MBE Advance Access originally published online on March 30, 2007
Molecular Biology and Evolution 2007 24(6):1407-1415; doi:10.1093/molbev/msm063
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Research Articles |
Evolution of Population Structure in a Highly Social Top Predator, the Killer Whale
* School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
Department of Genetics, Rutgers University
National Marine Mammal Laboratory, National Marine Fisheries Service, Seattle, Washington
Monterey Bay Cetacean Project, Pacific Grove, California
E-mail: a.r.hoelzel{at}dur.ac.uk.
Accepted for publication March 16, 2007.
Intraspecific resource partitioning and social affiliations both have the potential to structure populations, though it is rarely possible to directly assess the impact of these mechanisms on genetic diversity and population divergence. Here, we address this for killer whales (Orcinus orca), which specialize on prey species and hunting strategy and have long-term social affiliations involving both males and females. We used genetic markers to assess the structure and demographic history of regional populations and test the hypothesis that known foraging specializations and matrifocal sociality contributed significantly to the evolution of population structure. We find genetic structure in sympatry between populations of foraging specialists (ecotypes) and evidence for isolation by distance within an ecotype. Fitting of an isolation with migration model suggested ongoing, low-level migration between regional populations (within and between ecotypes) and small effective sizes for extant local populations. The founding of local populations by matrifocal social groups was indicated by the pattern of fixed mtDNA haplotypes in regional populations. Simulations indicate that this occurred within the last 20,000 years (after the last glacial maximum). Our data indicate a key role for social and foraging behavior in the evolution of genetic structure among conspecific populations of the killer whale.
Key Words: evolution • population genetics • marine mammal • social behavior
Scott Edwards, Associate Editor
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