Elimination of a Genetic Correlation Between the Sexes via Artificial Correlational Selection

Abstract

Genetic correlations between the sexes can constrain the evolution of sexual dimorphism and be difficult to alter, because traits common to both sexes share the same genetic underpinnings. We tested whether artificial correlational selection favoring specific combinations of male and female traits within families could change the strength of a very high between-sex genetic correlation for flower size in the dioecious plant Silene latifolia. This novel selection dramatically reduced the correlation in two of three selection lines in fewer than five generations. Subsequent selection only on females in a line characterized by a lower between-sex genetic correlation led to a significantly lower correlated response in males, confirming the potential evolutionary impact of the reduced correlation. Although between-sex genetic correlations can potentially constrain the evolution of sexual dimorphism, our findings reveal that these constraints come not from a simple conflict between an inflexible genetic architecture and a pattern of selection working in opposition to it, but rather a complex relationship between a changeable correlation and a form of selection that promotes it. In other words, the form of selection on males and females that leads to sexual dimorphism may also promote the genetic phenomenon that limits sexual dimorphism. K E Y W O R D S :Between-sex genetic correlation, dioecious, response to selection, sexual dimorphism.

Constraints on the coevolution of contemporary human males and females

“…The observed sexual dimorphism for our focal traits suggests that selection acting in the long term has already partially got around these constraints, as has also been demonstrated in model species [36]. Other studies suggest which other human traits may have been under sexually antagonistic selection (e.g.…”

Genotype-Phenotype Maps Maximizing Evolvability: Modularity Revisited

“…Theoretical models indicate the potential for selection on evolvability, but some authors argue that direct selection for evolvability is not feasible, or at least not necessary to explain organismal or genomic structure (Lynch 2007a, b, c;Hansen 2011). Experimental work directly addressing the evolution of the genotype-phenotype map by selection can illuminate this question, but has so far been rare (but see, e.g., Allen et al 2008;Delph et al 2011). Insight into this question can also be gained by studying the structure and evolvability of empirical genotype-phenotype maps, and by comparison to the result of this study.…”

The Evolutionary Stability of Cross-Sex, Cross-Trait Genetic Covariances

“…Sexual dimorphism is expected to arise when males and females have sex‐specific fitness optima (Lande ). Because cross‐sex genetic correlations can be weakened with relative ease in artificial selection experiments (Delph et al ), it is likely that selection can have a marked effect on cross‐sex, cross‐trait covariances, similar to the structural changes seen under selection in single‐sex estimates of G (Arnold et al ). For the population‐level estimates of the G matrix ( G mf ), we were able to detect divergence in orientation, but not size across the nine populations (Fig.…”

“…ms.). Strong antagonistic selection, with small differences in the magnitude of selection, will likely increase or maintain cross‐sex covariances (Delph et al ; J. W. McGlothlin and E. D. Brodie, unpubl. ms.).…”