THE ADULT COMPONENT OF SELECTION IN DROSOPHILA-MELANOGASTER - SOME ASPECTS OF EARLY-REMATING ACTIVITY OF FEMALES

As an important factor of the adult component of selection, mating beh aviour was studied in Drosophila melanogaster, with emphasis on non-vi rgin females. We found that 30-50 per cent of the females in a laborat ory population will remate within 6 h of first mating under no-choice conditions. This high percentage of early rematings was not due to the continuous confinement of the females with males but indicated a rapi d return of receptivity of a significant proportion of the females. Re mating behaviour was significantly influenced by both the genotype of the female and the genotype of her two successive partners. Age of fem ales was only important insofar as it concerned young, 1 or 2-day old, females. These females showed less remating than older females. Willi ngness to remate was also affected by the number of sperm stored. Fema les that had been inseminated by less fertile males, i.e. males that h ad already mated two or three times, showed higher remating percentage s than females inseminated by more fertile males. Notwithstanding this sperm effect, females were estimated to remate approximately every se cond day. It is suggested that a high frequency of remating and the re sulting sperm competition are significant components of Drosophila lif e-history.