Epicuticular hydrocarbons (HC) of insects play an essential role in their adaptation to terrestrial environments because they help decrease cuticle permeability to water, thereby reducing the risk of lethal dehydration. (The cuticle is the external, hardened tissue which surrounds the body of an insect. The epicuticle is the outermost layer of the cuticle.) The epicuticular HC also perform a pheromonal function during courtship and mating of some Drosophila species. The principal investigators have discovered that variation in the epicuticular HC profile of male D. mojavensis is responsible for a large proportion of intermale variation in male success--females mate five times more frequently with males whose epicuticular HC profile is similar to that of males raised at 17o C. The proposed research will examine the relationship between variation in the abiotic and biotic environmental factors (temperature, humidity, diet, etc.) that have been found in laboratory experiments to be responsible for variation in epicuticular HC composition, cuticle permeability, and sexual behavior in D. mojavensis. Data for all three parameters will be obtained both in the lab and in the field under natural conditions, in concert with a detailed assessment of the microhabitat climatological regime encountered by male and female D. mojavensis during the course of their daily activities. Additional field and laboratory experiments will assess the impact of variation in the three parameters on the mating system of D. mojavensis. This research is unique in that it promises to identify a biological trait that plays an important role in individual survival as well as reproduction.
