Why Evolution Keeps Genetic Diversity Alive in Competing Sexes
Researchers discovered that when males and females face conflicting evolutionary pressures, populations retain far more genetic variation than previously predicted. The finding resolves a decades-old puzzle in biology and could reshape how scientists predict trait inheritance in agriculture, conservation, and medical genetics.
Originaltitel: Sexually antagonistic selection maintains genetic variance when sexual dimorphism evolves
<p>Genetic variance (<em>V<sub>G</sub></em>) in fitness related traits is often unexpectedly high, evoking the question how <em>V<sub>G</sub></em> can be maintained in the face of selection. Sexually antagonistic (SA) selection favouring alternative alleles in the sexes is common and predicted to maintain <em>V<sub>G</sub></em>, while directional selection should erode it. Both SA and sex-limited directional selection can lead to sex-specific adaptations but how each affect <em>V<sub>G</sub></em> when sexual dimorphism evolves remain experimentally untested. Using replicated artificial selection on the seed beetle <em>Callosobruchus maculatus</em> body size we recently demonstrated an increase in size dimorphism under SA and male-limited (ML) selection by 50% and 32%, respectively. Here we test their consequences on genetic variation. We show that SA selection maintained significantly more ancestral, autosomal additive genetic variance than ML selection, while both eroded sex-linked additive variation equally. Ancestral female-specific dominance variance was completely lost under ML, while SA selection consistently sustained it. Further, both forms of selection preserved a high genetic correlation between the sexes (<em>r<sub>m,f</sub></em>). These results demonstrate the potential for sexual antagonism to maintain more genetic variance while fueling sex-specific adaptation in a short evolutionary timescale, and are in line with predicted importance of sex-specific dominance reducing sexual conflict over alternative alleles.</p>