The evolutionary genetics of sexual size dimorphism in the cricket Allonemobius socius

Abstract

In recent years, investigations into the evolution of sexual size dimorphism have moved from a simple single trait, single sex perspective, to the more robust view of multivariate selection acting on both males and females. However, more accurate predictions regarding selection response may be possible if some knowledge of the underlying sex-specific genetic architecture exists. In the striped ground cricket, Allonemobius socius, females are the larger sex. Furthermore, body size appears to be closely associated with fitness in both males and females. Here, we investigate the role that genetic architecture may play in affecting this pattern. Employing a quantitative genetic approach, we estimated the sex-specific selection gradients and the (co)variance matrix for body size and wing morphology (that is, either a long-winged flight-capable phenotype or a short-winged flightless phenotype) to predict phenotypic change in the next generation. We found that the sexes differed significantly in their selection gradients as well as several of their genetic parameters. Our predictions of next-generation change indicated that the within-sex genetic correlations, as well as the between-sex genetic correlations, should play a significant role in sexually dimorphic evolution in this system. Specifically, the female size response was increased by approximately 178% when the between-sex genetic correlations were considered. Thus, our predictions reinforce the notion that genetic architecture can produce counterintuitive responses to selection, and suggest that even a complete knowledge of the selection pressures acting on a trait may misrepresent the trajectory of trait evolution.

Male Bias in Distributions of Additive Genetic, Residual, and Phenotypic Variances of Shared Traits

“…Of the 21 studies that statistically tested for male and female differences in heritabilities, 12 found significant differences in a subset of the traits examined (Mousseau and Roff 1989;Wilcockson et al 1995;Ashman 1999Ashman , 2003Mignon-Grasteau 1999;Jensen et al 2003;Rolff et al 2005;Ng et al 2006;Fedorka et al 2007;Zillikens et al 2008;Gershman et al 2010;Stillwell and Davidowitz 2010).…”

Testosterone, growth and the evolution of sexual size dimorphism

“…Recently, physiologists, geneticists and developmental biologists have sought to integrate this ultimate perspective with an understanding of the proximate mechanisms that facilitate the expression of dimorphic phenotypes from a genome that is largely shared between the sexes (Rhen, 2007). A major goal of this integrative approach is to reconcile the observed phylogenetic lability of SSD with theoretical expectations that its evolution should be highly constrained because of inter-sexual genetic correlations (Lande, 1980(Lande, , 1987Fairbairn & Roff, 2006;Bonduriansky, 2007;Delph, 2007;Fedorka et al, 2007). One resolution to this paradox may be that males and females share most of the same genomic architecture for growth and body size, but that these shared genes are differentially regulated by sex-specific modifiers (Badyaev, 2002).…”

What Is Indirect Cryptic Female Choice? Theoretical Considerations and an Example from a Promiscuous Earwig

“…In crickets Allonemobius socius, larger males provide larger nuptial gifts (hemolymph), which promote female egg production (Fedorka and Mousseau 2002a, b). Male body size is highly heritable in this species (Fedorka et al 2007), indicating that this species is a promising candidate of this CFC mechanism.…”