Phylogeny of Physid Snails (Basommatophora: Physidae) and Evolution of Reproductive Isolation

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The Physidae (Gastropoda: Basommatophora) is a group of freshwater snails with a native distribution in North, Middle, and South America, and Eurasia, but reach their greatest diversity in North America. The family constitutes a major component of the freshwater molluscan fauna in many lake, pond, and stream habitats. Despite the prominence of physids in behavioral, physiological and ecological studies, little is know of the phylogenetic relationships among the taxa. Furthermore, many questions remain as to whether many of the currently recognized species, subspecies, and "morphs" constitute valid evolutionary entities. Despite nearly 200 years of taxonomic and systematics studies, no rigorous study has been done employing modern methods and analyses. The purpose of the NSF-sponsored research is to collect physid snail specimens representing recognized species, subspecies, and "morphs" to estimate an evolutionary "tree" using on mitochondrial and nuclear gene DNA sequences and shell and anatomical data. In addition, the principal investigators will examine whether the family Physidae constitutes a natural assemblage of snails, being more closely related to each other than to any other group of snails. Although estimating a phylogeny for the ecologically important Physidae is important for its own sake, the resultant evolutionary "tree" will be used in conjunction with a modern, analytically based view of species to test whether currently recognized groups constitute valid species. At a time when species inventories are being made to discover hotspots and prioritize areas for various protection measures, it is imperative that recognized species correspond with phylogenetic species. Furthermore, the researchers will examine the evolution of reproductive isolation among selected physid species by conducting a series of controlled experiments in the laboratory.This research will provide a robust evolutionary "tree" and modern classification of the snail family Physidae. In addition, an empirical examination of species issues in physids will provide important data for estimating how many species actually exist within the family. These data will be of considerable use to conservation and evolutionary biologists as well to federal and state wildlife agency personnel.