Biol . Lett . Michiels and Nils Anthes

(1019 articles) evolution (733 articles) behaviour Articles on similar topics can be found in the following collections Email alerting service here right-hand corner of the article or click Receive free email alerts when new articles cite this article-sign up in the box at the top The study of sexually antagonistic (SA) traits remains largely limited to dioecious (separate sex), mobile animals. However, the occurrence of sexual conflict is restricted neither by breeding system (the mode of sexual reproduction, e.g. dioecy or hermaphroditism) nor by sessility. Here, we synthesize how variation in breeding system can affect the evolution and expression of intra-and inter-locus sexual conflicts in plants and animals. We predict that, in hermaph-rodites, SA traits will (i) display lower levels of polymorphism; (ii) respond more quickly to selection; and (iii) involve unique forms of inter-locus conflict over sex allocation, mating roles and selfing rates. Explicit modelling and empirical tests in a broader range of breeding systems are necessary to obtain a general understanding of the evolution of SA traits. 1. INTRODUCTION The evolutionary interests of the sexes (or 'sex functions' in hermaphrodites) frequently diverge, potentially generating sexual conflict. Independent trait optimization for each sex (or sex function) is often impossible, owing to interactions between the sexes during reproduction or intersexual genetic correlations (Chapman et al. 2003). The resulting conflicts occur through two mechanisms. Intralocus conflict occurs when a trait has different male and female optima, thus generating opposing selection pressures (Rice & Chippindale 2001). Interlocus conflict occurs when optimal male (female) expression at one locus perturbs females (males) from their optimum at another locus (Parker 1979). It is well established that sexual conflict has important evolutionary consequences in dioecious animals (Arnqvist & Rowe 2005; Parker 2006), but it may also occur in simultaneous hermaphrodites (Charnov 1979; Morgan 1994; Michiels & Koene 2006) and in systems such as plants, where mates do not interact physically during reproduction (Murphy 1998; Bernasconi et al. 2004; Levitan 2008). Here, by comparing the expression and the resolution of sexual conflict in the case of simultaneous hermaphroditism and dioecy, we explore how breeding system variation may modify the evolution of sexually antagonistic (SA) traits.