16 Oral - James F. Crow Early Career Researcher Award Finalist Talks
Wednesday June 08, 1:40 PM - 2:05 PM

Authors:
Ailene MacPherson ^1,2,7; Silu Wang ^2,3,4; Ryo Yamaguchi ^5,6; Loren Rieseberg ²; Sarah (Sally) Otto ²

Affiliations:
1) Simon Fraser University; 2) University of British Columbia; 3) University of California Davis; 4) University of California Berkeley; 5) Tokyo Metropolitan University; 6) Hokkaido University; 7) University of Toronto

Keywords:
Speciation & hybridization

Population genomic analysis of hybrid zones is instrumental to our understanding of the evolution of reproductive isolation. Many temperate hybrid zones are formed by the secondary contact between two parental populations that have undergone post-glacial range expansion. In this work, we showed that explicitly accounting for historical parental isolation followed by range expansion prior to secondary contact is fundamental for explaining genetic and fitness patterns in these hybrid zones. Specifically, ancestral population expansion can result in allele surfing where neutral or slightly deleterious mutations drift to the high frequency at the expansion front. If these surfed deleterious alleles are recessive, they can contribute to substantial heterosis in hybrids produced at secondary contact, counteracting negative effects of Bateson-Dobzhansky-Muller incompatibilities (BDMIs) hence weakening reproductive isolation. When BDMIs are linked to such recessive deleterious alleles the fitness benefit of introgression at these loci can facilitate introgression at the BDMIs. The extent to which this occurs depends on the strength of selection against the linked deleterious alleles and the distribution of recombination across the chromosome. Finally, surfing of neutral loci can alter the expected pattern of population ancestry, thus accounting for historical population expansion is necessary to develop accurate null genomic models of secondary-contact hybrid zones.