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Evolution and Development

Developmental mechanisms of small-scale adaptive evolutionary changes: adaptive speciation, convergence/parallelism; modularity, evolvability and constraint of beak shapes in Darwin's finches and related birds.

Darwin's Finches

The faces of vertebrates are often readily recognizable as they display a number of species-specific characteristics. For example, the classic textbook example of adaptive radiation, natural selection and niche partitioning in animals is the fifteen closely related species of Darwin’s finches (Thraupidae, Passeriformes), whose primary diversity is in the size and shape of their beaks. This natural morphological diversity is associated with the exploitation of various ecological resources and its developmental basis is not fully understood. It is likely that this stunning diversity of beaks in Darwin’s finches and cranial morphology in vertebrates more generally was produced by alterations in their craniofacial developmental genetics. To reveal the molecular causes for such striking variation, we previously employed “candidate genes” and microarray screen approaches, both extremely productive – some key genetic pathways, such as Bmp4 and Calmodulin have been identified and reported. We are currently employing a combination of genetic, genomic, molecular, bioinformatics, 2-D and 3-D imaging and modeling approaches to understand evolution of adaptive beak shapes in Darwin’s Finches and their close relatives from the monophyletic tribe Tholospiza (which also includes Caribbean bullfinches, bananaquits and grassquits). These birds represent interesting stories of both adaptive radiation and morphological convergence. These projects are done in collaboration with Drs. Peter and Rosemary Grants (Princeton), the world’s experts on Darwin’s finches; Dr. Michael Brenner (SEAS, Harvard), who designs ways to model the beak shape evolution; Dr. Kevin Burns (SDSU), the leading expert on Tholospiza phylogeny, and many others. In our laboratory, these projects have been carried out by Dr. Winston Kuo, Dr. Celine Clabaut, Dr. Ricardo Mallarino, and current lab members Dr. Masayoshi Tokita and graduate student Michael Brent Hawkins.