January 19, 2011
Principal Investigator: Phillip Morin, Marine Mammal Genetics Group
Killer whales have long been known to be comprised of sympatric 'ecotypes', with discrete prey preferences, morphology and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. New high-throughput DNA sequencing techniques allowed us to sequence the entire mitochondrial genomes from 139 killer whales, and provided strong evidence that most of the killer whale types are evolutionarily distinct from the others, with between 150,000 and 700,000 years of independent evolution.
Future expansion of this study will include analysis of diversity within some ecotypes, expansion of the global sample analysis to include additional geographic and ecotype groups, and use of single nucleotide polymorphisms (SNPs) as an additional genetic marker type to understand patterns of gene flow and differentiation in the nuclear genome.
More Antarctic killer whale research in the Protected Resources Division
Foote, A. D., P. A. Morin, J. W. Durban, R. L. Pitman, P. Wade, E. Willerslev, M. T. P. Gilbert and R. R. Da Fonseca. 2010. Positive selection on the killer whale mitogenome. Biology Letters 7: 116-118
LeDuc, R. G., K. M. Robertson, and R. L. Pitman. 2008. Mitochondrial sequence divergence among Antarctic killer whale ecotypes is consistent with multiple species. Biology Letters 4:426-429.
Morin, P. A., F. I. Archer, A. D. Foote, J. Vilstrup, E. E. Allen, P. Wade, J. Durban, K. Parsons, R. Pitman, L. Li, P. Bouffard, S. A. Nielsen, M. Rasmussen, E. Willerslev, M. T. P. Gilbert and T. Harkins. 2010. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Research 20: 908-916.
Pitman, R. L. and P. Ensor. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetacean Research and Management 5: 131-139.
Pitman, R. L., W. L. Perryman, D. Leroi and E. Eilers. 2007. A dwarf form of killer whale in the Antarctic. Journal of Mammalogy 88: 43-48.