Sex-specific recombination landscape in a species with holocentric chromosomes

The rate and chromosomal positioning of meiotic recombination significantly affects the distribution of the genetic diversity in eukaryotic genomes. Many studies have revealed sex-specific recombination patterns, with male recombination typically biased toward chromosome ends, while female recombination is more evenly distributed along chromosomes, or concentrated in pericentromeric region. It has been proposed that such patterns in females may counteract meiotic drive caused by selfish genetic elements near centromeres and should not occur in species devoid of clearly defined centromeres, but evidence for this expectation is scarce. Here, we constructed a sex-specific genetic map of a species with holocentric chromosomes, the bulb mite ( Rhizoglyphus robini ), a model organism for sexual selection studies with heritable alternative male reproductive phenotypes. We found a similar recombination landscape in both males and females, with a consistent pattern of increased rates towards both chromosome ends, and a higher recombination rate in females than in males. Recombination rate was positively correlated with repeat density and negatively with gene density. Our results are consistent with the meiotic drive hypothesis and suggest that the evolution of recombination patterns is closely linked to chromosome features.