Evolution of reproductive behaviour in response to selection for increased pathogen resistance in Drosophila melanogaster

Abstract

Both immune response and reproductive behaviour are important life-history related traits that govern the fitness of the organism. Given that both of these are costly traits, trade-offs between the two are to be expected when resources are limiting. In this study I explored evolution of sexual behaviour in a population of Drosophila melanogaster that has been selected for higher survivorship against a pathogen Pseudomonas entemophila. I found that immune response is positively affected by higher sexual activity in selected populations, whereas mortality in control populations remained unaffected by the degree of sexual activity. I have also shown that under infected condition males from selected population mate and court less frequently than the control populations under the same conditions. Further study has been conducted exploring if this is a trade-off between reproductive effort and immune response or an evolved reproductive strategy deployed by selected males. The study shows that there is no fitness benefit of higher survivorship post-infection in the selected males compared to control males. There are evidences suggesting a possible trade-off between reproductive behaviour and mounting an immune response.