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Open Access Research article

Multi-locus phylogeography of the dusky dolphin (Lagenorhynchus obscurus): passive dispersal via the west-wind drift or response to prey species and climate change?

April D Harlin-Cognato1*, Tim Markowitz2, Bernd Würsig3 and Rodney L Honeycutt4

Author Affiliations

1 Department of Zoology, Michigan State University, 203 Natural Sciences Building, East Lansing, MI 48824, USA.

2 Dusky Dolphin Research Project, Muritai, 13 Maui Street, Kaikoura, New Zealand.

3 Marine Mammal Research Program, Department of Marine Biology, Texas A&M University, 4700 Ave. U, Galveston, Texas 77551, USA.

4 Pepperdine University, Natural Science Division, 24255 Pacific Coast Highway, Malibu, California 90263, USA.

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BMC Evolutionary Biology 2007, 7:131  doi:10.1186/1471-2148-7-131

Published: 3 August 2007

Abstract

Background

The dusky dolphin (Lagenorhynchus obscurus) is distributed along temperate, coastal regions of New Zealand, South Africa, Argentina, and Peru where it feeds on schooling anchovy, sardines, and other small fishes and squid tightly associated with temperate ocean sea surface temperatures. Previous studies have suggested that the dusky dolphin dispersed in the Southern Hemisphere eastward from Peru via a linear, temperate dispersal corridor provided by the circumpolar west-wind drift. With new mitochondrial and nuclear DNA sequence data, we propose an alternative phylogeographic history for the dusky dolphin that was structured by paleoceanographic conditions that repeatedly altered the distribution of its temperate prey species during the Plio-Pleistocene.

Results

In contrast to the west-wind drift hypothesis, phylogenetic analyses support a Pacific/Indian Ocean origin, with a relatively early and continued isolation of Peru from other regions. Dispersal of the dusky dolphin into the Atlantic is correlated with the history of anchovy populations, including multiple migrations from New Zealand to South Africa. Additionally, the cooling of the Eastern Equatorial Pacific led to the divergence of anchovy populations, which in turn explains the north-south equatorial transgression of L. obliquidens and the subsequent divergence of L. obscurus in the Southern Hemisphere.

Conclusion

Overall, our study fails to support the west-wind drift hypothesis. Instead, our data indicate that changes in primary productivity and related abundance of prey played a key role in shaping the phylogeography of the dusky dolphin, with periods of ocean change coincident with important events in the history of this temperate dolphin species. Moderate, short-term changes in sea surface temperatures and current systems have a powerful effect on anchovy populations; thus, it is not infeasible that repeated fluctuations in anchovy populations continue to play an important role in the history of coastal dolphin populations.