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Population genomics of the killer whale indicates ecotype evolution in sympatry involving both selection and drift.

Moura, A.E. and Kenny, J.G. and Chaudhuri, R. and Hughes, M.A. and Welch, A.J. and Reisinger, R.R. and de Bruyn, P.J.N. and Dahlheim, M.E. and Hall, N. and Hoelzel, A.R. (2014) 'Population genomics of the killer whale indicates ecotype evolution in sympatry involving both selection and drift.', Molecular ecology., 23 (21). pp. 5179-5192.

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.

Item Type:Article
Keywords:Adaptation, Cetacea, Ecological genetics, Population genomics, Sympatric divergence.
Full text:(VoR) Version of Record
Available under License - Creative Commons Attribution.
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1111/mec.12929
Publisher statement:© 2014 The Authors. Molecular Ecology published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Date accepted:15 September 2014
Date deposited:20 July 2015
Date of first online publication:12 October 2014
Date first made open access:No date available

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