The interaction between male courtship plasticity and female mate choice in Drosophila melanogaster
Authors: Samuel Marston 1; Dean Castillo 1,2
Affiliations: 1) University of Utah, SLC, UT; 2) University of Nebraska at Omaha, Omaha, NE
Keywords: f. speciation; g. courtship and mating
Sexual selection drives rapid speciation by creating divergence in sexual signals and preferences. Geographically isolated populations of D. melanogaster exhibit strong asymmetric behavioral isolation and divergence in male courtship behavior. These lineages are often classified into Z-type lineages from Southern Africa and M-type lineages that occur outside of Africa. Z-type females almost exclusively choose Z-type males over M-type males in mate choice assays. Both Z-type and M-type males adjust their courtship behavior depending on the genotype of the female they are courting. This behavioral plasticity could potentially optimize male mating success when encountering diverse females. However, the mechanism responsible for triggering a plastic behavioral response is unknown. Males might respond to female behavioral feedback or female chemical cues. To determine which female trait facilitates male courtship plasticity we quantified courtship behaviors, focusing on the time spent singing, for males interacting with females wherein we have genetically manipulated their cuticular hydrocarbon (CHC) profile. Using a Z-type male strain that exhibits strong plasticity, we quantified the time spent singing when interacting with an M-type female and a Z-type female to establish baseline plasticity. We then tested these males with the Z-type females in which the coding sequence of the gene desat2 was replaced using CRISPR, creating a null mutant. The gene desat2 contributes to the production of the CHC 5,9-heptacosadiene (5,9-HD) a compound that is characteristic of Z-type females. This CHC is an isomer of the CHC 7,11 HD which is the most abundant CHC in M-type (non-African) females. Our Z-desat2 null strain has a CHC profile resembling an M-type female but in choice tests behaves like a Z-type female. Thus we believe this genotype would provide an M-type chemical cue to a male but Z-type like behavioral feedback. We hypothesized that if males use these heptacosadiene isomers to adjust their courtship we would expect to see male courtship of Z-desat2 null females resemble courtship of M-type females. This experiment will determine which cue triggers male courtship plasticity and how this might contribute to the evolution of reproductive isolation, furthering our understanding of the co-evolution of male behavior and female preference of closely related populations.