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  • 1
    Electronic Resource
    Electronic Resource
    Molecular systematics of vestimentiferan tubeworms from hydrothermal vents and cold-water seeps (1997)
    Springer
    Marine biology 130 (1997), S. 141-149 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vestimentiferan tubeworms inhabit sulfide-rich environments associated with deep-sea hydrothermal vents and cold-water seeps at continental margins. Twelve species have been described, and several more await formal descriptions. As a group, these worms are best known for their lack of a digestive system in adults and their dependence on endosymbiotic bacteria that supply nutrients derived from chemoautotrophism. The taxonomic status of Vestimentifera has been debated since their discovery. Furthermore, relationships within the Vestimentifera have been difficult to determine by morphological criteria. Several species display considerable phenotypic plasticity, further confounding efforts to establish evolutionary relationships. We used a fragment of the mitochondrial cytochrome c oxidase subunit I gene to examine evolutionary relationships among vent-endemic species (Riftia pachyptila, Oasisia alvinae, Ridgeia piscesae, Tevnia jerichonana) and seep-associated species(Escarpia laminata, E. spicata, Lamellibrachia barhami, L. columna, and an undescribed species) of these worms. The molecular data placed these vestimentiferan taxa within the phylum Pogonophora. The pogonophoran clade (including vestimentiferans) was then linked to the Annelida. Examination of sequence divergence suggests that extant vestimentiferans constitute a recent evolutionary radiation that diversified as a paraphyletic assemblage of seep-associated taxa (including the genera Lamellibrachia and Escarpia) and then gave rise to a clade of vent-endemic taxa (genera Riftia, Oasisia, Ridgeia and Tevnia).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050233
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  • 2
    Electronic Resource
    Electronic Resource
    Evolutionary relationships of deep-sea hydrothermal vent and cold-water seep clams (Bivalvia: Vesicomyidae): results from the mitochondrial cytochrome oxidase subunit I (1997)
    Springer
    Marine biology 130 (1997), S. 151-161 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phylogenetic relationships among vesicomyid clams (Bivalvia: Vesicomyidae) and their placement within the order Heterodonta were examined using mitochondrial encoded cytochrome oxidase subunit I (COI) DNA sequences. The presently analyzed vesicomyids represent a recent monophyletic radiation that probably occurred within the Cenozoic. Nucleotide phylogenetic analyses resolved discrete clades that were consistent with currently recognized species: Calyptogena magnifica, C. ponderosa, Ectenagena extenta, C. phaseoliformis, Vesicomya cordata, Calyptogena n. sp. (Gulf of Mexico), C. kaikoi, C. nautilei, C. solidissima and C. soyoae (Type-A). However, specimens variously identified as: V. gigas, C. kilmeri, C. pacifica, and V. lepta comprised two “species complexes”, each composed of multiple evolutionary lineages. Most taxa are limited to hydrothermal-vent or cold-seep habitats, but the “vent” versus “seep” clams do not constitute separate monophyletic groups. Current applications of the generic names Calyptogena, Ectenagena, and Vesicomya are not consistent with phylogenetic inferences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050234
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic differentiation between spatially-disjunct populations of the deep-sea, hydrothermal vent-endemic amphipod Ventiella sulfuris (1992)
    Springer
    Marine biology 114 (1992), S. 551-559 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Species endemic to deep-sea hydrothermal vent ecosystems have disjunct distributions imposed by the island-like arrangement of their specialized habitats. Using allozyme electrophoresis, we examined genetic population structure of the hydrothermal vent amphipod Ventiella sulfuris Barnard and Ingram, 1990. Samples from five sites along the East Pacific Rise (EPR) and two along the Galapagos Rift were collected in 1990 and 1988, respectively. Variability, based on 12 enzyme loci, was relatively high $$\bar P$$ (proportion of polymorphic loci whose most common allele not greater than 0.95 in frequency) =41.6%; $$\bar H$$ (mean heterozygosity) =0.158] compared with shallow-water marine and freshwater amphipods, and similar to the deep-sea lysianassid Eurythenes gryllus. Genetic divergence among populations spread along a cöntiguous rift axis (i.e., EPR) was low [Nei's genetic distance (D) ranged from 〈0.001 to 0.018]. Genetic tructure analysis suggests that along a contiguous ridge axis migration occurs in a stepping stone manner and is unconstrained by distances as great as 1200 km (migration rate, $$\bar M$$ , ranged from 1.9 to 67.8 ind. generation−1). However, genetic divergence between populations on disjunct ridge axes was extremely high (D ranged from 0.438 to 0.476). Most of the variance in gene frequencies was due to the differences between the major subpopulations inhabiting the two distinct ridge axes, EPR and Galapagos Rift. Apparently, very little migration and gene flow occur between these major subpopulations (M≪1). This level of genetic divergence may be sufficient to justity separation of EPR and Galapagos Rift populations at the species level. Futher analyses of morphological characters is required before taxonomic status can be assigned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357252
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  • 4
    Electronic Resource
    Electronic Resource
    Heterozygosity, growth, and survival of the hard clam,Mercenaria mercenaria, in seagrass vs sandflat habitats (1991)
    Springer
    Marine biology 111 (1991), S. 335-342 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Populations of the hard clam,Mercenaria mercenaria L., sampled from dissimilar, adjacent habitats (October and November 1987), were used to assess environmental effects on associations among multi-locus heterozygosity, growth, and survival. Individuals were collected from three widely separated localities along the east coast of North America with each consisting of a seagrass bed and an adjacent, unvegetated sandflat. Demographic differences between adjacent populations were attributed to habitat type. Samples from intertidal sandflats at two of the localities were dominated by younger individuals than those from seagrass beds. Differential growth between adjacent populations was detected at only one locality wherein seagrass individuals grew faster than those from the sandflat. Allelic frequencies revealed adjacent populations that were genetically homogeneous. Nearly all of the genetic variance (98%) was within populations, yet a small (1.7%), but significant, portion occurred between localities. Observed and expected heterozygosities revealed a deficiency of heterozygotes in all six samples. Inbreeding and small-scale population subdivision were discounted as causative factors because deficiencies were heterogeneous across loci. Multi-locus heterozygosity was not correlated with growth rate in samples from any locality. Using a consensus test, multilocus heterozygosity was positively associated with ageclass in sandflat, but not seagrass, samples. We suggest that heterozygosity-fitness trait associations in marine bivalves are more likely to occur in populations inhabiting more stressful, fluctuating environments
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01319404
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  • 5
    Electronic Resource
    Electronic Resource
    Extensive gene flow among mytilid (Bathymodiolus thermophilus) populations from hydrothermal vents of the eastern Pacific (1995)
    Springer
    Marine biology 124 (1995), S. 137-146 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Prior studies of the hydrothermal vent mussel Bathymodiolus thermophilus (Bivalvia: Mytilidae), provided conflicting predictions about the dispersal ability and population structure of this highly specialized species. Analyses of morphological features associated with its larval shells revealed a feeding larval stage that might facilitate dispersal between ephemeral vent habitats. In contrast, an allozyme study revealed substantial genetic differentiation between samples taken from populations 2370 km apart on Galápagos Rift (Latitude 0°N) and the East Pacific Rise (13°N). To resolve the discrepancy between these studies, we examined allozyme and mitochondrial (mt) DNA variation in new samples from the same localities plus more recently discovered sites (9° and 11°N) along the East Pacific Rise. Although analysis of 26 enzyme-determining loci revealed relatively low levels of genetic variation within the five populations, no evidence existed for significant barriers to dispersal among populations. We estimated an average effective rate of gege flow (Nm) of ≃ 8 migrants per population per generation. Two common mtDNA variants predominated at relatively even frequencies in each population, and similarly provided no evidence for barriers to gene flow or isolation-by-distance across this species' known range. Larvae of this species appear to be capable of dispersing hundreds of kilometers along a continuous ridge system and across gaps separating non-contiguous spreading centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349155
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  • 6
    Electronic Resource
    Electronic Resource
    Gene flow among vestimentiferan tube worm (Riftia pachyptila) populations from hydrothermal vents of the eastern Pacific (1994)
    Springer
    Marine biology 120 (1994), S. 33-39 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Allozyme data are presented for six discrete populations of the giant hydrothermal vent tube worm Riftia pachyptila Jones, 1981 collected throughout the species' known range along mid-ocean spreading ridges of the eastern Pacific Ocean. Contrary to an earlier report, levels of genetic variation are relatively high in this species. Estimates of gene flow based on F-statistics revealed that dispersal throughout the surveyed region is sufficiently high to counter random processes that would lead to losses of genetic diversity and significant population differentiation. R. pachyptila, like other species of tube worms, displays considerable morphologic variation among populations, but this diversity is not reflected in allozyme variation. Vestimentifera, in general, appear to show extensive phenotypic plasticity. In the light of the available genetic data, caution is warranted when making inferences about the taxonomic status of collections based on morphological variation alone. A general decrease in estimated rates of gene flow between geographically more distant populations supports the hypothesis that dispersal in this species follows a stepping-stone model, with exchange between neighboring populations in great excess of long-distance dispersal. High levels of gene flow have been recorded in a variety of vent fauna and may be a prerequisite for success of species found in the ephemeral habitats associated with regions of sea-floor hydrothermal activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381939
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  • 7
    Electronic Resource
    Electronic Resource
    Unisexual Fish: Model Systems for Studying Ecology and Evolution (1994)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 25 (1994), S. 71-96 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.es.25.110194.000443
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  • 8
    Electronic Resource
    Electronic Resource
    Conservation genetics of freshwater fish (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 53 (1998), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Genetic markers have helped to resolve many difficult taxonomic problems and map patterns of diversity within and among remnant populations of threatened and endangered species. Knowledge of historical patterns of gene flow can help to manage dispersal among anthropogenically fragmented populations. Genetic considerations are used in the design of captive breeding programmes that avoid inbreeding depression and artificial selection that may impact on Darwinian fitness. Case studies from endangered populations of topminnows from North American deserts are used to illustrate a variety of methods used in conservation genetic studies. Several merits of studying putatively neutral, molecular markers v. adaptive phenotypic traits are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1998.tb01039.x
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  • 9
    Electronic Resource
    Electronic Resource
    Genetic variability associated with hovering time inTabanus nigrovittatus Macquart (Diptera: Tabanidae) (1990)
    Springer
    Journal of insect behavior 3 (1990), S. 579-587 
    Details
    ISSN: 1572-8889
    Keywords: Genetics ; polymorphism ; reproductive isolation ; hovering behavior ; Tabanus nigrovittatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The salt marsh horse fly, Tabanus nigrovittatusMacquart, exhibits two nonoverlapping daily periods of hovering and mating activity, which are correlated with different environmental temperatures. Allelic and genotypic frequencies of hovering males collected during the two periods were compared by electrophoresis of three polymorphic enzyme loci. Approximately 26% of early-hovering males possessed a Pgmallozyme that was absent in our sample of late-hovering males. However, based on other allozyme loci, we found no evidence for reproductive isolation between early and late hoverers. All the genetic data are consistent with the hypothesis that the Pgmpolymorphism is associated with behaviorally and physiologically distinct groups of males that, by all other criteria, form a single Mendelian population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052329
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  • 10
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    Unknown
    An ancient clonal lineage in the fish genus Poeciliopsis (Atheriniformes: Poeciliidae). (1992)
    National Academy of Sciences
    Details
    Publication Date: 1992-01-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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