Affiliation:
1. Institute of Science and Technology Austria , Am Campus 1, 3400 Klosterneuburg , Austria
Abstract
AbstractDifferentiated X chromosomes are expected to have higher rates of adaptive divergence than autosomes, if new beneficial mutations are recessive (the “faster-X effect”), largely because these mutations are immediately exposed to selection in males. The evolution of X chromosomes after they stop recombining in males, but before they become hemizygous, has not been well explored theoretically. We use the diffusion approximation to infer substitution rates of beneficial and deleterious mutations under such a scenario. Our results show that selection is less efficient on diploid X loci than on autosomal and hemizygous X loci under a wide range of parameters. This “slower-X” effect is stronger for genes affecting primarily (or only) male fitness, and for sexually antagonistic genes. These unusual dynamics suggest that some of the peculiar features of X chromosomes, such as the differential accumulation of genes with sex-specific functions, may start arising earlier than previously appreciated.
Funder
European Research Council under the European Union’s Horizon 2020 research and innovation program
Publisher
Oxford University Press (OUP)
Subject
Genetics,Ecology, Evolution, Behavior and Systematics