Genetics of incipient speciation in Drosophila mojavensis. III. Life history divergence in allopatry and reproductive isolation

We carried out a three-tiered genetic analysis of egg-to-adult development time and viability in ancestral and derived populations of cactophilic D. mojavensis to test the hypothesis that evolution of these life history characters has shaped premating reproductive isolation in this species. First, a common garden experiment with 11 populations from Baja California and mainland Mexico and Arizona reared on two host cacti revealed significant host plant X region and population interactions for viability and development time. Second, replicated line crosses with cactus-reared flies revealed autosomal, X chromosome, cytoplasmic, and autosome X cactus influences on development time. Third, a QTL analysis of development time differences on 1688 Baja X mainland F2 males revealed eight QTL. Eight GxE interactions were also detected, caused by longer development times associated with mainland alleles reared a mainland host with smaller differences among Baja genotypes on a Baja host plant. ...