Temporal and genetic variation in female aggression after mating

Abstract

<jats:title>Abstract</jats:title><jats:p>Aggression between individuals of the same sex is almost ubiquitous across the animal kingdom. Winners of intrasexual contests often garner considerable fitness benefits, through greater access to mates, food, or social dominance. In females, aggression is often tightly linked to reproduction, with females displaying increases in aggressive behavior when mated, gestating or lactating, or when protecting dependent offspring. In the fruit fly, <jats:italic>Drosophila melanogaster</jats:italic>, females spend twice as long fighting over food after mating as when they are virgins. However, it is unknown when this increase in aggression begins or whether it is consistent across genotypes. Here we show that aggression in females increases between 2 to 4 hours after mating and remains elevated for at least a week after a single mating. In addition, this increase in aggression 24 hours after mating is consistent across three diverse genotypes, suggesting this may be a universal response to mating in the species. We also report here the first use of automated tracking and classification software to study female aggression in <jats:italic>Drosophila</jats:italic> and assess its accuracy for this behavior. Dissecting the genetic diversity and temporal patterns of female aggression assists us in better understanding its generality and adaptive function, and will facilitate the identification of its underlying mechanisms.</jats:p>

Male condition influences female post mating aggression and feeding in Drosophila

“…If they had shown an intermediate response, this would be more consistent with a dose‐dependent effect. The idea of an ‘on–off’ switch is consistent with another study which found that different genotypes of males do not stimulate different levels of post‐mating aggression in females, despite potential differences in their ejaculates (Bath et al., 2020).…”

“…Across taxa, female aggression can have substantial fitness consequences, with winners in intrasexual aggressive encounters garnering considerable fitness benefits, in the form of increased access to food, better nesting or oviposition sites, protection of their offspring or social dominance (Clutton‐Brock & Huchard, 2013; Rosvall, 2011). In D. melanogaster , mated females spend twice as much time engaging in aggressive interactions as virgin females when competing over food (Bath et al., 2017, 2020; Nilsen et al., 2004). Like other post‐mating responses (PMRs), increased female aggression after mating is stimulated by components of the male ejaculate in this species—females must receive sperm to maximally increase aggression post mating, while the Sfp ‘sex peptide’ is also partially responsible for the increase in aggression after mating (Bath et al., 2017).…”

Mate Competition Drives Aggressive Behaviour in Female Drosophila

“…Previous work in female Drosophila aggression has focused on competition over territory, that is, where two females are fighting over a physical patch of food. Interestingly, in that context mated females are more aggressive than virgin females 31,32,37 , in stark opposition with our own findings in the context of mate competition. This reversal in the relationship between mating status and aggression levels could be due to a shift in the females’ perceived value of available resources: virgin females would value mating partners higher than egg-laying sites, whereas mated females would then prioritize egg-laying site acquisition over possible early rematings.…”

“…We explored how reproductive parameters are affected by aggression and found no clear effect on any of the measured parameters. We show that the amount of aggression displayed in these circumstances has a positive correlation with the female mating drive, which is the opposite of what had previously been reported for food patch competition 31,32 . Finally, we show that food odour is a pre-requisite for these aggressive displays and that conspecific sensing through the odorant receptor OR47b contributes substantially to generate aggressive displays.…”

“…Analogous signals in females have not yet been identified. Another interesting feature of female aggressive behaviour is that it is strongly stimulated by mating 31,32 , which is consistent with the notion that females fight for resources to improve the odds of their offspring. However, in certain circumstances females of other species compete for mates 33–36 .…”