Mating success is predicted by the interplay between multiple male and female traits in the small hairy maggot blowfly
Intersexual selection drives the evolution of reproductive traits, including ornamentation and courtship behaviour. However, most studies attempting to explain the relationships between reproductive traits are oversimplified because traits are evaluated independently, and assessment of mate choice is restricted to one sex. Further research is required to understand the extent to which interactions between traits influence mating decisions in both sexes. The small hairy maggot blowfly, Chrysomya varipes, offers an ideal opportunity to examine how interactions between foreleg ornamentation (males have conspicuous white and black hairs, whereas females have only black hairs) and complex courtship behaviour influence mating success in males and females. This study involved mate choice trials between single females and males that varied in foreleg ornamentation. Courtship investment was quantified for males, and ornamentation and body size were quantified for both sexes. Mating success was predicted by time invested in courtship, but not by either male and female ornamentation or body size alone. However, there was a significant interaction between courtship investment, ornamentation and body size. At any given courtship investment, males with more ornamentation had an increased probability of mating success. Females with more ornamentation also had an increased probability of mating success, because males invested more courtship in more ornamented females. Furthermore, the lightest males had an increased probability of mating success compared to the heaviest males, as lighter males invested more in courtship. Female weight, however, did not significantly affect the probability of mating. The results suggest that male foreleg ornamentation in C. varipes acts as an amplifier of the visual courtship display, adding to a small but growing body of evidence that multiple male and female traits can interact to influence mating decisions.