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

Authors


  • This paper is one in a series resulting from a long-term study (since 1992) on the population genetics and systematics of Steller‘s sea lions sponsored mainly by NMFS. Joe Hoffman specialises in the molecular ecology of natural vertebrate populations and is also interested in the population genetics of a variety of Antarctic marine organisms. Kanchon Dasmahapatra is a molecular ecologist conducting research in speciation, phylogenetics and conservation genetics. Bill Amos runs the Molecular Ecology group and has a long-standing interest in understanding the distribution of variability in natural populations. His favorite wine of the moment is Chateau Musar 1991, outstanding! Caleb Phillips is interested in molecular evolution and phylogeography. Tom and his research group are responsible for investigating various research questions pertaining to the declining populations of Stellar‘s sea lions contribute to a wide assortment of projects involving animal foraging behaviour, demographics, and abundance estimation to collectively address these questions and provide fisheries management direction. John Bickham‘s research interests focus on genetic mutations and how they are produced and transmitted in individuals, populations, species and the evolutionary processes that affect genetic change. His current research projects include population genetics of Stellar‘s sea lions and bowhead whales, biodiversity studies in bats and ecotoxicological studies in contaminated environments in Azerbaijan.

Joseph I. Hoffman, Fax: +44 1223336676; E-mail: jih24@cam.ac.uk

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.

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