Homozygosity at its Limit: Inbreeding Depression in WildArabidopsis arenosaPopulations

AbstractNew combinations of genetic material brought together through hybridization can lead to unfit offspring as a result of outbreeding or inbreeding depression. In selfing plants such asArabidopsis thaliana, outbreeding depression is typically the result of pairwise deleterious epistatic interactions between two alleles that can geographically co-occur. What remains elusive is how often alleles resulting in genetic incompatibilities co-occur in natural populations of outcrossing plant species. To address this question, we screened over two thousand five hundred wildArabidopsis arenosahybrid plants in search for potential genetic mismatches. We show that although abnormal deleterious phenotypes are common, the transcriptional profiles of these abnormalA. arenosaplants differ substantially from those seen in incompatibleA. thalianahybrids. The abnormal hybrid phenotypes inA. arenosahad different underlying genetic architectures, yet a repeated theme was increased homozygosity, indicating that inbreeding rather than outbreeding depression gives rise to some of the deleterious phenotypes segregating in wildA. arenosapopulations.