Daven Presgraves, assistant professor of biology, has won a David and Lucile Packard Foundation fellowship to explore the genetic basis of the origin of species. The $875,000 fellowship, one of twenty awarded nationally by the foundation, will help Presgraves find the 'speciation genes' that cost cross-species hybrids the ability to reproduce.
"The Packard award is a terrific honor, and it provides a great opportunity for us to tackle one of the burning questions in our field—what kinds of evolutionary changes in the genome cause one species to split into two species?" says Presgraves. "We recently found that the X chromosome plays a special role in speciation, but we don't yet understand why. Going forward, we'll combine comparative genomics, genetic mapping and molecular biology to get the answer."
Presgraves focuses on the barriers—such as speciation genes on the X chromosome—that prevent different species from exchanging genetic material. When one species splits into two, interbreeding between the two daughter species is much more likely to produce sterile hybrids when the species exchange X chromosomes than when they exchange any other chromosomes, says Presgraves. The phenomenon, dubbed the "large X-effect," acts as a wedge that evolves early during the formation of two newly formed species, pushing them onto divergent evolutionary paths.
Scientists expect evolutionary changes in DNA to accumulate in random locations across a genome, but Presgraves instead found that most changes causing hybrid sterility cluster inexplicably on the X chromosome. With the new funding, he will investigate why the X chromosome is a hotspot for "speciation genes" that prevent genetic exchanges between closely related species. Presgraves believes there is something special about the X chromosome that attracts genes that disrupt the creation of sperm in hybrid males.
The David and Lucile Packard Foundation Fellowship Program has awarded 424 fellowships during its 20-year history, totaling approximately $260 million, to faculty members at 50 top national universities. It is among the nation's largest nongovernmental program designed to support unusually creative researchers early in their careers. The Fellowship Program funds research in a broad range of disciplines including physics, chemistry, mathematics, biology, astronomy, computer science, earth science, ocean science and all branches of engineering.