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Ecological, morphological and genetic divergence of sympatric North Atlantic killer whale populations

Authors

  • ANDREW D. FOOTE,

    1. Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, George Street, Cromarty, IV11 8YJ, UK
    2. Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark
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  • JASON NEWTON,

    1. NERC Life Sciences Mass Spectrometry Facility, SUERC, East Kilbride, G75 0QF, UK
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  • STUART B. PIERTNEY,

    1. Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
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  • ESKE WILLERSLEV,

    1. Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark
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  • M. THOMAS P. GILBERT

    1. Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark
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  • A.D.F. studies evolutionary processes in marine mammals, principally killer whales, with a particular focus on the interaction between ecology, phenotype and genotype. J.N. studies animal and plant ecology through the use of stable isotope including ontogenetic and geographic variation in marine mammals. S.B.P. is a molecular ecologist with a focus on understanding the causes and consequences of variation in levels of genetic diversity among natural populations. E.W. works in the fields of ancient DNA, DNA degradation, and evolutionary biology, with a particular interest in ancient sedimentary and ice core genetics. M.T.P.G is a molecular biologist with broad scale evolutionary, anthropological and archaeological interests that he studies using both modern and ancient DNA.

Andrew Foote, Fax: +441381600548; E-mail: a.d.foote@abdn.ac.uk

Abstract

Ecological divergence has a central role in speciation and is therefore an important source of biodiversity. Studying the micro-evolutionary processes of ecological diversification at its early stages provides an opportunity for investigating the causative mechanisms and ecological conditions promoting divergence. Here we use morphological traits, nitrogen stable isotope ratios and tooth wear to characterize two disparate types of North Atlantic killer whale. We find a highly specialist type, which reaches up to 8.5 m in length and a generalist type which reaches up to 6.6 m in length. There is a single fixed genetic difference in the mtDNA control region between these types, indicating integrity of groupings and a shallow divergence. Phylogenetic analysis indicates this divergence is independent of similar ecological divergences in the Pacific and Antarctic. Niche-width in the generalist type is more strongly influenced by between-individual variation rather than within-individual variation in the composition of the diet. This first step to divergent specialization on different ecological resources provides a rare example of the ecological conditions at the early stages of adaptive radiation.

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