Biologists have long studied island radiations to understand how both adaptation and geographic isolation have interacted to generate ecological diversity. The Hawaiian archipelago has been a productive place to undertake such speciation studies, because its extreme isolation from continental sources of immigrants and its highly variable environments have spurred spectacular radiations of the few lineages to have successfully colonized it. This project investigates the mechanisms and tempo of diversification of the 26+ species of Hawaiian tephritid flies, which have likely radiated from a single colonizing ancestor in less than 3 million years. These insects feed on plant species found only in Hawaii, including most members of the Hawaiian silversword alliance, a classic model of adaptive radiation; many feed on the seeds and thus have a direct impact on reproduction of their host plants, some of which are federally endangered species. In collaboration with talented undergraduate research students, Dr. Jonathan Brown will undertake field and laboratory studies to (1) survey likely plant hosts from across the archipelago to determine the geographic range and mode of host use for all species; and (2) determine the evolutionary relationships among all the species, based on information from multiple gene sequences. These evolutionary relationships will then be used examine the role of geographic isolation vs. adaptive changes to different host-plants in the speciation process. The results will provide a framework for future studies of the evolution of behavioral and morphological traits, e.g., melanin wing patterns, a key trait used to identify tephritids and some other groups of flies. Understanding the evolution of these traits will contribute to a better understanding of this diverse family of insects, which includes many pest species of economic importance.
Knowledge of the evolutionary processes that play out on island archipelagos like Hawaii is important for understanding their conservation value, especially given current threats to their unique native species. This research project will also provide several undergraduate students with summer research experiences that demonstrate the strength of interdisciplinary research in organismal, molecular, and conservation biology. Students will be well prepared for these experiences via an NSF-supported core biology curriculum at Grinnell College that emphasizes research-based learning and integration across biological subdisciplines. Dr. Brown is committed to recruiting research students who have participated in Grinnell's New Science Project, an innovative program designed to encourage under-represented groups to pursue scientific careers. As in his previous work, students will be full partners in the gathering, analysis and dissemination of the results of the study. By providing independent research opportunities within a biology curriculum centered on skills of inquiry, this project will continue both the Dr. Brown's and Grinnell College's proven tradition of integrating scientific research into a broad and meaningful liberal arts education.
