Effects of reproductive state and host resource experience on mating decisions in a walnut fly

Prior experience with conspecifics or essential resources, aswell as physiological condition, can have important influenceson an animal's reproductive behavior. While effects of experienceand physiological state (such as reproductive condition) aregenerally treated separately in theoretical discussions, theyoften interact. No previous study has attempted to distinguisheffects of experience on physiological state from other effectsof experience in the context of mating behavior. In a studyof a walnut-infesting tephritid fly (Rhagoletis juglandis),we examined the effects of host fruit experience on mating behavior.We manipulated physiological state in terms of egg load (definedas the number of mature oocytes in a female's ovaries) independentlyof fruit experience to distinguish the effects of these variables.We found that females with high egg loads were significantlymore likely to copulate than low–egg load females; thelevel of fruit experience had no effect on propensity to copulate,except via effects on egg load. In contrast, females with priorexposure to fruit copulated for a significantly shorter durationthan control females, while egg load had no effect on copulationduration. These results suggest that female reproductive conditionand exposure to essential resources can have important, albeitdiverse effects on mating behavior. We discuss how distinguishingdifferent types of variables may provide insight into sexualconflict over mating decisions, as well as which sex controlsspecific aspects of behavior.