"We identified a gene in N. vitripennis that we thought was responsible for its unique scent," said Josh Gibson, an ASU doctoral student working with Jrgen Gadau, a professor in School of Life Sciences in the College of Liberal Arts and Sciences. "Then, we successfully conducted an experiment to suppress that gene, which actually changed the composition of the sex pheromone, so that it resembled that of the other species," Gibson added.
Female N. vitripennis wasps did not respond when offered the new pheromone alone. They responded only when it was combined with the two original, or ancestral, scents. In addition, females from a closely related species, Nasonia giraulti, did not distinguish between the new and ancestral sex pheromones, regardless of whether there were two or three scents.
Thus, the researchers concluded that the N. vitripennis females did not react to the third component when it first evolved. Instead, they adapted to the new smell over time and now it is an integral part of the species-specific sex pheromone of N. vitripennis males.
This study is one of the few where researchers have identified genes that prevent a species from breeding with another closely related species. The findings provide new insights into the evolution of genes that contribute to speciation, or the formation of new species, as well as the evolution of diverse sex pheromones.
"The females use this smell to distinguish between the species," said Gibson. "This is important. If an individual wasp were to mate with a different species, it would be very costly because they would not produce viable offspring. We learned that the smell difference is based on a single and simple chemical change. Basically, this is the way the female wasp can find Mr. Ri
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Arizona State University