Adaptive divergence of meiotic recombination rate in ecological speciation

Abstract

AbstractTheories predict that directional selection during adaptation to a novel habitat results in elevated meiotic recombination rate. Yet the lack of population-level recombination rate data leaves this hypothesis untested in natural populations. Here we examine the population-level recombination rate variation in two incipient ecological species, the microcrustaceanDaphnia pulex(an ephemeral-pond species) andD. pulicaria(a permanent-lake species). The divergence ofD. pulicariafromD. pulexinvolved habitat shifts from pond to lake habitats as well as strong local adaptation due to directional selection. Using a novel single-sperm genotyping approach, we estimated the male-specific recombination rate of two linkage groups in multiple populations of each species in common garden experiments and identified a significantly elevated recombination rate inD. pulicaria. Most importantly, population genetic analyses show that the divergence in recombination rate between these two species is most likely due to divergent selection in distinct ecological habitats rather than neutral evolution.Significance statementWhether directional selection during adaptation to a novel habitat results in elevated meiotic recombination remains largely untested in natural populations. This work examines the population-level recombination rate in two closely related microcructacean speciesDaphnia pulexandD. pulicariausing single-sperm genotyping approach. Recombination rate data from two linkage groups show elevated recombination rates inD. pulicariawhose divergence fromD. pulexis accompanied by a habitat shift. Importantly, population genetic analysis suggests that this divergence of recombination is likely adaptive rather than neutral.