Exposure to Rivals Does Not Affect Male Mate Choice in Drosophila melanogaster

Male-male competition can affect male mate choice in different ways, potentially leading to stronger preferences when males benefit from investing more resources in fewer but higher-quality matings or weaker preferences if choosiness could lead to missed mating opportunities. As in many insects, Drosophila melanogaster males show both pre- and postcopulatory preferences for larger, higher-fecundity females. Exposure to rivals alters some aspects of male courtship and mating behavior in this species, but it is unknown whether male mate choice is similarly affected by increased competition. We tested whether perceived competition influenced the strength of male precopulatory and postcopulatory preferences for large females by housing D. melanogaster males with or without rivals before they encountered females that differed in size. Males from both treatments exhibited equally strong courtship preferences for large females and extended matings to a similar degree with large versus small females, indicating that exposure to rivals did not affect these components of male mate choice. There was also no difference in offspring production between males from the two treatments. Our findings suggest that male preferences for large females are relatively stable across social environments in D. melanogaster, supporting the hypothesis that strong, consistent preferences for high-quality mates can be maintained despite variation in competitive contexts.