Tanya Verma, Bodhisatta Nandy

Mate guarding (MG) mediated by aggression towards rivals can be a significant contributor to male reproductive fitness in many animal species. However, establishing the MG effect of aggression in species without explicit MG can be difficult. While aggression in the fruit fly Drosophila melanogaster is well documented, only recently has it been connected to MG. Interestingly, males of this species can show plasticity in aggression depending on number of rivals. In view of the MG effect of aggression, we predicted that such plasticity should be more prominent around their immediate mate compared to an arbitrary female. We quantified aggression in males belonging to two treatments – solitary and group (plasticity treatment), in presence of either their immediate mate or an arbitrary female (mate type treatment). Surprisingly, there was no significant effect of either mate type treatment or plasticity treatment, nor there was any effect of the interaction. This indicates that there is no plasticity in aggression after a male has acquired mating and MG is unlikely to be the basis of aggression towards rival males. Thus, we did not find any evidence of MG in our system. We argue that laboratory adapted populations are often subject to the artefacts of Genotype × Environment interactions and/or inbreeding, leading to variable results across studies.