Genetically effective population sizes of Antarctic seals estimated from nuclear genes

Abstract

We analyzed eight nuclear microsatellite loci in three species of Antarctic seals; Weddell seal (Leptonychotes weddellii; mean N = 163), crabeater seal (Lobodon carcinophaga; 138) and Ross seal (Ommatophoca rossii; 35). We estimated genetic diversity (T) and effective population size (N E) for each species. Autosomal microsatellite based N E estimates were 151,200 for Weddell seals, 880,200 for crabeater seals, and 254,500 for Ross seals. We screened one X-linked microsatellite (Lw18), which yielded similar N E estimates to the autosomal loci for all species except the Ross seals, where it was considerably larger (~103 times). Microsatellite N E estimates were comparable with previously published N E estimates from mitochondrial DNA, but both are substantially lower than direct estimates of population size in all species except the Ross seals. The ratio of maternally versus biparentally derived estimates of N E for Ross seals was not consistent with the hypothesis that they are a polygynous species. We found no sign of a recent, sustained genetic bottleneck in any of the species.