Plastic responses of males and females interact to determine mating behavior

Abstract

Individuals can respond plastically to variation in their social environment. However, each sex may respond to different cues and contrasting aspects of competition. Theory suggests that the plastic phenotype expressed by one sex can influence evolutionary dynamics in the other, and that plasticity simultaneously expressed by both sexes can exert sex-specific effects on fitness. However, data are needed to test this theory base. Here, we examined whether the simultaneous expression of adaptive plasticity by both sexes of Drosophila melanogaster fruit flies in response to their respective social environments interacts to determine the value of key reproductive traits (mating latency, duration, and fecundity). To vary social environments, males were kept alone, or with same sex rivals, and females were kept alone, in same-sex, or mixed-sex groups. Matings were then conducted between individuals from all of these five social treatments in all combinations, and the resulting reproductive traits measured in both "choice" and "no-choice" assays. Mating latency was determined by an interaction between the plastic responses of both sexes to their social environments. Interestingly, the mating latency response occurred in opposing directions in the different assays. In females exposed to same-sex social treatments, mating latency was more rapid with rival treatment males in the choice assays, but slower with those same males in no-choice assays. In contrast, mating duration was determined purely by responses of males to their social environments, and fecundity purely by responses of females. Collectively, the results show that plastic responses represent an important and novel facet of sexual interactions.

Socially plastic responses in females are robust to evolutionary manipulations of adult sex ratio and adult nutrition

“…We observed no differences in mating duration in females held alone or in groups prior to mating across any of the sexual selection or nutrition regimes. Hence, although females have the potential to influence mating duration [54], the results are consistent with previous reports that plasticity in extended mating duration is primarily under male control [26,52,55].…”

“…It is possible that the general culturing procedures used to maintain the sex ratio and nutritional regimes used here conferred consistent benefits of plasticity in mating latency. This could be due to greater predictability of the conditions experienced by the experimental evolution regimes (specified densities, timings of culturing stages and non overlapping generations) in comparison to normal cage culture used for the wild type flies used in previous studies, in which this effect was not observed [31, 52]. We do not yet know the drivers of plasticity in mating latency.…”

The reduction of nuptial gifts in sclerosomatid Opiliones coincides with increased behavioural sexual conflict

“…An increase in overall association time might serve several functions originally fulfilled by nuptial gifts, with copulation success and paternity share potentially benefiting through increased opportunity to clasp and reduced competition from other males. Furthermore, the exceptionally low latency between first contact and first attempt in L. euserratipalpe might be driven by a variety of factors, although many which might normally influence latency are controlled in this experiment, such as female age or sexual history, male starvation, and the presence of male rivals (Burke & Bonduriansky 2018; Dmitriew & Blanckenhorn 2012; Fowler et al 2022). Low latency has previously been associated with both high conflict (Blanckenhorn et al 2020; Skwierzyńska & Plesnar-Bielak 2018), and in concert with the elevated guarding duration in L. euserratipalpe this low latency likely indicates a species with high conflict.…”

Female fruit flies use social cues to make egg clustering decisions

“…This attraction could arise because it allows females to copy the site-selection choices of others (37, 38, 40) to enable cooperative feeding among larvae (42), or to gain other public goods benefits of egg clustering, as outlined above. Existing evidence suggests that female Drosophila can adjust their fecundity responses according to their previous or current social environments, with females laying fewer eggs after pre-mating exposure to conspecifics (9, 43) but laying eggs more quickly within larger current post-mating social groups (32).…”