Hybrid Sterility and Segregation Distortion in Drosophila pseudoobscura and Drosophila persimilis

Abstract

Speciation has occurred countless times throughout history, and yet the genetic mechanisms that lead to speciation are still missing pieces. Here, we describe the genetics of two processes that can act alone or together to cause speciation: hybrid sterility and meiotic drive. We use the Drosophila pseudoobscura/D, persimilis species as a model system to study these processes. We expanded on a prior study and saw little variation in strength of previously known hybrid sterility alleles between distinct strains of D. persimilis and the Bogota subspecies of D. pseudoobscura. Introgression of an autosomal, noninverted hybrid sterility allele from the USA subspecies of D. pseudoobscura into D. persimilis demonstrated that the D. pseudoobscura copy of a D. persimilis hybrid sterility factor also causes hybrid male sterility in a D. pseudoobscura bogotana background. This allelism suggests that the introgressed allele is ancestral, but was lost in the Bogota lineage, or that gene flow between D. pseudoobscura USA and D. persimilis moved the sterility-conferring allele from D. persimilis into D. pseudoobscura. To further understand the genetic basis of speciation, we asked if meiotic drive in D. persimilis is associated with hybrid sterility seen in D. persimilis/D. pseudoobscura hybrids. QTL mapping of both traits along the right arm of the X chromosome, where both drive and hybrid sterility loci are found, suggest that some of the causal loci overlap and may be allelic.