Population genomics of the killer whale indicates ecotype evolution in sympatry involving both selection and drift |
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Authors: | Andre E. Moura John G. Kenny Roy Chaudhuri Margaret A. Hughes Andreanna J. Welch Ryan R. Reisinger P. J. Nico de Bruyn Marilyn E. Dahlheim Neil Hall A. Rus Hoelzel |
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Affiliation: | 1. School of Biological and Biomedical Sciences, Durham University, , Durham, DH1 3LE UK;2. Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, , Liverpool, L69 7ZB UK;3. Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, , Pretoria, South Africa;4. National Marine Mammal Laboratory, National Marine Fisheries Service, , Seattle, WA, 98115 USA |
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Abstract: | The evolution of diversity in the marine ecosystem is poorly understood, given the relatively high potential for connectivity, especially for highly mobile species such as whales and dolphins. The killer whale (Orcinus orca) has a worldwide distribution, and individual social groups travel over a wide geographic range. Even so, regional populations have been shown to be genetically differentiated, including among different foraging specialists (ecotypes) in sympatry. Given the strong matrifocal social structure of this species together with strong resource specializations, understanding the process of differentiation will require an understanding of the relative importance of both genetic drift and local adaptation. Here we provide a high‐resolution analysis based on nuclear single‐nucleotide polymorphic markers and inference about differentiation at both neutral loci and those potentially under selection. We find that all population comparisons, within or among foraging ecotypes, show significant differentiation, including populations in parapatry and sympatry. Loci putatively under selection show a different pattern of structure compared to neutral loci and are associated with gene ontology terms reflecting physiologically relevant functions (e.g. related to digestion). The pattern of differentiation for one ecotype in the North Pacific suggests local adaptation and shows some fixed differences among sympatric ecotypes. We suggest that differential habitat use and resource specializations have promoted sufficient isolation to allow differential evolution at neutral and functional loci, but that the process is recent and dependent on both selection and drift. |
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Keywords: | adaptation Cetacea ecological genetics population genomics sympatric divergence |
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