Molecular Systematics and the Evolution of Habitat Specificity

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Crandall 9702338 Phylogenetics is a field of study that is of central importance to others such as ecology, molecular biology, systematics, and evolutionary biology. As applications of phylogenetics increase, so too does the breadth of ~ese applications. From molecular studies of the biochemical function of genes, to human studies such as transmission patterns in HIV-I, "phylogenetic thinking" has lead to major discoveries in a broad array of disciplines. The object of this study is to bring phylogenetics to a broader array of peop e through high school outreach, museum displays, and undergraduate/graduate education. In addition, phylogenetic thinking is pervasive in my research program. The primary research goal is to establish phylogenetic relationships among the 24 species within the two sister subgenera of freshwater crayfishes, Jug~cambarus and Glareocola (Decapoda: Cambaridae). Once phylogenetic relationships are established, the PI will test the monophyly of these two subgenera relative to representatives from five other subgenera within the genus Cambarus. Phylogenetic estimates will be based on nucleotide sequences from the 1 6S region of the mitochondrial genome and the nuclear gene astacin. Once,a phylogeny is estimated and monophyly is established, the PI will explore the evolutionary biology of habitat specificity using comparative methods. The beauty of this group of freshwater crayfishes is that they are distributed into the four main ecotypes within which crayfishes are found: lotic waters (8 species), lentic waters (5 species), primary burrowers (semi-terrestrial, 5 species), and caves (subterranean, 6 species). Therefore, they provide a unique opportunity to study the evolution of habitat specificity in crayfishes. Do crayfishes invade a habitat and radiate within that habitat? Is there a repeated evolutionary sequence of habitat specificity, such as lotic to lentic, to burrower, to cave? Or are habitat specif~cities randomly distributed over the phylogeny? The PI's research will address these questions and use the answers as examples of the utility of the phylogenetic approach in my educational programs.