article published yes Sean Stankowski author 43161670-5719-11EA-8025-FABC3DDC885E Madeline A. Chase author Hanna McIntosh author Matthew A. Streisfeld author NiBa department Understanding the phenotypic and genetic architecture of reproductive isolation is a long‐standing 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 modelling 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<jats:italic>Mimulus aurantiacus</jats:italic>. Several candidate isolating traits and anonymous single nucleotide polymorphism 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 genome. Using a novel, geographic cline‐based genome scan, we demonstrate that candidate barrier loci are broadly distributed across the genome, rather than mapping to one or a few “islands of speciation.” Quantitative trait locus (QTL) mapping reveals that most floral traits are highly polygenic, with little evidence that QTL colocalize, indicating that most traits are genetically independent. Finally, we find little evidence that QTL and candidate barrier loci overlap, suggesting that some loci contribute to other forms of reproductive isolation. Our findings highlight the challenges of understanding the genetic architecture of reproductive isolation and reveal that barriers to gene flow other than pollinator isolation may play an important role in this system. Wiley2023 eng GeneticsEcologyEvolutionBehavior and Systematics 0962-1083 1365-294X 36651268 00091924460000110.1111/mec.16849 3282041-2054 S. Stankowski, M.A. Chase, H. McIntosh, M.A. Streisfeld, Molecular Ecology 32 (2023) 2041–2054. Stankowski S, Chase MA, McIntosh H, Streisfeld MA. 2023. Integrating top‐down and bottom‐up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone. Molecular Ecology. 32(8), 2041–2054. S. Stankowski, M. A. Chase, H. McIntosh, and M. A. Streisfeld, “Integrating top‐down and bottom‐up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone,” <i>Molecular Ecology</i>, vol. 32, no. 8. Wiley, pp. 2041–2054, 2023. Stankowski, S., Chase, M. A., McIntosh, H., &#38; Streisfeld, M. A. (2023). Integrating top‐down and bottom‐up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone. <i>Molecular Ecology</i>. Wiley. <a href="https://doi.org/10.1111/mec.16849">https://doi.org/10.1111/mec.16849</a> Stankowski, Sean, et al. “Integrating Top‐down and Bottom‐up Approaches to Understand the Genetic Architecture of Speciation across a Monkeyflower Hybrid Zone.” <i>Molecular Ecology</i>, vol. 32, no. 8, Wiley, 2023, pp. 2041–54, doi:<a href="https://doi.org/10.1111/mec.16849">10.1111/mec.16849</a>. Stankowski S, Chase MA, McIntosh H, Streisfeld MA. Integrating top‐down and bottom‐up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone. <i>Molecular Ecology</i>. 2023;32(8):2041-2054. doi:<a href="https://doi.org/10.1111/mec.16849">10.1111/mec.16849</a> Stankowski, Sean, Madeline A. Chase, Hanna McIntosh, and Matthew A. Streisfeld. “Integrating Top‐down and Bottom‐up Approaches to Understand the Genetic Architecture of Speciation across a Monkeyflower Hybrid Zone.” <i>Molecular Ecology</i>. Wiley, 2023. <a href="https://doi.org/10.1111/mec.16849">https://doi.org/10.1111/mec.16849</a>. 147872024-01-10T10:44:45Z2024-01-16T10:10:00Z