Genetic architecture of traits associated with reproductive barriers in Silene: coupling, sex chromosomes and variation

The evolution of reproductive barriers and their underlying genetic architecture is of central importance for the formation of new species. Reproductive barriers can be controlled either by few large-effect loci suggesting strong selection on key traits, or by many small-effect loci, consistent with gradual divergence or with selection on polygenic or multiple traits. Genetic coupling between reproductive barrier loci further promotes divergence, particularly divergence with ongoing gene flow. In this study, we investigated the genetic architectures of ten morphological, phenological and life history traits associated with reproductive barriers between the hybridizing sister species Silene dioica and S. latifolia; both are dioecious with XY sex determination. We used quantitative trait locus (QTL) mapping in two reciprocal F2 crosses. One to six QTLs per trait, including 9 major QTLs (PVE > 20%) were detected, in total, on 11 of 12 linkage groups. We found strong evidence for couplin...