the literature that would generate altruism in humans. The most powerful (except for kin selection) and most controversial is group selection, as recently analyzed by Sober & D.S. Wilson. I do not take a stand on the issue of the existence of group selection. Instead, I examine the level of human altruism that could exist if group selection were an engine of human evolution. For the Sober & Wilson mechanism to work, groups practicing altruism must grow faster than other groups. I call altruistic behavior that would lead to faster growth ‘efficient altruism’. This often consists of cooperation in a prisoner's dilemma. ltruistic acts such as helping a temporarily hungry or injured person would qualify as efficient altruism. Efficient altruism would also require monitoring recipients to avoid shirking. Utilitarianism would be an ethical system consistent with efficient altruism, but Marxism or the Rawlsian system would not. Discussions of efficient altruism also help understand intuitions about fairness. We perceive those behaviors as ‘fair’ that are consistent with efficient altruism. It is important to understand that, even if humans are selected to be altruistic, the forms of altruism that might exist must be carefully considered and ircumscribed.
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  • 66
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    Biology and philosophy 15 (2000), S. 443-463 
    ISSN: 1572-8404
    Keywords: David Hull ; evolution ; selection
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    Topics: Biology , Philosophy
    Notes: Abstract One of the principal difficulties in assessing Science as aProcess (Hull 1988) is determining the relationship between the various elements of Hull's theory. In particular, it is hard to understand precisely how conceptual selection is related to Hull's account of the social dynamics of science. This essay aims to clarify the relation between these aspects of his theory by examining his discussion of the``demic structure'' of science. I conclude that the social account cando significant explanatory work independently of the selectionistaccount. Further, I maintain that Hull's treatment of the demicstructure of science points us toward an important set of issues insocial epistemology. If my reading of Science as a Process iscorrect, then most of Hull's critics (e.g., those who focus solelyon his account of conceptual selection) have ignored promisingaspects of his theory.
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  • 67
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    Biology and philosophy 15 (2000), S. 493-508 
    ISSN: 1572-8404
    Keywords: complexity ; entropy balance ; environment independence ; evolution ; information fundamental identity ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract Some real objects show a very particular tendency: that of becomingindependent with regard to the uncertainty of their surroundings. This isachieved by the exchange of three quantities: matter, energy andinformation. A conceptual framework, based on both Non-equilibriumThermodynamic and the Mathematical Theory of Communication is proposedin order to review the concept of change in living individuals. Three mainsituations are discussed in this context: passive independence inconnection with resistant living forms (such as seeds, spores, hibernation,...), active independence in connection with the life span of aliving individual (whether an ant or an ant farm), and the newindependence in connection with the general debate of biological evolution.
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    Biology and philosophy 15 (2000), S. 641-668 
    ISSN: 1572-8404
    Keywords: complexity ; evolution ; function ; modularity ; parts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract The functional complexity, or the number of functions, of organisms hasfigured prominently in certain theoretical and empirical work inevolutionary biology. Large-scale trends in functional complexity andcorrelations between functional complexity and other variables, such assize, have been proposed. However, the notion of number of functions hasalso been operationally intractable, in that no method has been developedfor counting functions in an organism in a systematic and reliable way.Thus, studies have had to rely on the largely unsupported assumption thatnumber of functions can be measured indirectly, by using number ofmorphological, physiological, and behavioral “parts” as a proxy. Here, amodel is developed that supports this assumption. Specifically, the modelpredicts that few parts will have many functions overlapping in them, andtherefore the variance in number of functions per part will be low. If so,then number of parts is expected to be well correlated with number offunctions, and we can use part counts as proxies for function counts incomparative studies of organisms, even when part counts are low. Alsodiscussed briefly is a strategy for identifying certain kinds of parts inorganisms in a systematic way.
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    Biology and philosophy 15 (2000), S. 713-732 
    ISSN: 1572-8404
    Keywords: Darwin ; error theory ; ethics ; evolution ; evolutionary ethics ; Mackie ; naturalistic fallacy ; Ruse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract Suppose that the human tendency to think of certain actions andomissions as morally required – a notion that surely lies at the heart of moral discourse – is a trait that has been naturallyselected for. Many have thought that from this premise we canjustify or vindicate moral concepts. I argue that this is mistaken, and defend Michael Ruse's view that the moreplausible implication is an error theory – the idea thatmorality is an illusion foisted upon us by evolution. Thenaturalistic fallacy is a red herring in this debate,since there is really nothing that counts as a ‘fallacy’ at all. If morality is an illusion, it appears to followthat we should, upon discovering this, abolish moraldiscourse on pain of irrationality. I argue that thisconclusion is too hasty, and that we may be able usefullyto employ a moral discourse, warts and all, withoutbelieving in it.
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  • 70
    ISSN: 1618-2545
    Keywords: Ascomycota ; evolution ; molecular clock ; plant pathogen ; powdery mildew
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phylogenetic relationships of Erysiphales within Ascomycota were inferred from the newly determined sequences of the 18S rDNA and partial sequences of the 28S rDNA including the D1 and D2 regions of 10 Erysiphales taxa. Phylogenetic analyses revealed that the Erysiphales form a distinct clade among ascomycetous fungi suggesting that the Erysiphales diverged from a single ancestral taxon. The Myxotrichaceae of the Onygenales was distantly related to the other onygenalean families and was the sister group to the Erysiphales calde, with which it combined to form a clade. The Erysiphales/Myxotrichaceae clade was also closely related to some discomycetous fungi (Leotiales, Cyttariales and Thelebolaceae) including taxa that form cleistothecial ascomata. The present molecular analyses as well as previously reported morphological observations suggest the possible existence of a novel evolutionary pathway from cleistothecial discomycetous fungi to Erysiphales and Myxotrichaceae. However, since most of these fungi, except for the Erysiphales, are saprophytic on dung and/or plant materials, the questions of how and why an obligate biotroph like the Erysiphales radiated from the saprophytic fungi remain to be addressed. We also estimated the radiation time of the Erysiphales using the 18S rDNA sequences and the two molecular clockes that have been previously reported. The calculation showed that the Erysiphales split from the Myxotrichaceae 190–127 myr ago. Since the radiation time of the Erysiphales does not exceed 230 myr ago, even when allowance is made for the uncertainty of the molecular clocks, it is possible to consider that the Erysiphales evolved after the radiation of angiosperms. The results of our calculation also showed that the first radiation within the Erysiphales (138–92 myr ago) coincided with the date of a major diversification of angiosperms (130–90 myr ago). These results may support our early assumption that the radiation of the Erysiphales coincided with the evolution of angiosperm plants.
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    Aquatic ecology 34 (2000), S. 19-27 
    ISSN: 1573-5125
    Keywords: adaptation ; fitness ; food quality ; growth ; reproduction ; temporary ponds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporary pond Daphnia flourish on relatively poor-quality food, suggesting adaptation to stringent temporary pond conditions. We conducted laboratory life history experiments on populations of Daphnia obtusa from a shaded woodland temporary pond (short hydroperiod, dystrophic) and an open farmland temporary pond (long hydroperiod, eutrophic), and compared a suite of physical/chemical conditions in the ponds to evaluate habitat conditions. We hypothesized that the shaded woodland pond population would be more fit in terms of life history variables for individuals (age and size at first reproduction, mean brood size, mean number of neonates) and populations (generation time, net reproductive rate R 0, and intrinsic reproductive rate r) given a standard, low-quality food (trout chow and yeast). Life history traits of woodland pond animals were mixed, relative to farm pond animals, and consistent with bet-hedging for an unpredictable habitat. Values of life history traits rivaled or exceeded those of other studies using phytoplankton as food, and were influenced by the pond water used for our study. Life histories clearly differ among local and regional temporary pond Daphnia obtusa populations, and should be valuable for examining the relative influences of local selection and metapopulation dynamics on population structure.
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  • 72
    ISSN: 1573-5176
    Keywords: desiccation ; growth ; growth model ; inorganic carbon ; nutrients ; photoperiod ; photosynthesis ; pigments ; Porphyra linearis ; PPF ; respiration ; temperature ; water velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 °C), low PPF (70–140 μmol photon m-2s-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.
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  • 73
    ISSN: 1573-5125
    Keywords: crayfish ; Procambarus alleni ; growth ; Florida Everglades ; hydroperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Environmental conditions influence crustacean growth by affecting molt intervals and incremental increases in length and weight. In the seasonally-flooded marl prairie wetlands of eastern Everglades National Park, U.S.A., hydropattern exerts considerable influence on aquatic primary productivity, and so may influence the availability of food resources for higher trophic levels. The seasonal hydroperiod has been drastically altered by anthropogenic factors, but the impacts on the aquatic community are not well known. We studied whether differences in growth of crayfish Procambarus alleni could be detected in habitats with different hydroperiods. We first described growth patterns based on incremental increases in length and weight of crayfish on a high protein diet in the laboratory. Regression analyses indicated that growth patterns in males and females were similar. Although the intermolt period increased with age, the proportional increases in length and weight were similar through successive molts. The relationship between length and weight of crayfish was best described by a power equation for allometric growth. We then compared growth curves for crayfish subpopulations from different areas of the marl prairie. In habitats with the longest hydroperiods, crayfish weight-at-size was not significantly different from that in laboratory crayfish on the high protein diet. However, weight gain per unit increase in length in short hydroperiod sites was significantly less than in long hydroperiod sites or in the laboratory. These results indicate that crayfish productivity may be associated with hydroperiod in these stressed wetlands, and this may contribute to observed source-sink population regulation.
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    Neural processing letters 11 (2000), S. 29-38 
    ISSN: 1573-773X
    Keywords: evolution ; online ; game ; neural ; network ; genetic ; real-time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In standard neuro-evolution, a population of networks is evolved in a task, and the network that best solves the task is found. This network is then fixed and used to solve future instances of the problem. Networks evolved in this way do not handle real-time interaction very well. It is hard to evolve a solution ahead of time that can cope effectively with all the possible environments that might arise in the future and with all the possible ways someone may interact with it. This paper proposes evolving feedforward neural networks online to create agents that improve their performance through real-time interaction. This approach is demonstrated in a game world where neural-network-controlled individuals play against humans. Through evolution, these individuals learn to react to varying opponents while appropriately taking into account conflicting goals. After initial evaluation offline, the population is allowed to evolve online, and its performance improves considerably. The population not only adapts to novel situations brought about by changing strategies in the opponent and the game layout, but it also improves its performance in situations that it has already seen in offline training. This paper will describe an implementation of online evolution and shows that it is a practical method that exceeds the performance of offline evolution alone.
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    Aquaculture international 8 (2000), S. 159-168 
    ISSN: 1573-143X
    Keywords: emersion ; growth ; Pecten maximus ; scallop spat ; survival ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Scallop spat production normally requires transfer between growthsystems. Simulated transport experiments were carried out in April, June,December and February to evaluate effects of transport time on greatscallop (Pecten maximus) spat growth and survival. The spat (1.7–1.8 mm in shell-height and 21–25 µg ash free dry weight [AFDW]) wereheld in moist coffee filters at a temperature of 10 °C for up to 24 h,before being replaced into sieves in rearing tanks at 15 °C. The studyshowed that by increasing air emersion time, survival and growthdecreased. No significant difference in the results between 0 and 4 h of airemersion was found, while the effects after 12 and 24 h differed betweenspat groups. Survival and growth rates showed seasonal differences. Meansurvival was 35–71% in April and 77–99% from June to February. In Junemean growth rates attained were 115–128 µm shell-height and 15–18µg AFDW per day compared with 49–69 µm and 3.8–7.0 µgper day for the other spat groups. Great scallop spat may survive atransfer time of 24 h, but transportation for longer than 12 h is notrecommended if subsequent high survival and growth rates are to beensured.
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    Aquaculture international 8 (2000), S. 207-225 
    ISSN: 1573-143X
    Keywords: growth ; mortality ; Pecten maximus ; suspended culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth and mortality of the king scallop, Pecten maximus, werecompared when grown in cages and by ear hanging in suspended culturein Fuengirola, Malaga, in southern Spain. Seed (juveniles) used in theexperiment was collected in September 1997 that had settled on collectorsin April-June, of that year. Culture in suspended cages began in January1998 when the seed measured 42.7 (3.3) mm shell height and ended inFebruary 1999. Significantly faster growth was found at a minimum culturedensity (16 scallops/cage) than at two other densities (24 and 36scallops/cage). Depth (1, 5 and 10 m from the bottom) influenced growth,poorest growth occurred closest to the bottom. Under optimum growingconditions, 16 scallops/cage suspended 10 m from the bottom, scallops grewto 10 cm shell length (legal size) by February 1999.In ear hanging culture, ropes were moored in April (51.3 (4.5) mm),June (58.2 (4.5) mm) and November 1998 (64.3 (4.9) mm).Initially, rapid shell growth was observed in all three cultures.Subsequently, the shells became covered with barnacles, Balanus sp.,that possibly caused total mortality of the April culture and led to highmortalities in the two other cultures.
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  • 77
    ISSN: 1573-143X
    Keywords: growth ; silver perch (Bidyanus bidyanus) ; size grading ; size variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study presents two experiments addressing growth and size variation in fingerling silver perch (Bidyanus bidyanus. In the first experiment, fish close to mean population size were raised either in the presence or absence of five larger fish for 60 days. Mean specific growth rate (SGR) and increases in the coefficient of variation and skewness were lower in the presence of larger fish, indicating a negative effect of large fish on the growth of smaller ones. In the second experiment, fingerlings were graded into groups smaller and larger than the median size of the population and raised in size-sorted groups of 60 large or small fish and mixed groups of 30 fish of each size category, for 60 days. There was no difference in mean SGR among groups, nor between the mixed group ad the weighted mean of the small and large groups. Biomass gain was higher in the mixed groups than in the weighted small-and-large groups, probably due to a slightly lower survival in the groups comprised of large fish. The fact that the effect of large fingerlings on the growth of smaller ones was evident in the first, but not the second, experiment may be attributed to higher size disparity between large and small fingerlings in the first experiment.
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  • 78
    ISSN: 1573-143X
    Keywords: 17 β-estradiol ; fish meal ; gonadal development ; growth ; Nile tilapia (Oreochromis niloticus) ; plant proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to evaluate theeffect of plant protein‐based diets on gonadaldevelopment and plasma 17 β-estradiol (E2) levelin female Nile tilapia Oreochromis niloticus.Fish with a mean body weight of 6.7 (0.1) g were fedfour different diets with the same digestible protein(DP) and digestible energy (DE) containing gradedlevels of a mixture of plant ingredients as partial ortotal replacement of fish meal protein for 20 weeks.The control diet (D0) was based on fish meal, twodiets containing 33% (D33) and 66% (D66) of plantprotein, and one diet containing only plant protein(D100). Fish were sampled at 12 and 20 weeks. Nosignificant differences were found in different stagesof oocyte development and plasma E2 levels betweentilapia fed diets D0 and D100 at 12 weeks. Eight weekslater tilapia fed diet D0 showed a higher (P 〈 0.05)level of E2 than the D100 group. This difference andthe reduced proportion of vitellogenic and matureoocytes demonstrated that diets containing only plantprotein are less efficient in terms of tilapia growthand consequently ovarian development.
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    Aquaculture international 8 (2000), S. 455-461 
    ISSN: 1573-143X
    Keywords: floating cages ; growth ; pink dentex (Dentex gibbosus) ; sparids (Dentex dentex, Sparus aurata, Spondyliosoma cantharus, Diplodus puntazzo)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Aquaculture international 7 (2000), S. 369-382 
    ISSN: 1573-143X
    Keywords: growth ; haddock (Melanogrammus aeglefinus) ; larvae ; light intensity ; photperiod ; tank colour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 μmol s−1 m−2 or 18 μmol s−1 m−2). Growth (0.8% day−1 in standard length; 2.9% day−1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 μmol s−1 m−2) light intensity (0.8% day−1 in standard length and 2.2% day−1 in body area versus 1.1% day 21 in standard length and 3.1% day−1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments.
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  • 81
    ISSN: 1573-143X
    Keywords: bivalve ; fouling ; growth ; Newfoundland ; nursery ; sea scallop (Placopecten magellanicus) ; spat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Hatchery-reared sea scallop (Placopecten magellanicus) spat weremonitored for growth and recovery in three experiments to determine themost suitable system for nursery culture. In Experiment I, four size classesof nursery-sized spat held at two depths from October to July exhibiteddeclining growth rates over the winter period and increased growth ratesin the spring. Overall, season, depth and initial size had a significantinfluence on the absolute and specific growth rates of scallops. Recovery,defined as number of scallops remaining after mortality and loss of spatthrough gear mesh, was influenced by season and initial size, but notdepth. Scallops in the 3.0 mm+ size class had higher growth rates andrecovery than those in the 1.4–1.6 mm, 1.7–1.9 mm and 2.0–2.9 mm sizeclasses. In Experiment II, two gear types containing similar size spat werecompared. Growth rates were significantly higher in 3.0 mm pearl nets thanin 3.0 mm collector bags, although recovery was similar between the twoequipment types. Experiment III, two stocking densities of nursery-sizedspat were compared in collector bags. Neither growth rate nor recoverywere significantly different for the two densities (2600 and 5200spat/collector bag) tested. Overall, these studies indicated that importantparameters for optimizing the growth and recovery of scallops in a farm-based nursery system include season, initial spat size, deployment depthand gear type.
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    Aquaculture international 8 (2000), S. 381-389 
    ISSN: 1573-143X
    Keywords: Arctic charr (Salvelinus alpinus) ; growth ; low temperature ; stocking density ; time restricted feeding,/kwd〉
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of time restricted feeding, possibility of bottomfeeding and stocking density on the growth of Arctic charr(Salvelinus alpinus L.) were examined in fish held at lowtemperature (〈2 °C). Fish fed for a restricted time (1 h) hadsignificantly (p 〈 0.05) lower specific growth rate (0.15 vs0.32% per day) than those fed the same ration over an extendedtime period (12 h). Increasing stocking densities had a positive andsignificant effect (p 〈 0.05) on growth with SGR increasing from 0.27to 0.52% per day at 2–30 kg m-3. Fish withaccess to feed on the tank floor had a significantly higher (p 〈0.05) growth rate (0.3 vs 0.13% per day) than those without thepossibility to feed from the bottom. When fish were held underconditions without access to the bottom a doubling of the feed rationdid not result in a significant (p 〉 0.05) increase in growth rate(0.13 vs 0.12%percnt; per day).
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    Journal of mammalian evolution 7 (2000), S. 1-22 
    ISSN: 1573-7055
    Keywords: Dasyurus ; marsupials ; control region ; mtDNA ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There has been a great deal of interest in determining phylogenetic relationships within the family Dasyuridae due to the widespread distribution, ecological diversity, and relative plesiomorphy of this taxon within the Australasian marsupial radiation. In the past, it has been extremely problematic to determine the phylogenetic relationships among species within Dasyurus, with numerous studies using both morphological and molecular characters providing different topologies. Here, the mitochondrial DNA (mtDNA) control region is used as a novel set of characters in an attempt to identify relationships among the six closely related extant species. Sequences were obtained from multiple individuals representing all extant species of quolls including, when possible, individuals from different geographical regions. Sequences were analyzed using both parsimony criteria and neighbor-joining methods. Results presented here concur with those of Krajewski et al. (1997) in (1) placing D. geoffroii in a highly supported clade with D. spartacus, (2) resolving a monophyletic group of D. albopunctatus + D. geoffroii + D. spartacus, and (3) placing D. hallucatus as the sister taxon to all other species of quolls. Results also show two highly supported and geographically distinct clades of D. maculatus (Tasmanian and mainland) that do not correspond to the currently used subspecific nomenclature. Preliminary results also indicate that there are different clades among geographic groups of D. hallucatus that warrant further investigation. The mtDNA control region is a highly variable locus and may be used in forensic tests for species identification in this genus.
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  • 84
    ISSN: 1573-6857
    Keywords: evolution ; Oryza ; retrotransposon ; rice ; wild species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Oryza officinalis complex is a genetically diverse, tertiary genepool of rice. We analyzed part of the primary structure of the integrase coding domain (ICD) of a gypsy-like retrotransposon from species of the O. officinalis species complex. PCR was performed with degenerate primers that hybridized to conserved sequences in the integrase genes of gypsy-type retrotransposons, using total DNA from different species of the O. officinalis complex as templates. Cloning and sequencing of the PCR products showed that the amplified fragments are highly homologous to each other (75–90%) and belong to one family of retrotransposons that is related to the previously studied RIRE-2 element from rice. Two main subfamilies of 292 and 351 bp were distinguished. Analysis of primary sequence data supports previous reports that sequence divergence during vertical transmission has been the major influence on the evolution of gypsy-type retrotransposons in Oryza species. Based on sequence data phylogenetic relationships among species of the O. officinalis complex were estimated. The data suggests that O. eichingeri is more closely related to the ancestral species of the complex.
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  • 85
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    International journal of primatology 21 (2000), S. 421-444 
    ISSN: 1573-8604
    Keywords: phylogenetics ; biogeography ; speciation ; Ateles ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used the results of phylogenetic analyses of relationships among spider monkeys (Ateles) based on mitochondrial and nuclear DNA to investigate questions of their evolutionary origins and speciation mechanisms. We employed the concept of a local molecular clock to date nodes of interest (corresponding to hypothesized species and subspecies) in the various phylograms for comparison to hypothesized biogeographical events that might have affected speciation. We considered various mechanisms—Pleistocene refuge formation, riverine barriers, geological fluctuations, and ecological changes associated with these mechanisms—for their contribution to speciation in Ateles. Most speciation among the various species of Ateles occurred during the middle to late Pliocene, suggesting that Pleistocene refuge formation was not a key speciation mechanism. However, it is likely that the genetic structure of populations of Ateles was modified to some extent by refuge formation. Additionally, riverine barriers do not seem to interrupt gene flow significantly among Ateles. No river formed a barrier among species of Ateles, with the exception of the lower Amazon and possibly some of the black-water rivers draining the Guianan highlands. Large-scale geographic changes associated with the continued rise of the eastern and western cordilleras of the northern Andes and associated changes in habitat were the most important causes of speciation in Ateles. The various factors that modify genetic structure in Ateles are important to consider in order to protect endangered primate genera in the Neotropics.
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  • 86
    ISSN: 1573-8604
    Keywords: vocalization ; sexual advertisement ; predator advertisement ; taxonomy ; evolution ; mouse lemur ; primate ; Madagascar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Advertisement calls are often important noninvasive tools for discriminating cryptic species and for assessing specific diversity and speciation patterns in nature. We investigated the contribution of these calls to uncover specific diversity in nocturnal Malagasy lemurs. We compared sexual advertisement and predator advertisement calls of two mouse lemur species, western gray and eastern rufous mouse lemurs (Microcebus murinus and M. rufus, respectively) living in two contrasting habitats (dry deciduous vs. rain forest), and analyzed them statistically. Both species emitted several highly variable whistle calls in the context of predator-avoidance. Intrapopulation variation was high and overlapped interspecific variation. Sexual advertisement calls, given in the mating context, displayed a totally distinct, species-specific acoustic structure. Whereas gray mouse lemurs produced rapidly multifrequency modulated, long trill calls, rufous mouse lemurs gave slowly frequency-modulated short chirp calls. Our results suggest specific status for gray and rufous mouse lemurs and indicate the importance of predation and social needs in shaping vocal communication.
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  • 87
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    Evolutionary ecology 14 (2000), S. 665-692 
    ISSN: 1573-8477
    Keywords: disease ; evolution ; frequency-dependent selection ; genetic diversity ; life history ; lifespan ; polymorphism ; reproduction rate ; resistance ; specificity ; virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pathogens and parasites can be strong agents of selection, and often exhibit some degree of genetic specificity for individual host strains. Here we show that this host–pathogen specificity can affect the evolution of host life history traits. All else equal, evolution should select for genes that increase individuals' reproduction rates or lifespans (and thus total reproduction per individual). Using a simple host–pathogen model, we show that when the genetic specificity of pathogen infection is low, host strains with higher reproduction rates or longer lifespans drive slower-reproducing or shorter-lived host strains to extinction, as one would expect. However, when pathogens exhibit specificity for host strains with different life history traits, the evolutionary advantages of these traits can be greatly diminished by pathogen-mediated selection. Given sufficient host–pathogen specificity, pathogen-mediated selection can maintain polymorphism in host traits that are correlated with pathogen resistance traits, despite large intrinsic fitness differences among host strains. These results have two important implications. First, selection on host life history traits will be weaker than expected, whenever host fitness is significantly affected by genotype-specific pathogen attack. Second, where polymorphism in host traits is maintained by pathogen-mediated selection, preserving the genetic diversity of host species may require preserving their pathogens as well.
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  • 88
    ISSN: 1615-6110
    Keywords: Cladistics ; evolution ; Illiciales ; Illicium ; ITS ; star anise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA were determined for 15 species ofIllicium (Illiciaceae) to examine phylogenetic relationships. The ITS trees show a major dichotomy between the two North American species (I. floridanum andI. parviflorum) and the remaining east Asian species. This suggests that the existing division between two sections (sect.Illicium and sect.Cymbostemon) ofIllicium based on tepal characters in unnatural. The ITS phylogeny shows congruence with palynology: of the species examined, the three species (I. angustisepalum, I. anisatum andI. fargesii) from sect.Illicium that possess trizonocolpate pollen consistently form a clade, although nesting within a clade consisting of the species of sect.Cymbostemon, which generally have trisyncolpate pollen. The low ITS sequence divergence and the close relationship among east Asian species suggest a recent diversification of this group of species or an unusual slowdown of sequence mutations.
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  • 89
    ISSN: 1615-6110
    Keywords: In situ hybridization ; evolution ; NOR ; rDNA ; Muscari
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it presents the most asymmetrical karyotype of the group and because its only active NOR is located in the fifth chromosome pair, while in the other species it is located in the first or second chromosome pairs (all the species have 2n = 18 chromosomes). SinceM. comosum has a derived karyotype different from those of the other species of the group, the resulting question is whether, in the first and second chromosome pair of this species, ribosomal cistrons persist. Observations after fluorescence in situ hybridization (FISH) using rDNA probes indicate that there are indeed ribosomal loci in the first and second chromosome pairs of this species, although these loci are inactive with respect to nucleolus organization. The location of rDNA regions in another three species of the same genus (M. atlanticum, M. dionysicum andM. matritensis) provides a basis for examining the significance of these findings in relation to the evolution of the ribosomal loci in this genus. Our observations indicate that in the genusMuscari, the largest sites for rRNA genes are not necessarily active, and, therefore, the activation of these regions is not related to the number of copies but to a specific regulation mechanism.
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  • 90
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    Journal of economics 71 (2000), S. 1-30 
    ISSN: 1617-7134
    Keywords: evolution ; local interaction ; cooperation ; prisoner's dilemma ; Markov processes ; C78
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We study local interaction within a population located on a connected graph. Subjects engage in several bilateral interactions during each round in a generalized Prisoners' Dilemma (PD). In each round of play one randomly selected player gets the possibility to update the action he plays in this PD. All individuals use the update rule “Win Cooperate, Lose Defect,” a multi-player variant of Tit-for-Tat. Theoretical results on the set of stable states of the associated dynamics are provided for the cases with and without rare mutations. Simulations provide insight into the probability distribution over these stable states. In both cases a rather high probability is assigned to stable states with a moderate level of cooperation implying that dominated strategies are used. Furthermore, the probability of reaching the stable state with Nash equilibrium play is small.
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  • 91
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    Annals of biomedical engineering 28 (2000), S. 128-134 
    ISSN: 1573-9686
    Keywords: Hippocampus ; Vigilance states ; Paired-pulse ; Dentate gyrus ; Dentate granule cells ; Evoked response ; Rat ; In vivo studies ; Perforant path ; Maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This study examined the effect of normal development and vigilance state on the modulation of dentate granule cell activity in the freely moving rat at 15, 30, and 90 days of age across three vigilance states: quiet waking, slow-wave sleep, and rapid eye movement sleep. Using paired-pulse stimulation, the paired-pulse index (PPI) was obtained for the dentate evoked field potentials elicited by the stimulation of the medial perforant path. Although significant differences in PPI values were observed during development, no significant vigilance state related changes were obtained. Preweaning infant rats, i.e., 15-day old, exhibited significantly less early (interpulse intervals, IPI= 20–50 ms) and late (IPI = 300–1000 ms) inhibition, and less facilitation (IPI = 50–150 ms) when compared to the 90-day old adult rats during all three vigilance states. PPI values obtained from the 30-day old group fell intermediate between the 15- and 90-day old animals. These changes in PPI values provide a quantitative measure of changes in the modulation of dentate granule cell excitability during normal maturation. They can now can be used to evaluate the impact of various insults, such as prenatal protein malnutrition or neonatal stress, on hippocampal development. © 2000 Biomedical Engineering Society. PAC00: 8717Nn, 8719La, 8719Nn
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  • 92
    ISSN: 1573-9686
    Keywords: Heart ; Left ventricle ; LV contractility ; ESPVR ; Pig ; Rat ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The end systolic pressure–volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR $$\left( {E_{es} } \right)$$ decreased significantly following infarction in both species, while the volume-axis intercept $$\left( {V_0 } \right)$$ was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8761Lh, 8719Hh, 8719Rr, 8719Ff
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  • 93
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    Annals of biomedical engineering 28 (2000), S. 1101-1115 
    ISSN: 1573-9686
    Keywords: Time–frequency analysis ; Coherence ; Cross correlation ; Nonstationary persistent signals ; Central pattern generator ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We present a novel time-varying phase spectrum (TVPS) method to quantify the dynamics of coevolution of two persistent nonstationary coupled signals. Based on the TVPS, an instantaneous intersignal phase shift is defined within the primary frequency range in which the two signals are highly correlated. The TVPS is estimated using a fixed-window method or an adaptive-window method. In the latter method, the window length changes dynamically and automatically as a function of change in frequency of the signals. The effects of altering window types and lengths on the accuracy of the estimation of the primary phase shift is assessed by analyzing synthesized linear chirp signals with decaying amplitude and constant relative phase shift or decaying amplitude and changing relative phase shifts. The methods developed are also used for determining the evolution of the primary phase shift among ventral root activities during fictive locomotion in an in vitro rat spinal cord preparation. The analyses indicate that the TVPS method in conjunction with the determination of the primary frequency range, allows determination of both the evolution of the coupling strength and the evolution of the phase shift between two persistent nonstationary rhythmic signals in the joint time–frequency domain. An adaptive window reduces the estimation bias and the estimation variability. © 2000 Biomedical Engineering Society. PAC00: 0230-f, 8780Tq
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  • 94
    ISSN: 1573-5028
    Keywords: evolution ; C4 plant ; maize ; ribulose-bisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The small subunit of ribulose-bisphosphate carboxylase (Rubisco), encoded by rbcS, is essential for photosynthesis in both C3 and C4 plants, even though the cell specificity of rbcS expression is different between C3 and C4 plants. The C3 rbcS is specifically expressed in mesophyll cells, while the C4 rbcS is expressed in bundle sheath cells, and not mesophyll cells. Two chimeric genes were constructed consisting of the structural gene encoding β-glucuronidase (GUS) controlled by the two promoters from maize (C4) and rice (C3) rbcS genes. These constructs were introduced into a C4 plant, maize. Both chimeric genes were specifically expressed in photosynthetic organs, such as leaf blade, but not in non-photosynthetic organs. The expressions of the genes were also regulated by light. However, the rice promoter drove the GUS activity mainly in mesophyll cells and relatively low in bundle sheath cells, while the maize rbcS promoter induced the activity specifically in bundle sheath cells. These results suggest that the rice promoter contains some cis-acting elements responding in an organ-pecific and light-inducible regulation manner in maize but does not contain element(s) for bundle sheath cell-specific expression, while the maize promoter does contain such element(s). Based on this result, we discuss the similarities and differences between the rice (C3) and maize (C4) rbcS promoter in terms of the evolution of the C4 photosynthetic gene.
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  • 95
    ISSN: 1573-5036
    Keywords: growth ; inflow ; magnesium ; potassium ; (Prunus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects (and interaction) of two solution concentrations of Mg (50, 500, μM) and two of K (250, 4250 μM) on the growth of micropropagated plants of “F. 12/1” and “Colt” were investigated using a flowing solution culture system. Magnesium inflow and growth of “Colt” and “F. 12/1” were inhibited to a similar extent by an increased concentration of K in the nutrient solution. However, the consequences of this inhibition were different. Reduced inflow of Mg in “F. 12/1” caused Mg deficiency symptoms at high and low concentrations of K, whereas this only occurred with a combination of high K concentration and low Mg concentration in “Colt”. The distribution of dry matter within the plant was significant in determining susceptibility to Mg deficiency. Since “F. 12/1” has a smaller root:shoot ratio than Colt it is unable to sustain the same concentration of Mg in leaves as “Colt” irrespective of external K concentration. The molar ratio of K:Mg in soil solutions should remain 〈8.5:1 in order to ensure maximum growth of “F. 12/1” and “Colt”.
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  • 96
    ISSN: 1573-5036
    Keywords: evolution ; glutamine synthetase ; sequences ; subunit composition ; Trientalis europaea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ion-exchange chromatography of extracts from Trientalis europaea L. leaf tissue have been shown to contain two distinct isoforms of glutamine synthetase (GS). However, analysis by Western blotting has shown that the first peak to elute contains a mixture of large and small GS subunits, whilst the second peak is comprised entirely of a smaller subunit. This is contrary to the widespread assumptions concerning plant GS biochemistry. Isolation of intact chloroplasts and subsequent extraction of GS, followed by ion-exchange chromatography, has shown that the first peak to elute contains a large subunit, and the second chloroplastic peak is composed entirely of the small subunit. This smaller subunit may be present due to it being encoded by a separate chloroplastic GS gene, or it may be present as a product of post-translational modification. DNA sequencing has been used to try and determine which of these may be occurring. The three partial DNA sequences (505 nucleotides) we have obtained from T. europaea have been compared with 64 other sequences available on the NCBI database, which have mainly been obtained from crop species. Neighbour joining and parsimony analysis (1000 bootstrap) has shown support (∼30%) for the separation of plant GS from all other phyla. Within the plant phylum, there is total support for the separation of chloroplastic and cytosolic GS (100%), whilst the cytosolic sequences divide further into monocot and dicot species (77% support by NJ). Further subgroups of plants from the same families is also suggested. This is consistent with previous work containing fewer, but longer (∼1000 nucleotides) GS sequences. The addition of GS sequences obtained from wild plant species, such as T. europaea, to the large amount of information already available on the database, will permit a better understanding of the evolution of this important enzyme.
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  • 97
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    Plant and soil 219 (2000), S. 177-185 
    ISSN: 1573-5036
    Keywords: alfalfa ; growth ; Medicago sativa L. ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dynamics of biomass and N accumulation following defoliation of alfalfa and the application of N fertilization has rarely been studied under field conditions, particularly in the seeding year. Our objectives were to determine the effect of N fertilization on the dynamics of biomass and N accumulation during the first regrowth of alfalfa in the seeding year, and to determine if a model describing critical N concentration developed for established stands could be used in the seeding year. In two separate experiments conducted in 1992 and 1993, the biomass and N accumulation of alfalfa grown with three N rates (0, 40 and 80 kg N ha-1) were determined weekly. Maximum shoot growth was reached with 40 kg N ha-1 in 1992, and maximum shoot growth was not reached with the highest N fertilization rate in 1993. Nitrogen fixation, root N reserves and soil inorganic N uptake when no N was applied were, therefore, not sufficient to ensure non-limiting N conditions, particularly when growth rates were the highest between 14 to 21 d after defoliation. Nitrogen fertilization increased shoot biomass accumulation in the first 21 d of regrowth, biomass partitioning to the shoots and shoot and taproot N concentrations. The model parameters of critical N concentration developed by Lemaire et al. (1985) for established stands of alfalfa were not adequate in the seeding year. The N requirements per unit of shoot biomass produced are greater in the seeding year than on established stands, and this was attributed to a greater proportion of leaves in the seeding year.
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  • 98
    ISSN: 1573-5036
    Keywords: growth ; light intensity ; Phaseolus vulgaris L. ; phosphorus–zinc interaction ; photosynthesis ; yield ; zinc deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two experiments were conducted in a factorial combination of three Zn levels (0, 10 and 40 mg Zn kg-1 soil) and two P levels (0 and 200 mg P kg-1 soil). Experiment 1 was carried out during winter in a heated glasshouse, and experiment 2 during summer under a rain shelter. Plants of dwarf bean (Phaseolus vulgaris L., cv. Borlotto nano) were grown in pots filled with sandy soil. In both experiments, leaf Zn concentration was reduced by the addition of P to plants grown at low Zn supply. However, leaf Zn concentration lower than the critical level was observed only during experiment 2, and the main effects of low Zn were reductions of internode length, light use efficiency and maximum photosynthetic rate. In plants with leaf Zn concentration lower than the critical level, saturating irradiance levels fell from ∼1000 μmol m-2 s-1 PPFD to ∼300–400 μmol m-2 s-1 PPFD. Reduction of net photosynthesis was observed from the beginning of flowering and led to decreased seed production.
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  • 99
    ISSN: 1573-5036
    Keywords: AM fungi ; colonisation ; growth ; mineral nutrition ; red raspberry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth, development and nutrient status of micropropagated Rubus idaeus cv. Glen Prosen in response to inoculation with nine species of arbuscular mycorrhizal (AM) fungi from three different genera was investigated. The nine species of AM fungi included, Glomus clarum, G. etunicatum, G. intraradices, Gigaspora rosea, Gi. gigantea, Gi. margarita, Scutellospora calospora, S. heterogama and S. persica. Plant responses to AM fungi varied from growth enhancement to growth depression. Depressive growth effects were specific to Gigaspora species. Furthermore, particular species of AM fungi had unique effects on the mineral status of the raspberry plants. Importance of isolate selection for inoculation of micropropagated raspberry plants is discussed.
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  • 100
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    Plant growth regulation 32 (2000), S. 77-81 
    ISSN: 1573-5087
    Keywords: bioenergetics ; growth ; nutrition ; nutrient deficiency ; plant stress ; respiration ; root ; root:shoot ratio ; root respiration ; source-sink relationship ; stress ; stress physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root respiration of kohlrabi (Brassica oleraceavar. gongylodes) was measured non-destructivelyin vivo by infrared gas analysis of completeroot systems, using potted plants in sand culture andnutrient solutions, for six weeks under (a) nutrientsufficiency, (b) deficiency of all mineral nutrients,(c) potassium deficiency or (d) phosphorus deficiency.This was to study the adaptation to nutrient stress interms of changes in root growth, root respiration,assimilate allocation and energy requirement fornutrient uptake. Both deficiencies of phosphorus andpotassium increased the root:shoot-ratio. This wasattributed to the plants transferring a largerrelative proportion of assimilates to the roots thanto the shoots relative to nutrient-sufficient plants.Roots of nutrient-sufficient kohlrabi respired 1.7 or7.7 mg CO2 h−1 per g fresh or dry matter, respectively. However, potassiumdeficiency enhanced root respiration to 2.4 mgCO2 h−1 or 12.2 mg CO2 h−1 on a per g fresh or dry weight basis respectively. This originated from an additional2.6 mg glucose g−1 dry matter h−1 allocated to the roots and provided 50 Joule additional energy(150 versus 100 Joule g−1 dry matter h−1)which may become available for the proposedK+:H+ symporter for potassium uptake.
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