Present address: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071-3166, USA
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Patterns of genetic variation in the adaptive radiation of New World crossbills (Aves: Loxia)
Article first published online: 12 MAY 2006
DOI: 10.1111/j.1365-294X.2006.02895.x
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How to Cite
PARCHMAN, T. L., BENKMAN, C. W. and BRITCH, S. C. (2006), Patterns of genetic variation in the adaptive radiation of New World crossbills (Aves: Loxia). Molecular Ecology, 15: 1873–1887. doi: 10.1111/j.1365-294X.2006.02895.x
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Present address: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071-3166, USA
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Present address: USDA-ARS, Beneficial Insects Introduction Research Lab, 501 South Chapel Street, Newark, Delaware 19713-3814, USA
Publication History
- Issue published online: 12 MAY 2006
- Article first published online: 12 MAY 2006
- Received 22 September 2005; revision received 19 December 2005; accepted 7 January 2006
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Keywords:
- adaptive radiation;
- AFLP;
- ecological speciation;
- genetic structure;
- incipient species;
- Loxia curvirostra
Abstract
Incipient species groups or young adaptive radiations such as crossbills (Aves: Loxia) present the opportunity to investigate directly the processes occurring during speciation. New World crossbills include white-winged crossbills (Loxia leucoptera), Hispaniolan crossbills (Loxia megaplaga), and red crossbills (Loxia curvirostra complex), the last of which is comprised of at least nine morphologically and vocally differentiated forms (‘call types’) where divergent natural selection for specialization on different conifer resources has been strongly implicated as driving diversification. Here we use amplified fragment length polymorphism (AFLP) markers to investigate patterns of genetic variation across populations, call types, and species of New World crossbills. Tree-based analyses using 440 AFLP loci reveal strongly supported clustering of the formally recognized species, but did not separate individuals from the eight call types in the red crossbill complex, consistent with recent divergence and ongoing gene flow. Analyses of genetic differentiation based on inferred allele frequency variation however, reveal subtle but significant levels of genetic differentiation among the different call types of the complex and indicate that between call-type differentiation is greater than that found among different geographic locations within call types. Interpreted in light of evidence of divergent natural selection and strong premating reproductive isolation, the observed genetic differentiation suggests restricted gene flow among sympatric call types consistent with the early stages of ecological speciation.