Inclusive fitness and sexual conflict: How population structure can modulate the battle of the sexes

Abstract

Competition over reproductive opportunities among members of one sex often harms the opposite sex, creating a conflict of interest between individual males and females. Recently, this battle of the sexes has become a paradigm in the study of intersexual coevolution. Here, we review recent theoretical and empirical advances suggesting that -as in any scenario of intraspecific competition -selfishness (competitiveness) can be influenced by the genetic relatedness of competitors. When competitors are positively related (e.g. siblings), an individual may refrain from harming its competitor(s) and their mate(s) because this can improve the focal individual's inclusive fitness. These findings reveal that population genetic structure might be of paramount importance when studying the battle of the sexes. We conclude by identifying some new lines of research at the interface of sexual selection and social evolution.

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

“…Because of the success with which our alternative model is able to predict male-male aggression between non-kin, we propose that the dynamics and structures of social groups (IGEs) may be more important factors both in our experiment and those of Carazo et al [11,30] and should be considered in future studies. Our results join the ranks of many other studies documenting the importance of social structure and their effects on conflict and other social behaviours [13,10,47,48]. …”

“…It has been hypothesized that the magnitude of this conflict may be relaxed in the presence of kin, as an individual can benefit indirectly via the reproductive success of relatives [9,10].…”

Relatedness and age reduce aggressive male interactions over mating in domestic fowl

“…cannibalism, Walls and Roudebush 1991; lethal male fighting, Kapranas et al 2015), including recent work on contexts related to mating (Carazo et al 2014;Martin & Long 2015;Tan et al, in press;reviewed in Díaz-Muñoz et al 2014;Pizzari et al 2015). We present one of few empirical examples where males show increased tolerance towards kin during precopulatory male-male competition.…”

“…More often, however, males are not cooperating, but are in direct competition with each other over mating opportunities (Andersson 1994). Relatedness has the potential to affect the aggressiveness of these competitive interactions (Hamilton 1964;Pizzari and Gardner 2012;Díaz-Muñoz et al 2014;Pizzari et al 2015), as well as during copulation where unrelated rival males should allocate larger ejaculates during sperm competition than related rivals due to kin selected benefits (Parker 2000). However, empirical studies fail to detect such differential responses by males (Australian field cricket, Teleogryllus oceanicus, Thomas and Simmons 2008;bank voles, Myodes glareolus, Klemme and Ala-Honkola 2014; house mouse, Mus musculus domesticus, Ramm and Stockley 2009).…”

“…However, empirical studies fail to detect such differential responses by males (Australian field cricket, Teleogryllus oceanicus, Thomas and Simmons 2008;bank voles, Myodes glareolus, Klemme and Ala-Honkola 2014; house mouse, Mus musculus domesticus, Ramm and Stockley 2009). Further, kin selection can moderate aggression when there are inclusive fitness benefits (Hamilton 1964;Waldman 1988;Pizzari et al 2015). The capacity for relatedness to affect male-male competitive interactions has been demonstrated in 4 nematodes, where higher relatedness mitigates mortality in lethal male fighting (Kapranas et al 2015).…”