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| Population genetics of bathyal and abyssal organisms |  |
| Creasy, S.S.; Rogers, A.D. (1999). Population genetics of bathyal and abyssal organisms Adv. Mar. Biol. 35: 1-151 |
| In: Advances in Marine Biology. Academic Press: New York. ISSN 0065-2881, meer |
| Abstract |
Bathyal and abyssal environments are characterized by relatively stable physical parameters. Exceptions are found within hydrothermal vent fields, seeps and oxygen-minimum zones, where there is evidence for environmentally mediated selection at enzyme loci. Adaptations to conditions of low oxygen and high toxin concentrations have occurred in a number of organisms. Deep-sea population genetics is known mostly from biochemical data. From these data, the relationship between heterozygosity and polymsrphic loci does not reveal any significant difference from neutral theory expectations. Comparisons behveen deep-sea vertebrates, invertebrates and vent-endemic species show some significant differences in observed heterozygosity. These may be explained by low sample sizes and taxonomic bias within different categories. No significant correlation was found between bathyme?trie distribution and heterozygosity. Analyses of correlations between life history characteristics and genetic variation are difficult because of low sample sizes, taxonomic bias and lack of methodological consistency. Levels of genetic identity between conspecific, congeneric and confamilial populations are broadly similar in deep-sea organisms and those from other habitats. This suggests that speciation occurs at similar rates in the deep sea in comparison to other environments. Gene flow estimates between conspecific populations using both the FST and private alleles methods were significantly correlated and both indices are deemed suitable for estimating relative levels of gene flow in deep-sea organisms. Spatial genetic structure in deep-sea populations was also examined, using FST- For deep-sea vertebrates and invertebrates there was no correlation between FST and either scales of geographic separation between populations, or life history characteristics betveen species, but sample size was low. The genetic structure of populations of deep-sea vertebrates showed greater differentiation in transoceanic comparisons than intraoceanic comparisons. At intraoceanic scales, levels of gene flow between conspecific populations are difficult to predict in both invertebrates and vertebrates, possibly because spatial genetic structure at this scale appears to be determined by a complex of historical, biological and environmental parameters. With hydrothermal vent species, higher levels of genetic differentiation are found betveen populations from different ridge segments than between populations on the same ridge segment. Mean FST values were significantly higher with populations from different ridge systems compared to populations from different ridge segments along a single ridge system. In considering anthropogenic impacts on the deep-sea fauna it is suggested that studies of the biochemical and molecular genetics of the organisms would be useful in showing which species are most likely to be affected. Genetic data can indicate sublethal effects of potential pollutants on populations which othenvise appear to be unaffected. |
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