Meeting Abstract
In several hybrid zones between species with male-dominant mating systems, male aggression drives genetic introgression into the less aggressive species. Sex-role-reversed systems, in which females compete for access to mates, provide a unique opportunity to investigate hybridization from a female perspective. We employ a hybrid zone between two sex-role reversed shorebird species, Jacana spinosa and Jacana jacana, to examine the role of female competition in hybridization. In a previous study, mitochondrial DNA (mtDNA) sequences revealed an asymmetry of introgression – hybrids share their mtDNA haplotypes with J. spinosa, but not J. jacana. Geographic clinal analyses suggested that mtDNA haplotypes show reduced introgression relative to autosomal markers, a pattern typically interpreted as an indication of Haldane’s Rule, i.e. reduced fitness in the heterogametic sex, which are females in birds. Aggression assays revealed that J. spinosa females are more aggressive than J. jacana females, which could allow them to outcompete J. spinosa females for territories in the hybrid zone. In this study, we investigate whether asymmetrical introgression is related to the competitive dominance of J. spinosa females, or a consequence of hybrid inviability. To test for female-mediated asymmetric introgression across the hybrid zone, we conducted geographic cline analyses comparing a sub-genomic dataset of ~43,000 SNPS with traits related to the female competitive phenotype. We find that the behavioral processes mediating hybridization between sex-role reversed species are similar to those with dominant-male sex roles, but that role-reversed females may face higher postzygotic selection pressures than traditional-role males in the context of avian hybridization.
