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

Clabaut, C.; Herrel, A.; Sanger, T.; Smith, T. B.; Calsbeek, A. Development of beak polymorphism in the African seedcracker, Pyrenestes ostrinus. Evolution and Development 2009, 11, 636–646. PDF online.
Delaney, K. S.; Pires, D.; Holder, K.; Bardeleben, C.; Smith, T. B. Isolation of polymorphic tetranucleotide microsatellite markers for the black-bellied seedcracker (Pyresnestes ostrinus). Molecular Ecology Notes 2005, 5, 774–776. PDF online.
Keith, S.; Smith, T. B. Pyrenestes. In The birds of Africa; Fry, C. H., Keith, S. ., Urban, E. K., Eds.; Princeton University Press: Princeton, MA, 2004; pp 317–324. online.
Smith, T. B.; Schneider, C. J.; Holder, K. Refugial isolation vs. ecological gradients: Testing alternative mechanisms of evolutionary divergence in four rainforest vertebrates. Genetica 2001, 112, 383–398. PDF online.
Slabbekoorn, H.; Smith, T. Does bill size polymorphism affect courtship song characteristics in the African finch Pyrenestes ostrinus?. Biological Journal of the Linnean Society 2000, 71, 737–753. PDF online.
Smith, T. B.; Girman, D. Reaching new adaptive peaks: Evolution of bill size polymorphism in an African finch. In Adaptive Genetic Variation in the Wild; Mousseau, T. ., Sinervo, B. ., Endler, J. ., Eds.; Oxford University Press: Oxford, 2000. online.
Smith, T. B. Adaptive significance of the mega-billed form in the polymorphic finch Black-bellied Seedcracker Pyrenestes ostinus. Ibis 1997, 139 (2), 382–387; DOI 10.1111/j.1474-919X.1997.tb04638.x. online.
Skúlason, S.; Smith, T. B. The ecology of resource polymorphisms in vertebrates: a reply. Trends in Ecology and Evolution 1996, 11. PDF online.
Smith, T. B.; Skúlason, S. Evolutionary significance of resource polymorphisms in fish, amphibians and birds. Annual Review of Ecology and Systematics 1996, 27, 111–133. PDF online.
Smith, T. B.; Bruford, M. W.; Wayne, R. K. The preservation of process: the missing element of conservation programs. In Biodiversity Letters; : 1993; pp 164–167. PDF online.
Smith, T. B. Disruptive selection and the genetic basis of bill size polymorphism in the African finch Pyrenestes. Nature 1993, 363, 618–620. PDF online.
Smith, T. B. Ecological and evolutionary significance of a third bill form in the polyomphic finch Pyrenestes ostrinus. In Birds and the African Environment: Proceedings of the Eighth Pan-African Ornithological Congress; Wilson, R. T., Ed.; Annals Musee Royal de l’Afrique Central (Zoologie): Tervuren, Belgium, 1993. online.
Smith, T. B. Inter- and intra-specific diet overlap during lean times between Quelea erythrops and bill morphs of Pyrenestes ostrinus. Oikos 1991, 60, 76–82. PDF online.
Smith, T. B. A double-billed dilemma. Natural History 1991, 100 (1), 14–21. online.
Smith, T. B. Patterns of morphological and geographic variation in trophic bill morphs of the African finch Pyrenestes. Biological Journal of the Linnean Society 1990, 41, 381–414; DOI 10.1111/j.1095-8312.1990.tb00842.x. online.
Smith, T. B. Natural selection on bill characters in the two bill morphs of the African finch Pyrenestes ostrinus. Evolution 1990, 44, 832–842. PDF online.
Smith, T. B. Resource use by bill morphs of an African finch: Evidence for intraspecific competition. Ecology 1990, 71, 1246–1257. PDF online.
Smith, T. B. Comparative breeding biology of the two bill morphs of the Black-bellied Seedcracker (Pyrenestes ostrinus). The Auk 1990, 107, 153–160. online.
Smith, R. J.; Smith, T. B. Portable device for measuring seed-hardness. Journal of Field Ornithology 1989, 60, 56–59. online.
Kirkpatrick, C. E.; Smith, T. B. Blood parasites of birds in Cameroon. Journal of Parasitology 1988, 74, 1009–1013. online.
Smith, T. B. Bill size polymorphism and interspecific niche utilization in an African finch. Nature 1987, 329, 717–719. PDF online.
Smith, T. B.; Smith, P. B. Cracking the problem of bill size. Riverbanks 1987, 5, 2–8. online.

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Center for Tropical Research | UCLA Institute of the Environment and Sustainability
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