A novel sex-associated genomic region in Catostomus fish species.

Abstract

Genomic regions that influence sex are hypothesized to play a key role in evolutionary di- versification, as sex determination mechanisms may promote or impede reproductive isolation between closely related species. Remarkably, these mechanisms are almost completely un- known in many taxa, especially in clades like fish with extremely variable sex determination. In Catostomus fishes, contemporary hybridization is extensive but variable, and factors influ- encing hybridization dynamics are not fully understood. We used genotyping-by-sequencing data from three Catostomus species (bluehead, white, and flannelmouth suckers) to identify regions of the genome associated with sex using a genome-wide association study. We identi- fied a genomic region in bluehead suckers from Colorado on chromosome 4 that significantly associates with sex and is suggestive of a sex-determining region. This region is not signifi- cant in the other species studied here, or in a divergent lineage of bluehead suckers, implying that either the sex-determining region of the genome differs in these species and populations, or that technical limitations precluded identification of sex determination. These results pro- vide the first description of sex-determination systems in Catostomus species, and suggest that further investigation of sex determination in the Catostomidae are needed to better characterize evolutionary turnover of sex determination in this species-rich group.