Daven Presgraves, professor of biology at the University of Rochester, has been awarded a 2009 Alfred P. Sloan Foundation Research Fellowship. Presgraves, who is also the 2008-9 Grass Fellow at the Radcliffe Institute for Advanced Study at Harvard University, is one of 118 award recipients who will receive $50,000 toward their research programs over the next two years.
Presgraves works to understand the genetic basis of speciation—the splitting of one species into two species—at the molecular level. One of his key areas of focus is the evolution of biological barriers that keep different species from exchanging genetic material. When one species splits into two, genetic differences accumulate that make the two daughter species reproductively incompatible with one another. These genetic incompatibilities, or "speciation genes", cause species hybrids to be sterile or inviable, preventing two species from fusing back into one.
Scientists expect genetic changes to accumulate in random locations throughout the genome, but Presgraves found instead that speciation genes cluster inexplicably on the X chromosome. 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. With the new funding, Presgraves will investigate why the X chromosome is a hotspot for speciation genes between closely related species. He believes that the X chromosome is misregulated in hybrid males, disrupting sperm production.
Presgraves also finds and characterizes particular speciation genes. "When we cross two fruit flies species that split from one another three million years ago, many of the hybrid offspring die," says Presgraves. "We've now found that a functionally related group of genes is responsible for this incompatibility, with different versions of the genes having evolved by natural selection in the two species." His group recently identified two speciation genes that encode proteins that control molecular traffic into and out of a cell's nucleus. Presgraves describes an arms race of sorts inside the cell that drives these genes to evolve rapidly—and as a consequence makes closely related species genetically incompatible with one another.
Sloan fellowships are designed to fund young scholars in the early stages of their careers. The current winners are faculty members at 61 colleges and universities in the United States and Canada who are conducting research at the frontiers of physics, chemistry, computational and evolutionary molecular biology, computer science, economics, mathematics and neuroscience. The foundation has given more than $103 million to 3,900 researchers since the program began in 1955, thirty eight of which have subsequently received Nobel Prizes.