Integrating top-down and bottom-up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone

Understanding the phenotypic and genetic architecture of reproductive isolation is a longstanding goal of speciation research. In several systems, large-effect loci contributing to barrier phenotypes have been characterized, but such causal connections are rarely known for more complex genetic architectures. In this study, we combine ‘top-down’ and ‘bottom-up’ approaches with demographic modeling toward an integrated understanding of speciation across a monkeyflower hybrid zone. Previous work suggests that pollinator visitation acts as a primary barrier to gene flow between two divergent red- and yellow-flowered ecotypes of Mimulus aurantiacus. Several candidate isolating traits and anonymous SNP loci under divergent selection have been identified, but their genomic positions remain unknown. Here, we report findings from demographic analyses that indicate this hybrid zone formed by secondary contact, but that subsequent gene flow was restricted by widespread barrier loci across the geno..., ,