Phylogeny of Didelphid Marsupials, a Taxon-Dense Approach Using Data from Nuclear Genes and Morphology

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A grant has been Sharon Jansa at the University of Minnesota and Dr. Robert S. Voss at the American Museum of Natural History, New York to study the evolutionary history of South American didelphid marsupials (Didelphimorphia: Didelphiadae), commoly known as New World "opossums." The16 extant genera of didelphid marsupials comprise 75 species and represent the most diverse surviving lineage of the old endemic mammalian fauna in South America; today these species constitute the only substantially intact radiation of marsupial mammals outside Australasia. While didelphids have long been of interest to biogeographers and comparative biologists, their evolutionary history remains poorly understood. The principal goal of this project is to infer the historical relationships among didelphid marsupials in order to provide a secure framework for interpreting their evolution and historical biogeography. We will collect and analyze DNA sequence data from five, slowly-evolving nuclear genes with a wide range of biochemical functions for a core group of 42 species representing all 16 genera of didelphid marsupial. The resulting 8 kilobase dataset will be the largest comparative molecular dataset for these species and will provide critical data for reconstructing their evolutionary history.Among other applications, the results of this study will contribute to historical biogeographic research in South America, provide a framework for understanding the morphological evolution of marsupials, and inform the future use of didelphid exemplars in comparative biology and palaeontology. In addition, the resulting database of DNA sequences will provide materials for understanding gene function and the dynamics of molecular evolution in mammalian radiations. Didelphid marsupials have long been overlooked in studies of mammalian systematics and molecular evolution. The results of this study will fill a conspicuous gap in our understanding of mammalian evolutionary biology.awarded to Dr.