FEMALE FITNESS IN DROSOPHILA-MELANOGASTER - AN INTERACTION BETWEEN THE EFFECT OF NUTRITION AND OF ENCOUNTER RATE WITH MALES

Female Drosophila melanogaster were maintained at five levels of nutri tion, with either continuous or intermittent exposure to males. Remati ng frequency increased with nutrition and was higher with continuous e xposure to males. Age-specific and lifetime egg production increased w ith increasing nutrition, but lifespan peaked at intermediate nutritio n. Females on the three highest nutritional levels showed a cost of ma ting in reduced survival, but only at the highest food level did this reduced lifespan lead to a significant cost of mating for lifetime egg production. The data suggest that remating frequencies in laboratory cultures may evolve to a low enough level for the cost of mating to be only weakly expressed, if at all. Further data are required to assess the importance of the cost of mating in natural populations, where th e evolution of low remating frequencies might be expected to be oppose d by other costs.