The influence of glacial epochs and habitat dependence on the diversity and phylogeography of a coastal dolphin species: Lagenorhynchus albirostris

Abstract

In this paper we use mitochondrial and microsatellite DNA variation to investigate the mechanisms that underlie the evolution of population structure in a highly mobile marine mammal, the white-beaked dolphin. We found moderate genetic diversity (h) at mtDNA, but low nucleotide diversity (π) (0.7320 ± 0.0031 and 0.0056 ± 0.0004, respectively), consistent with expectations for a recent expansion. Analyses based on mismatch distributions further suggested a demographic expansion in the Norwegian-Barents Sea population and a spatial expansion in the British isles-North Sea population, implying distinct demographic histories. F ST values showed clear differentiation among these two populations, but no difference was found between putative populations separated by the English Channel. Our data suggest a stepwise pattern of expansion, dependent on available coastal habitat. The conservation implications are a need to protect local populations isolated by an expanse of deep water, and in particular, a population along the British coasts and in the North Sea as separate from the North Norway-Barents Sea population. It is also evident that overall diversity was reduced, probably during the last glacial epoch.