Evolution of Resource Polymorphisms


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

2009 Clabaut, C., A. Herrel, T. Sanger, T. B. Smith, and A. Abzhanov. Development of beak polymorphism in the African seedcracker, Pyrenestes ostrinus. Evolution & Development 11: 636-646. PDF
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. PDF
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.


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Center for Tropical Research | UCLA Institute of the Environment and Sustainability
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The Center for Tropical Research, located on the third floor of La Kretz Hall, is part of the Institute of the Environment and Sustainability at the University of California, Los Angeles. For general inquiries, contact Christa Gomez, CTR Office Manager, at 310-206-6234, or by email at cgomez@lifesci.ucla.edu. Visitors are always welcome.

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