Leaf shape morphology often differs among species which may be due to adaptations to particular environmental conditions. Mimulus laciniatus, a species of monkey flower, is known for adaptations to harsher rocky outcrops in comparison to the closely related M. guttatus. Due to ongoing gene flow and diverging selection forces, many of the morphological differences can be explained by many tightly linked loci or few large-effect pleiotropic quantitative trait loci (QTLs). This study aims to identify the QTLs that regulate leaf length, petiole length, leaf width, leaf area, leaf perimeter, and boundary layer temperature. In a common garden experiment, M. guttatus and M. laciniatus were crossed to produce an F2 population for trait and genetic analysis. Observed traits were measured in comparison to each other as well as analyzed for heritability and moderate to large-affect genomic areas containing QTLs. This study finds that divergence between leaf shape morphology is due to few pleiotropic QTLs of large effect. Additionally, there was significant overlap with a previous study conducted by Ferris et al. (2017) utilizing the same genomic data set but analyzing flowering traits and leaf concavity. This study supports the theory that adaptive traits and traits leading to reproductive isolation in sympatric populations experiencing ongoing gene-flow will be regulated by few areas of closely linked, pleiotropic, and large effect QTLs.
