9724790 Etges This U.S.-Mexico award will support Dr. William Etges of the University of Arkansas in a research collaboration with Dr. Miguel Armella Villalpando of the Universidad Autonoma Metropolitana (Iztapalapa campus) in Mexico. The researchers plan to study patterns of host use among insect species to analyze resource associations and degree of host plant switching among ancestral and derived groups. In particular, they plan to study the host relationships of the D. repleta group species, a cactophilic large group within the genus Drosophila thought to have originated in New World deserts, including the cactus-rich arid lands of central Mexico. This collaboration will allow the location and identification of cactus hosts of D.repleta in the deserts of central Mexico and will increase our understanding of the evolution of this particular group species, which, despite concentrated research efforts over the last 50 years, remains poorly understood. Using phylogenetic relationships among these species, currently derived using molecular approaches, the researchers propose to use patterns of host use to gain insight into the processes of biological diversification that have given rise to this large species group. ***