Interspecific competition between Drosophila melanogaster and D. simulans: Effects of adult

Abstract

The hatchability of eggs laid by D. simulans st and D. melanogaster Or-R-C in consecutive 12-hour periods was measured for the first seven days post eclosion in a replicated experiment where adult density at six levels, species frequency at two levels, and 32P tissue content at two levels were varied factorially. A similar experiment was done for D. simulans st and D. melanogaster yw. In both experiments, all unhatched eggs were classified as either dead or infertile. Least-squares analyses of variance on arcsine-transformed percentage data indicated that the three strains produced significantly different proportions of hatched, dead, and infertile eggs. Increased adult density significantly decreased the proportion of hatched eggs (and increased the proportion of dead eggs) for D. simulans st and D. melanogaster Or-R-C, but not for D. melanogaster yw. Effects of strain frequency were not significant for D. simulans st or D. melanogaster Or-R-C, but for D. melanogaster yw higher hatchability and lower proportions of infertile eggs were obtained in pure populations. Hatchability varied between periods; changes in hatchability being random (but significant) for D. melanogaster yw, and consistent (but not significant) for D. simulans st (a decrease in hatchability with time) and D. melanogaster Or-R-C (an increase with time). The competing strain of D. melanogaster did not influence the proportions of hatched, dead or infertile eggs from D. simulans st.