The Genetic Basis of Sexual Selection, Speciation

Until recently, studies of species formation focused on the complex behavioral changes in mating behavior and sexual selection. Mammals, birds, insects and reptiles all have novel--and sometimes multiple--ways of attracting mates: Singing, dancing, displaying their colors or sporting big horns. But little is known about the genetic basis of mating and courtship rituals, and how this relates to the formation of species.

University of Arkansas professor of biological sciences William Etges has organized a symposium to discuss the latest research in the genetics of mate choice and species formation. The symposium speakers have also written chapters, along with others in the field, that will become part of a book on the subject, edited by Etges and professor Mohamed Noor of Louisiana State University.

The symposium, titled "Genetics of mate choice: From sexual selection to sexual isolation," will be held on Saturday, July 13, at the Society of American Naturalist meeting in Banff, Alberta, Canada.

Etges, himself will present his research at the symposium. He specializes in the genetic history of drosophila, fruit flies, focusing on species that populate cacti in North and South America. Because fruit flies have diversified into thousands of species, reproduce quickly and create many generations in a short time, scientists use them to study evolution, population genetics and diversification.

Male fruit flies use pheromones and "love songs"--vibrations made by rubbing their wings together--to attract females. These strategies differ between species; in other words, songs that attract females of one fruit fly species may be spurned by another.

Etges and his colleagues have received funding from the National Science Foundation to use standard gene mapping techniques to locate the genes that influence these traits.

The researchers will use an "Insectivox" to record the wing vibrations of the male fruit flies, and an automated gas chromatograph to single out the hydrocarbon pheromone signals produced by the males. They will gather fruit flies on trips to Mexico and crossbreed the insects, then look for differences in the songs, the pheromones and the genes.

In many cases, genetic information on fruit flies is obtained from laboratories--a setting that bears little resemblance to the insect's typical surroundings. In this case, the researchers have studied the particular fruit fly that interests them in its natural habitat--cactus plants in the Sonoran Desert of northern Mexico.

"We've got a host of ecological information on these desert flies," Etges said. The ecological, behavioral and genetic information combine to create a more thorough portrait of the history of species formation.

Etges will be one of eight presenters at the symposium. Researchers at the symposium will talk about the mating characteristics of lacewings, guppies, bacteria, crickets and fruit flies.

With the increasing availability and ease of use of molecular genetic techniques, researchers have begun to probe the genetic basis of species formation

"Male-female mate signaling is the glue that keeps species together," Etges said. "What causes these signaling systems to break down or reorganize is what we're interested in, because then we should have a better understanding of how new species are formed."