How does breeding system variation modulate sexual antagonism?

Abstract

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 hermaphrodites, SA traits will (i) display lower levels of polymorphism; (ii) respond more quickly to selection; and (iii) involve unique forms of interlocus 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.

Intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic animals

“…There is no a priori reason to assume that sexually antagonistic variation and intra-locus sexual conflict cannot occur in hermaphrodites, as was pointed out by Bedhomme et al [16]. Just as for gonochorists, we should be able to distinguish between inter-locus and intra-locus sexual conflict.…”

“…This effect is probably less pronounced in hermaphrodites since sexually antagonistic alleles will be exposed to selection in both sexes within the lifetime of the individual, leading to a greater efficiency of selection [16]. On the other hand, one way intra-locus sexual conflict can be at least partially resolved is via the evolution of sexual dimorphism [5,17].…”

“…On the other hand, one way intra-locus sexual conflict can be at least partially resolved is via the evolution of sexual dimorphism [5,17]. Simultaneous hermaphrodites cannot evolve sexual dimorphism, so intra-individual sexual antagonism may therefore represent more of a cost or a constraint in hermaphrodites than intra-locus sexual conflict does in gonochorists [16]. Despite a greater efficiency of selection in hermaphrodites and a higher cost of intra-individual sexual antagonism, we should still expect to see some sexually antagonistic variation in hermaphroditic organisms for a number of reasons.…”

“…However, none of these papers examined the potential importance of intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic organisms. Similarly, a recent paper by Bedhomme et al [16] discussed the relevance of inter-and intra-locus sexual conflict in hermaphrodites, but although they raised a number of interesting points, the shortness of their paper did not permit a thorough development. It is not so surprising that intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic animals have been more or less overlooked to date, since the evolution of sexual dimorphism is predicted to be an indicator of sexually antagonistic selection pressures (past or present [17]).…”

Sexual conflict and sex allocation

“…Schärer & Janicke (2009) also do much to highlight the fact that the links between sex allocation and sexual conflict deserve further study across hermaphrodites and organisms with separate sexes. Similarly, Bedhomme et al (2009) initiate a discussion of the differences in how traits selected under the influence of sexual conflict will behave in hermaphrodites in comparison to plants and animals with separate sexes.…”