Evolution of reduced mate harming tendency of males in Drosophila melanogaster populations selected for faster life history

Abstract: Detrimental effect of males on female, often termed mate harm, is a hallmark of sexual conflict. Allowed to evolve unchecked, mate harming traits are predicted to bring down average fitness of a population, unless mitigated by the evolution of resistance in females. In addition, life history may also modulate sexual conflict, but the mechanism is not clearly understood. Here we investigated the evolution of mate harm in a set of experimentally evolved laboratory populations of Drosophila melanogaster, wherein a faster aging has evolved in response to > 1000 generations of selection for faster development and early reproduction. We quantified mortality and fecundity of Oregon R females held with evolved and ancestral males to show that the evolved males are significantly less detrimental to their mates. We compared our results from the evolved males with that from a phenocopied version of the ancestral regime males to show that only part of the observed difference in mate harm can be attributed to the evolved difference in body size. We further show that the reduction in mate harming ability evolved despite an increase in courtship activity, especially early in life. We discuss the causative role of an evolved reproductive schedule and altered breeding ecology. Significance statement: Sexually antagonistic male effects can significantly bring down female fitness. Along with female counter evolution of resistance traits, life history has been conjectured to impose constrains on the evolution of such harming ability in males. Here, we report the evolution of mate harming ability in males of a set of five replicate Drosophila melanogaster populations that evolved smaller size and faster aging as a result of > 1000 generations of experimental evolution for faster development and early reproduction. We show that in spite of ample scope of sexual selection, the faster aging males have evolved reduced mate harming ability despite being more active in courting their mates. To the best of our knowledge, this is one of the first clear evidences demonstrating the causal relationship between evolution of life history and reduction in sexual antagonism in a population.