Are flies kind to kin? The role of intra- and inter-sexual relatedness in mediating reproductive conflict

Abstract

As individual success often comes at the expense of others, interactions between the members of a species are frequently antagonistic, especially in the context of reproduction. In theory, this conflict may be reduced in magnitude when kin interact, as cooperative behaviour between relatives can result in increased inclusive fitness. Recent tests of the potential role of cooperative behaviour between brothers in Drosophila melanogaster have proved to be both exciting and controversial. We set out to replicate these experiments, which have profound implications for the study of kin selection and sexual conflict, and to expand upon them by also examining the potential role of kinship between males and females in reproductive interactions. While we did observe reduced fighting and courtship effort between competing brothers, contrary to previous studies we did not detect any fitness benefit to females as a result of the modification of male antagonistic behaviours. Furthermore, we did not observe any differential treatment of females by their brothers, as would be expected if the intensity of sexual conflict was mediated by kin selection. In the light of these results, we propose an alternative explanation for observed differences in male-male conflict and provide preliminary empirical support for this hypothesis.

Kin recognition and co‐operative foraging inDrosophila melanogasterlarvae

“…In adults, flies behave differently towards conspecifics based on the phenotypes associated with the gut microbiomes that develop in different environments (Lizé et al., ), which may also play a role in kin recognition ( e.g . Carazo et al., ; Le Page et al., , but see Martin & Long, ). However, in all our assays all larvae developed in the same type of environment, so they are likely to exhibit very similar microbiotic cues.…”

“…Lizé, McKay, & Lewis, ; Carazo, Perry, Johnson, Pizzari, & Wigby, ; Le Page et al. but see Chippindale et al., ; Martin & Long, ). While larvae are able to recognize each other as conspecifics using vision, smell, mechanosensation and gustation ( reviewed in Dombrovski et al., ), to the best of our knowledge there has been no published evidence that larvae have the ability to distinguish kin from nonkin.…”

Genetic variation in male-induced harm in Drosophila melanogaster

“…3500 adults per generation), wild-type population Ives (hereafter 'IV'), which has been cultured under standardized conditions for hundreds of generations ( [15]; electronic supplementary material). This population harbours considerable genetic variation for many traits, and has been used in a wide range of behavioural ecology and population genetics studies [5,16,21]. The population is cultured on a non-overlapping twoweek schedule, in which they are combined en masse every 14 days and distributed onto fresh media.…”

Inbreeding parents should invest more resources in fewer offspring

“…[13–17]). In the context of sexual conflict over mating decisions, it remains somewhat underappreciated that individuals can increase their inclusive fitness by inbreeding.…”