Intralocus Sexual Conflict and the Genetic Architecture of Sexually Dimorphic Traits in Prochyliza Xanthostoma (Diptera: Piophilidae)

Abstract

Abstract. Because homologous traits of males and females are likely to have a common genetic basis, sex-specific selection (often resulting from sexual selection on one sex) may generate an evolutionary tug-of-war known as intralocus sexual conflict, which will constrain the adaptive divergence of the sexes. Theory suggests that intralocus sexual conflict can be mitigated through reduction of the intersexual genetic correlation (r MF ), predicting negative covariation between r MF and sexual dimorphism. In addition, recent work showed that selection should favor reduced expression of alleles inherited from the opposite-sex parent (intersexual inheritance) in traits subject to intralocus sexual conflict. For traits under sexual selection in males, this should be manifested either in reduced maternal heritability or, when conflict is severe, in reduced heritability through the opposite-sex parent in offspring of both sexes. However, because we do not know how far these hypothesized evolutionary responses can actually proceed, the importance of intralocus sexual conflict as a long-term constraint on adaptive evolution remains unclear. In this study, we investigated the genetic architecture of sexual and nonsexual morphological traits in Prochyliza xanthostoma. The lowest r MF and greatest dimorphism were exhibited by two sexual traits (head length and antenna length) and, among all traits, the degree of sexual dimorphism was correlated negatively with r MF . Moreover, sexual traits exhibited reduced maternal heritabilities, and the most strongly dimorphic sexual trait (antenna length) was heritable only through the same-sex parent in offspring of both sexes. Our results support theory and suggest that intralocus sexual conflict can be resolved substantially by genomic adaptation. Further work is required to identify the proximate mechanisms underlying these patterns.

Heritability and genetic correlation between the sexes in a songbird sexual ornament

“…The population may not be in equilibrium but rather in the transitional stage envisaged in the models of Lande (1980Lande ( , 1987 of rapid, parallel evolution of male and female characters, which hypothetically, would be followed by a phase of selection acting differentially on each sex, with forces of nearly the same magnitude but of opposite sign. That stage seems not yet reached, maybe because the high between-sex genetic correlation makes the evolution of sexual dimorphism an exceedingly slow process (Lande, 1980(Lande, , 1987Bonduriansky and Rowe, 2005;Bonduriansky and Chenoveth, 2009;Poissant et al, 2009). Once exposed to selection, however, all agents of natural and sexual selection on the ornament may not be necessarily coincident in both sexes and/or, given the differences in additive genetic variance (Table 1; h 2 z values), would result in similar responses (Lynch and Walsh, 1997;Badyaev, 2002).…”

“…The intersexual genetic correlation r MF was estimated with the expression Oh 2 FD h 2 MS /h 2 MD h 2 FS , where h 2 are the bootstrapped heritabilities (10 000 bootstrap iterations) calculated from father-daughter (FD), mother-daughter (MD), mother-son (MS) and father-son (FS) covariances (Bonduriansky and Rowe, 2005).…”

“…The phenotypic correlation was estimated from the correlation among male and female full-sib means of standardised FP size (Bonduriansky and Rowe, 2005). Differences between heritability estimates were tested through analysis of covariance (Lynch and Walsh, 1997).…”

The quantitative genetics of sexual dimorphism: assessing the importance of sex-linkage

“…Sex-limited autosomal gene expression is also expected to reduce COV Amf (Reeve and Fairbairn, 2001). Most authors predict a similar trend in r Amf (Fisher, 1958;Eisen and Legates, 1966;Lande, 1980Lande, , 1987Arnold, 1985;Bonduriansky and Rowe, 2005), but this latter expectation is somewhat more tenuous because r Amf depends on the additive genetic variances in each sex in addition to the covariance and may not change in parallel with COV Amf (Reeve and Fairbairn, 2001). …”

QTL mapping for sexually dimorphic fitness-related traits in wild bighorn sheep

“…QTLs with sex-specific effects have been documented in a variety of organisms (for example, Nuzhdin et al, 1997;Farber and Medrano, 2007;Moghadam et al, 2007) including domestic sheep ), but to our knowledge had never been documented in a free-living wildlife population. The presence of sex-specific QTL effects in bighorn sheep adds to the accumulating evidence suggesting that sexual selection alters the genetic architecture of quantitative traits by promoting the accumulation of sex-specific genetic variance (Moller 1993;Wilkinson 1993;Bonduriansky and Rowe, 2005;Wright et al, 2008;Robinson et al, 2009).…”