title: The Relative Contributions of theXChromosome and Autosomes to Local Adaptation.
abstract: Models of sex chromosome and autosome evolution yield key predictions about the genomic basis of adaptive divergence, and such models have been important in guiding empirical research in comparative genomics and studies of speciation. In addition to the adaptive differentiation that occurs between species over time, selection also favors genetic divergence across geographic space, with subpopulations of single species evolving conspicuous differences in traits involved in adaptation to local environmental conditions. The potential contribution of sex chromosomes (theXorZ) to local adaptation remains unclear, as we currently lack theory that directly links spatial variation in selection to local adaptation ofX-linked and autosomal genes. Here, we develop population genetic models that explicitly consider the effects of genetic dominance, effective population size, and sex-specific migration and selection on the relative contributions ofX-linked and autosomal genes to local adaptation. We show thatX-linked genes should nearly always disproportionately contribute to local adaptation in the presence of gene flow. We also show that considerations of dominance and effective population size-which play pivotal roles in the theory of faster-Xadaptation between species-have surprisingly little influence on the relative contribution of theXchromosome to local adaptation. Instead, sex-biased migration is the primary mediator of the strength of spatial large-Xeffects. Our results yield novel predictions about the role of sex chromosomes in local adaptation. We outline empirical approaches in evolutionary quantitative genetics and genomics that could build upon this new theory.
authors.affiliation: School of Biological Sciences, Monash University, Clayton 3800, Australia.
authors.forename: Clémentine
authors.initials: C
authors.lastname: Lasne
authors.affiliation: School of Biological Sciences, Monash University, Clayton 3800, Australia.
authors.forename: Carla M
authors.initials: CM
authors.lastname: Sgrò
authors.affiliation: School of Biological Sciences, Monash University, Clayton 3800, Australia tim.connallon@monash.edu.
authors.forename: Tim
authors.initials: T
authors.lastname: Connallon
mesh_terms: D000222:Adaptation, Physiological; D025041:Animal Migration; D000818:Animals; D019143:Evolution, Molecular; D005260:Female; D051456:Gene Flow; D008297:Male; D008957:Models, Genetic; D014960:X Chromosome / Q000235:genetics*
keywords: adaptation; cline; dominance; effective population size; sex linkage