Dynamics of an adaptive radiation: the sigmodontine rodents of South America.

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The rapid increase in the number of species caused by natural selection is known as adaptive radiation. Adaptive radiations are the most dramatic and well-known examples of evolution. They are also often thought to be one of the most important causes of the diversity of life on Earth, but they have only been well documented in a small number of cases. This project will reveal how important natural selection may have been in the adaptive radiation of mammals. It will help develop new methods to study the degree of influence of natural selection in evolutionary history. Understanding how predictable natural selection has been would allow a much better understanding of many features of a species, from its biochemistry to its morphology. Teasing apart the relative roles of adaptation and inherited traits will improve the efficiency of any research that compares different species, such as biomedical studies, using mice, rats, or other species, to understand human health. This project will also help train the next generation of scientists, from high school to graduate students and post-doctoral researchers. Three-dimensional images of hundreds of species will be posted online and made available to other researchers to use in their studies. These images will provide a valuable source of data for scientists and will be a valuable educational tool for teachers and students.This project will test whether one of the most important diversification events in mammals, the taxon Oryzomyalia, a group of over 350 rodent species that descended from a single colonization of South America 7-10 million years ago, was an adaptive radiation. Next-generation DNA sequencing will resolve the very rapid diversification early after colonization. New DNA sequence data will be added to existing data to yield a largely complete phylogeny of at least 330 species. Diverse aspects of their phenotype, including teeth, skull,limbs, vertebrae, fur, and climatic tolerances, will be measured for 265 species. Model-based methods will test for an early rapid phenotypic divergence with subsequent slow-down. Divergence patterns will be explored in finer detail, testing for radiations within subgroups. Finally, information on the genetic correlations among traits will be used to estimate the strength of selection that occurred on each branch of the phylogeny.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.