February 14, 2013
Finding Mr. Right: Understanding The Evolution Of Sex Pheromones In Wasps
April Flowers for redOrbit.com - Your Universe Online
How do you look for your perfect mate? Perhaps you take long walks on the beach, share a candlelight dinner, have a virtual date on Skype; or maybe it's smelling that scent of just the right perfume.
When it comes to finding the perfect mate in the insect world, especially for a member of one particular wasp species, it only takes a whiff of the special love potion to know you have found "Mr. Right."
Most insects rely on their sense of smell when looking for a mate, unlike humans and their dating rituals. Sex pheromones play an important role, researchers have found, in finding a suitable partner of the same species. Little is known, however, about the evolution and genetic basis of these smells.
An international team of researchers from Arizona State University, the University of Regensburg, the Zoological Research Museum Alexander Koenig Bonn (Museum Koenig), and the Technical University Darmstadt in Germany studied two species of the parasitic wasp genus Nasonia to understand the evolution of sex pheromones. The team asked the question, "if male sex pheromones are used as unique mating signals to attract females, and if female wasps will not mate with males that have different pheromones, then how did the vast array of these scents evolve in insects?"
They found that all known species of Nasonia wasp have pheromones containing two elements, except one species, Nasonia vitripennis, which includes a novel third element. Less than half the size of a grain of rice, these tiny wasps lay their eggs in developing flies. The two species examined for this study are found in the same part of the Eastern U.S. and prefer laying their eggs in similar types of flies. This means they have many opportunities to choose the wrong mate.
"We identified a gene in N. vitripennis that we thought was responsible for its unique scent," Josh Gibson, an ASU doctoral student working with JÃ¼rgen Gadau, a professor in School of Life Sciences in the College of Liberal Arts and Sciences (CLAS), said in a statement.
"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.
Females of the N. vitripennis species did not respond when they were offered just the new pheromone, instead they only responded when it was combined with the two original or ancestral scents. N. giraulti, on the other hand, did not distinguish between the new and ancestral sex pheromones, regardless of whether or not there was a third scent involved. N. giraulti is a close relative of N. vitripennis.
N. vitripennis females did not react to the third component when it first evolved, the team concluded. Instead, they believe, 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, published in a recent issue of Nature, is one of the few where researchers have identified genes that prevent two closely related species from breeding. Besides illuminating the evolution of sex pheromones, the findings provide new insights into the evolution of genes that contribute to speciation, or the formation of new species.
"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. Right."