CTR - Evolution of Resource Plymorphisms

Summary

Region:
Africa (Cameroon)

The black-bellied seedcracker (Pyrenestes ostrinus) is unusual among birds in exhibiting a non-sex related polymorphism in bill size and represents one of the few examples of disruptive selection in natural populations. Research on this species focuses on understanding the ecological and evolutionary mechanisms maintaining trophic polymorphisms in birds. This work has included measuring natural selection in natural populations, examining the genetic basis of traits through breeding experiments, and investigating ecological aspects of diet, feeding behavior and competition. Despite increasing evidence of the widespread occurrence of resource polymorphisms in vertebrates, little is known about their genetic basis.

Understanding the genetic basis of a polymorphism when the ecological basis is well understood, as in seedcrackers, has the potential of lending important insights into the evolution of discrete variation and the genetic basis of adaptation. We are currently using molecular genetic approaches to examine the population structure and phylogenetic histories of bill morphs in order to understand how disruptive selection may lead to speciation and we are exploring which genes are involved in generating bill variation.

Related Publications

2005	Delaney, K. S., D. Pires, K. Holder, C. Bardeleben C., and T. B. Smith. Isolation of polymorphic tetranucleotide microsatellite markers for the black-bellied seedcracker (Pyrenestes ostrinus). Molecular Ecology Notes 5: 774-776. PDF
2004	Keith, S., and T. B. Smith. Pyrenestes. Pages 317-324. In C. H. Fry, S. Keith, and E. K. Urban (Eds.). The Birds of Africa, Volume VII. Princeton University Press, Princeton and Christopher Helm, London.
2001	Smith, T.B., C.J. Schneider and K. Holder. Refugial isolation vs. ecological gradients: Testing alternative mechanisms of evolutionary divergence in four rainforest vertebrates. Genetica 112: 383-398. PDF
2000	Slabbekoorn, H. and T. B. Smith. Does bill size polymorphism affect courtship song characteristics in the African finch Pyrenestes ostrinus? Biological Journal of the Linnean Society 71: 737-753. PDF
2000	Smith, T. B. and D. Girman. Reaching new adaptive peaks. Evolution of bill size polymorphism an African finch. Pages 139-156. In T. Mousseau, B. Sinervo and J. Endler (Eds.). Adaptive Genetic Variation in the Wild. Oxford University Press, Oxford.
1997	Smith, T. B. Adaptive significance of the mega-billed form in the polymorphic finch Black Bellied Seedcracker Pyrenestes ostinus. Ibis 139: 382-387.
1996	Skúlason, S. and T. B. Smith. The ecology of resource polymorphisms in vertebrates: a reply. Trends in Ecology and Evolution 11: 26. PDF
1996	Smith, T. B. and Skúlason, S. Evolutionary significance of resource polymorphisms in fish, amphibians and birds. Annual Review of Ecology and Sytematics 27: 111-133. PDF
1996	Smith, T. B., M. W. Bruford, and R. K. Wayne. The Preservation of Process: The Missing Element of Conservation Programs (from Biodiversity Letters). Pages 71-75. In Samson, F. B. and F. L. Knopf (Eds.). Ecosystem Management: Selected Readings. Springer-Verlag, New York.
1995	Skúlason, S. and T. B. Smith. Resource polymorphisms in vertebrates. Trends in Ecology and Evolution 10: 366-370. PDF
1993	Smith, T. B. Disruptive selection and the genetic basis of bill size polymorphism in the African finch Pyrenestes. Nature 363: 618-620. PDF
1993	Smith, T. B. Ecological and Evolutionary Significance of a Third Bill Form in the polymorphic Finch Pyrenestes ostrinus. Pages 61-66. In Wilson, R. T. (Ed.). Birds and the African Environment: Proceedings of the Eighth Pan-African Ornithological Congress. Annals Musee Royal de l'Afrique Central (Zoologie) 268, Tervuren, Belgium.
1991	Smith, T. B. Inter- and intra-specific diet overlap during lean times between Quelea erythrops and bill morphs of Pyrenestes ostrinus. Oikos 60: 76-82.
1991	Smith, T. B. A doubled-billed dilemma. Natural History 1: 14-21.
1990	Smith, T. B. Patterns of morphological and geographic variation in trophic bill morphs of the African finch Pyrenestes. Biological Journal of the Linnean Society 41: 381-414.
1990	Smith, T. B. Natural selection on bill characters in the two bill morphs of the African finch Pyrenestes ostrinus. Evolution 44: 832-842. PDF
1990	Smith, T. B. Resource use by bill morphs of an African finch: Evidence for intraspecific competition. Ecology 71: 1246-1257. PDF
1990	Smith, T. B. Comparative breeding biology of the two bill morphs of the Black-bellied Seedcracker (Pyrenestes ostrinus). Auk 107: 153-160.
1989	Smith, R. J., and T. B. Smith. Portable device for measuring seed-hardness. Journal of Field Ornithology 60: 56-59.
1988	Kirkpatrick, C. E., and T. B. Smith. Blood parasites of birds in Cameroon. Journal of Parasitology 74: 1009-1013.
1987	Smith, T. B. Bill size polymorphism and interspecific niche utilization in an African finch. Nature 329: 717-719. PDF
1987	Smith, T. B., and P. B. Smith. Cracking the problem of bill size. Riverbanks 5: 2-8.

Evolution of Resource Polymorphisms

Summary

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