Expected patterns of local ancestry in a hybrid zone

Abstract

The initial drivers of reproductive isolation between species are poorly characterized. In cases where partial reproductive isolation exists, genomic patterns of variation in hybrid zones may provide clues about the barriers to gene flow which arose first during the early stages of speciation. Purifying selection against incompatible substitutions that reduce hybrid fitness has the potential to distort local patterns of ancestry relative to background patterns across the genome. The magnitude and qualitative properties of this pattern are dependent on several factors including migration history and the relative fitnesses for different combinations of incompatible alleles. We present a model which may account for these factors and highlight the potential for its use in verifying the action of natural selection on candidate loci implicated in reducing hybrid fitness.