Ken A. Thompson. 2020. Experimental hybridization studies suggest that pleiotropic alleles commonly underlie adaptive divergence between natural populations. The American Naturalist (initially posted on 03/02/2020)
The alleles used for adaptation can pleiotropically affect traits under stabilizing selection. Thefixation of alleles with deleterious pleiotropic side-effects causes compensatory alleles to befavoured by selection. Such compensatory alleles might segregate in interpopulation hybrids,resulting in segregation variance for traits where parents have indistinguishable phenotypes. Ifadaptation typically involves pleiotropy and compensation, then the segregation variance fortraits under stabilizing selection is expected to increase with the magnitude of adaptive pheno-typic divergence between parents. This prediction has not been tested empirically, and I gath-ered data from experimental hybridization studies to evaluate it. I found that pairs of parentswhich are more phenotypically divergent beget hybrids with more segregation variance in traitsfor which the parents are statistically indistinguishable. This result suggests that adaptive di-vergence between pairs of natural populations proceeds via pleiotropy and compensation, andthat deleterious transgressive segregation variance accumulates systematically as populationsdiverge.