Strategic sperm allocation in the small white butterfly Pieris rapae (Lepidoptera: Pieridae).

摘要

Recovery rates of non-fertile apyrene and fertile eupyrene sperm number and spermatophore size were studied in polyandrous P. rapae. The mass of the 1st spermatophore increased with time since eclosion, as did the number of both sperm types. On a male's 2nd mating, both spermatophore mass and sperm number increased with time since the 1st mating. However, the rate of increase in eupyrene sperm numbers was higher after the 1st mating. The difference in the rate of increase may be the result of different probabilities of virgin and non-virgin males obtaining future matings. Males retained sperm in the duplex after their 1st mating. This ensured that high sperm numbers were available for their 2nd mating, even when remating only 1 h later. Thus, males did not ejaculate all available sperm on any given mating, and appear to have different strategies on their 1st and 2nd matings. It is concluded that P. rapae males allocate sperm strategically according to the probability of obtaining subsequent matings and the level of sperm competition.