Abstract:
Ecosystem function and resilience is determined by the interactions and independent contributions of individual species.
Apex predators play a disproportionately determinant role through their influence and dependence on the dynamics of
prey species. Their demographic fluctuations are thus likely to reflect changes in their respective ecological communities
and habitat. Here, we investigate the historical population dynamics of the killer whale based on draft nuclear genome
data for the Northern Hemisphere and mtDNA data worldwide. We infer a relatively stable population size throughout
most of the Pleistocene, followed by an order of magnitude decline and bottleneck during the Weichselian glacial period.
Global mtDNA data indicate that while most populations declined, at least one population retained diversity in a stable,
productive ecosystem off southern Africa. We conclude that environmental changes during the last glacial period promoted
the decline of a top ocean predator, that these events contributed to the pattern of diversity among extant
populations, and that the relatively high diversity of a population currently in productive, stable habitat off South Africa
suggests a role for ocean productivity in the widespread decline.
