Sexual and ecological selection on a sexual conflict gene

Abstract

Sexual conflict is often associated with arms race dynamics, which can lead to enhancement of traits involved in the conflict or their replacement with new traits that are more effective in securing reproductive interests of their bearers (Brockhurst et al., 2014; Rowe, Chenoweth, & Agrawal, 2018). Such dynamics result in a series of selective sweeps at one or more loci (Rowe et al., 2018) or generate positive selection in a group of molecules of similar function (Swanson, Clark, Waldrip-Dail, Wolfner, & Aquadro, 2001). In theory, however, sexual conflict could also promote polymorphism at the underlying genes (Brockhurst et al., 2014; Rowe et al., 2018). Such polymorphism could increase the potential of a population to respond to environmental change, which often initially relies on standing genetic variation (Barrett & Schluter, 2008). Yet, processes driving polymorphism in genes involved in sexual conflict received far less attention compared to those leading to escalatory arms race. One mechanism potentially maintaining polymorphism in genes involved in sexual conflict is negative frequency-dependent selection, resulting from Red-Queen dynamics analogous to antagonistic coevolution between hosts and parasites (Brockhurst et al., 2014; Rowe et al., 2018). Another potential mechanism involves negative pleiotropy (Zajitschek & Connallon, 2018), where a trait beneficial to male competitiveness is associated with detrimental pleiotropic effects on other fitness components. For example, in the soay sheep, a gene causing expression of enlarged horns, a trait beneficial to male reproductive success, has a negative pleiotropic effect on survival (Johnston et al., 2013). However, this sexually selected trait does not seem to be involved in sexual conflict.

Sex-biased demography modulates male harm across the genome

“…point out [ 32 ], there are cases where the phenotypic interactions are well understood, but the genetics is not, and cases where the genetics is well understood, but the phenotypic interactions are not. Nonetheless, there are an increasing number of examples that span this gap, including genes underpinning the morphological aspects of grasping behaviours in water striders [ 80 , 81 ], metabolic genes associated with siring success in bulb mites [ 82 – 84 ], and gamete-recognition proteins in abalone and sea urchins [ 85 , 86 ]. Alongside these specific examples, there are classes of male harm traits that may be particularly amenable to large-scale genetic analysis.…”

“…R. Soc. B 288: 20212237 gap, including genes underpinning the morphological aspects of grasping behaviours in water striders [80,81], metabolic genes associated with siring success in bulb mites [82][83][84], and gamete-recognition proteins in abalone and sea urchins [85,86]. Alongside these specific examples, there are classes of male harm traits that may be particularly amenable to largescale genetic analysis.…”

Sexual conflict in a changing environment

“…For example, it seems that decreased temperature removes IASC over the expression of genes associated with male morphs in the bulb mite (Plesnar‐Bielak et al ., 2018 ; Skwierzyńska et al ., 2018 ). At the same time, it reduces the selective advantage of the 6Pdgh allele associated with increased male competitiveness and lowered fitness of females mating with males possessing this allele (Plesnar‐Bielak, Skwierzyńska & Radwan, 2020 ; see Appendix S1), thus also relaxing IECS. Theoretically, the same environmental change can even relax IASC and magnify IESC or vice versa so that the relative intensity of IASC and IESC might depend on ecological conditions.…”