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  • Springer  (42)
  • American Meteorological Society  (8)
  • Wiley-Blackwell
  • 1990-1994  (37)
  • 1980-1984  (9)
  • 1970-1974  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    A neural network for processing olfactory-like stimuli (1991)
    Springer
    Bulletin of mathematical biology 53 (1991), S. 805-823 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Several critical issues associated with the processing of olfactory stimuli in animals (but focusing on insects) are discussed with a view to designing a neural network which can process olfactory stimuli. This leads to the construction of a neural network that can learn and identify the quality (direction cosines) of an input vector or extract information from a sequence of correlated input vectors, where the latter corresponds to sampling a time varying olfactory stimulus (or other generically similar pattern recognition problems). The network is constructed around a discrete time content-addressable memory (CAM) module which basically satisfies the Hopfield equations with the addition of a unit time delay feedback. This modification improves the convergence properties of the network and is used to control a switch which activates the learning or template formation process when the input is “unknown”. The network dynamics are embedded within a sniff cycle which includes a larger time delay (i.e. an integert s 〈1) that is also used to control the template formation switch. In addition, this time delay is used to modify the input into the CAM module so that the more dominant of two mingling odors or an odor increasing against a background of odors is more readily identified. The performance of the network is evaluated using Monte Carlo simulations and numerical results are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461485
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  • 2
    Electronic Resource
    Electronic Resource
    Sex ratio genetics and the competitiveness of parasitic wasps (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 295-311 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In the first part of the paper we analyse dynamics of the genetic mechanisms responsible for maintaining biased sex ratios in host-parasitoid interactions. We begin by reviewing recent results relating to the maintenance of sibmating in haplo-diploid populations. We then investigate the evolutionary stable sex ratio in populations in which all or some of the females mate with their brothers. In particular, we derive a diallelic one-locus model for studying evolutionary stable sex ratios in partially sibmating haplo-diploid populations. In the second part of the paper we review the impact of sex ratio on host-parasitoid populations. We then analyse how the sex ratio strategy of one parasitoid species may affect its interaction with another parasitoid species competing for the same host. In particular we show that, although a female biased sex ratio may enhance the inherent competitiveness of one species, it may also destabilize the ecological interaction of the three species so that all become extinct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464835
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of seed size on seedling size in Virola surinamensis; a within and between tree analysis (1982)
    Springer
    Oecologia 53 (1982), S. 347-351 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We conducted a greenhouse study of the effects of initial seed mass on seedling characteristics in a Panamanian population of Virola surinamensis, a canopy tree in which mean seed mass of different individuals ranges from 1.34 to 4.04g. The system is of particular interest because birds preferentially eat fruits of small-seeded plants, leaving seedlings of large-seeded individuals under conditions of potentially severe sibling competition (Howe and Vande Kerckhove 1980). Effects of differences of mean seed mass between trees are explored using an analysis of variance, while effects of seed-mass variation within crops are demonstrated with a regression analysis. A two-way analysis of variance decisively shows effects of parental source and light condition on seedling height, leaf length, and dry shoot mass (all P〈0.0001). A posteriori tests show that differences in seedling characteristics reflect differences in initial seed mass, with especially strong differences apparent in shoot mass. Regression of seedling characteristics on initial seed mass shows that variation of seed size within a crop is sufficient to influence shoot mass at 15 weeks (P〈0.0001). Effects of size differences of seeds that land adjacent to each other, either under the parent or in monkey droppings, are documented with growth of pairs of seedlings in pots. Differences in shoot height and mass at 15 weeks are evident when seeds of average size differ by only 0.2 g, and dramatic differences are evident when paired seeds differ by an average of 1.5 g. Seedlings grow more when isolated than when planted with conspecifics. These experimental results offer indirect support for the hypothesis that small-seeded Virola parents secure an advantage in reproduction through differential dispersal, while large-seeded plants produce more competitive seedlings under their own crowns — an advantage most likely to be of importance when frugivores are scarce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389011
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  • 4
    Electronic Resource
    Electronic Resource
    The occurrence of microbodies and peroxisomal enzymes in achlorophyllous leaves (1972)
    Springer
    Planta 105 (1972), S. 114-138 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several types of leaves of leaf parts lacking chlorophyll were fixed and embedded according to conventional procedures and examined electron-microscopically for microbodies. Comparisons of relative abundance of microbodies, plastids and mitochondria were made by computing the average numbers of organelle profiles per cell section. Similar leaves were homogenized and assayed for three enzymes characteristic of leaf peroxisomes. The localization of these enzymes in microbodies was indicated for the achlorophyllous tissues by the positive result obtained when 3,3′-diaminobenzidine was used as an electron cytochemical stain for catalase activity. Microbodies were present in all non-photosynthetic leaves or leaf parts examined, including yellowish-white segments of variegated leaves, albino leaves, and etiolated leaves of two species. In several cases, the numbers of microbody profiles per cell section were as great in the achlorophyllous leaves as in the chlorophyllous. The levels of peroxisomal enzyme activity in the yellowish-white leaves were substantial, although often not as high as in the green leaves. It was concluded that enzymatically these microbodies are probably similar to the peroxisomes characterized from chlorophyllous leaves. In the absence of the photosynthetic product, glycolate, however, it seems unlikely that the organelle is performing the same functions as in green leaves. It is also apparent that the initial formation of peroxisomes in leaves can occur when neither light nor a photosynthate such as glycolate is present as an inducer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385572
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  • 5
    Electronic Resource
    Electronic Resource
    Olfactory perception in honeybees: Concatenated and mixed odorant stimuli, concentration, and exposure effects (1991)
    Springer
    Journal of comparative physiology 169 (1991), S. 215-230 
    Details
    ISSN: 1432-1351
    Keywords: Differential conditioning ; Proboscis extension reflex ; Learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Here we present results obtained from 7 different series of experiments, all employing odor conditioning of proboscis extension in worker honeybees and each designed to address a particular question involving olfactory perception. The questions relate to: temporal complexity of odor cues; effects of concentration, suppression, and/or potentiation in mixture perception; acquisition and extinction rates, as well as levels of generalization associated with aliphatic compounds that have the same functional groups or same alkyl radical length; and the effects of continuous exposure to odorants in the first several days of adult life on various learning and discrimination tasks involving olfactory perception. From the data obtained in these experiments we were able to conclude the following: First, worker honeybees have a limited ability to perceive complex temporal odor-quality patterns in olfactory stimuli — they learn to associate the quality of only the last part of the stimulus with a sucrose reward. Second, we confirm that citral is qualitatively different in several perceptual contexts involving odor learning and conditioning and our results help elucidate the nature of these differences as they relate to learning, discrimination, mixture perception, and continuous exposure to particular odorants. Third, we appear to have uncovered some important perceptual differences between functional groups attached to the first as opposed to the second carbon atom of alkyl radicals. Finally, we failed to uncover any significant effects relating to continuous exposure to odorants during the first several days of a worker's adult life, despite evidence that considerable sensory development takes place during this period. Thus ontogenetic changes to the peripheral system due to environmental effects appear to leave basic perceptual systems unaltered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215869
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of genes encoding hydroxypyruvate reductase in cucumber (1991)
    Springer
    Plant molecular biology 17 (1991), S. 941-947 
    Details
    ISSN: 1573-5028
    Keywords: hydroxypyruvate reductase ; light regulation ; peroxisomal enzymes ; photorespiration ; plant gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several clones corresponding to the gene encoding NADH-dependent hydroxypyruvate reductase have been isolated from a cucumber genomic library. Restriction mapping indicates the presence of two HPR genes, hpr-A and hpr-B, in the cucumber genome. Examination of the DNAs of individual plants suggests that hpr-A and hpr-B are most likely alleles at a single locus. The sequence of a 6.7 kb genomic fragment that includes the entire transcribed region, 2.2 kb of 5′ flanking sequence, and about 0.8 kb of 3′ flanking sequence reveals the presence of 12 introns in hpr-A. These introns are AT-rich relative to the exons. The donor sequence at the 5′ end of the sixth intron contains an unusual dinucleotide, GC, rather than the nearly invariant GT. Primer extension analysis maps the transcription initiation site to 61 nucleotides upstream of the translation initiation codon. An AT-rich stretch is centered at position −31 with respect to the transcription initiation site, and a potential CCAAT box is centered at position −138. Several elements that are homologous to regulatory elements of other plant genes have been identified in the flanking regions of hpr-A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00037078
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  • 7
    Electronic Resource
    Electronic Resource
    A correlative ultrastructural and enzymatic study of cotyledonary microbodies following germination of fat-storing seeds (1970)
    Springer
    Planta 93 (1970), S. 269-288 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sunflower, cucumber, and tomato cotyledons, which contain microbodies in both the early lipid-degrading and the later photosynthetic stages of post-germinative growth, were processed for electron microscopy according to conventional procedures and examined 1, 4 and 7 days after germination. Homogenates of sunflower cotyledons were assayed for enzymes characteristic of glyoxysomes and leaf peroxisomes (both of which are defined morphologically as microbodies) at stages corresponding to the fixations for electron microscopy. The particulate nature of these enzymes was demonstrated by differential and equilibrium density centrifugation, making it possible to relate them to the microbodies seen in situ. One day after germination, the microbodies are present as small organelles among large numbers of protein and lipid storage bodies; the cell homogenate contains catalase but no detectable isocitrate lyase (characteristic of glyoxysomes) or glycolic acid oxidase (characteristic of leaf peroxisomes). 4 days after germination, numerous microbodies (glyoxysomes) are in extensive and frequent contact with lipid bodies. The microbodies often have cytoplasmic invaginations. At this stage the cells are rapidly converting lipids to carbohydrates, and the homogenate has high isocitrate lyase activity. 7 days after germination, microbodies (peroxisomes) are appressed to chloroplasts and frequently squeezed between them in the green photosynthetic cells. The homogenate at this stage has substantial glycolic acid oxidase activity but a reduced level of isocitrate lyase. It is yet to be determined whether the peroxisomes present at day 7 are derived from preexisting glyoxysomes or arise as a separate population of organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384101
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  • 8
    Electronic Resource
    Electronic Resource
    Kin structure and the swarming behavior of the honey bee Apis mellifera (1982)
    Springer
    Behavioral ecology and sociobiology 10 (1982), S. 265-270 
    Details
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experimental hives obtained from cordovan queens that were instrumentally inseminated with semen from one cordovan and one Italian drone were set up and allowed to swarm. Cordovan provides a resessive genetic marker system (cuticle color) so that the workers from the cordovan and Italian male lines are distinguishable. Our results show that these patrilineal worker groups segregate non-randomly during colony fission and this segregation cannot be explained by observed age structure. Evidence of innate kin recognition in bees has been previously established. We argue that kin recognition could be responsible for the observed non-random grouping of kin during swarming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302815
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  • 9
    Electronic Resource
    Electronic Resource
    Invasion of sibmating genes in diploid and haplodiploid populations (1992)
    Springer
    Evolutionary ecology 6 (1992), S. 312-330 
    Details
    ISSN: 1573-8477
    Keywords: genetic models ; inbreeding depression ; mating cost ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Existing genetic models of the evolution of sibmating behaviour in diploids incorporate inbreeding depression in terms of reduced fecundity of consanguineous mating pairs rather than reduced survival or fecundity of the progeny of such matings. Here we derive a model to correct this deficiency and extend the model to haplodiploids where differential effects of inbreeding in males and females is a crucial consideration. Our analyses indicate that sibmating can readily evolve in both diploids and haplodiploids in which male mating costs and inbreeding depression are reasonably low, provided there is some mechanism to permit sibmating such as siblings being reared in nests or other forms of aggregation. Our analyses also indicate that once sibmating invades, it typically will go to fixation, although sib-/randommating polymorphisms can persist in both diploids and haplodiploids if male mating costs are close to zero and inbreeding depression reduces survival by around one-third. The conditions favouring sibmating are slightly more restrictive in haplodiploids than in diploids. In light of this we may ask why we see intense sibmating in many haplodiploids such as parasitic wasps, fig wasps, ants, bark beetles and mites, and only rarely in diploid animals. The common factor could be certain kinds of aggregation behaviour that are a prerequisite for sibmating in the absence of kin recognition. Another possibility is that inbreeding depression is likely to be more severe in diploids than in haplodiploids because deleterious recessives are purged from haplodiploid populations when expressed by haploid males. Thus, lower levels of inbreeding depression might be one important reason why sibmating appears to arise more frequently in haplodiploids than diploids. Phylogenetic analysis of groups, such as bark beetles and mites, exhibiting both diploid and haplodiploid populations may be useful in elucidating the relative importance of gregarious behaviour and haplodiploidy in facilitating sibmating systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02270968
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  • 10
    Electronic Resource
    Electronic Resource
    An inclusive fitness model for the evolutionary advantage of sibmating (1994)
    Springer
    Evolutionary ecology 8 (1994), S. 61-69 
    Details
    ISSN: 1573-8477
    Keywords: sibmating ; inbreeding depression ; haplodiploid ; inclusive fitness ; one-locus genetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We construct an inclusive fitness model of the relative selective advantage of sibmating and outbreeding behaviour, under the assumption that inbred offspring pay a fitness penalty. We are particularly interested in the question of whether such inbreeding depression is enough to generate a stable phenotypic polymorphism, with both kinds of breeding observed. The model predicts that, under diploidy, such a polymorphism is never found, but under haplodiploidy, it exists for a narrow range of parameter values. The inclusive fitness argument is technically interesting because care must be taken with reproductive values. We also present a corrected version of a one-locus genetic model for sibmating and find that the inclusive fitness and genetic models give identical results when selection is weak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01237666
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