Contrasting patterns of genetic diversity at three different genetic markers in a marine mammal metapopulation

Abstract

Many studies use genetic markers to explore population structure and variability within species. However, only a minority use more than one type of marker and, despite increasing evidence of a link between heterozygosity and individual fitness, few ask whether diversity correlates with population trajectory. To address these issues, we analysed data from the Steller's sea lion, Eumetiopias jubatus, where three stocks are distributed over a vast geographical range and where both genetic samples and detailed demographic data have been collected from many diverse breeding colonies. To previously published mitochondrial DNA (mtDNA) and microsatellite data sets, we have added new data for amplified fragment length polymorphism (AFLP) markers, comprising 238 loci scored in 285 sea lions sampled from 23 natal rookeries. Genotypic diversity was low relative to most vertebrates, with only 37 loci (15.5%) being polymorphic. Moreover, contrasting geographical patterns of genetic diversity were found at the three markers, with Nei's gene diversity tending to be higher for AFLPs and microsatellites in rookeries of the western and Asian stocks, while the highest mtDNA values were found in the eastern stock. Overall, and despite strongly contrasting demographic histories, after applying phylogenetic correction we found little correlation between genetic diversity and either colony size or demography. In contrast, we were able to show a highly significant positive relationship between AFLP diversity and current population size across a range of pinniped species, even though equivalent analyses did not reveal significant trends for either microsatellites or mtDNA.

Patterns of genetic variation across the distribution range of the cockle Cerastoderma edule inferred from microsatellites and mitochondrial DNA

“…Discrepancies in diversity patterns between mtDNA and microsatellite markers have already been reported in previous studies (Brito 2007;Hoffman et al 2009). Sex-biased Table 3 Pairwise Fst values based on eight (a) or six (b) microsatellites (above diagonal) and the cyt b gene (below diagonal) for the three main regions defined by clustering analysis a Significant at 5 % level dispersal, selective sweeps and marker response to demographic processes are usually invoked to account for such discrepancies.…”

Fine-scale genetic structure of bottlenose dolphins, Tursiops truncatus, in Atlantic coastal waters of the Iberian Peninsula

“…blue whiting, Micromesistius poutassou) in their diet and dissimilar stable isotope signatures (Fernández, 2010;Fernández et al, 2011). It is also generally recognised that higher levels of genetic diversity usually occur towards the centre of a species' range while subsequent founder events could originate a stepwise loss of microsatellite diversity (Hoffman et al, 2009). The low levels of genetic diversity found in dolphins from southern Galicia suggest that, despite the lack of physical barriers, this population inhabits peripheral areas and gene flow with adjacent sites is restricted.…”

Phylogeography of Steller sea lions: relationships among climate change, effective population size, and genetic diversity

“…The results of this study provide a detailed scenario for the history that has shaped contemporary populations of E. jubatus. An intensive research effort into the biology of the endangered Steller sea lion (Eumetopias jubatus) has resulted in significant advances in our understanding of the evolutionary history, population structure, demographic trends, physiology, ecology, and evolution of this species (Baker et al 2005;Bickham et al 1996Bickham et al , 1998Harlin-Cognato et al 2006;Hoffman et al 2006Hoffman et al , 2009Kenyon and Rice 1961;Loughlin et al 1987Loughlin et al , 1992O'Corry-Crowe et al 2006;Phillips et al 2009aPhillips et al , 2009bTrites and Donnelly 2003). For example, population genetic and phylogenetic investigations have demonstrated clear population structure at rookery, region, and stock levels, with phylogenetic delineation increasing at broader geographic groupings (Baker et al 2005;Bickham et al 1996Bickham et al , 1998O'Corry-Crowe et al 2006).…”