Plants pose a well-known challenge to the biological species concept because hybridization is a common occurrence. Range dynamics have a crucial role in determining whether species are given the opportunity to interbreed or not. Successful hybridization can be of particular concern when considering rangelimited species and their persistence. In my thesis research, I examine the apparent hybrid zone between the southern Oregon endemic Ranunculus austrooreganus, a candidate threatened species due

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... to its limited range, and its widespread congener, Ranunculus occidentalis, whose range spans from California to Alaska. The discovered contact zone was recognized in populations which contained apparent intermediate ventral petal coloration phenotypes. First, I utilized morphological quantification to understand phenotypic variation. Phenotype quantification based on ventral petal coloration and leaf trichome density have confirmed the presence of intermediate populations. Second, I confirmed extensive introgression through nuclear genome surveys with Genotyping-by-Sequencing despite structure analyses indicating the presence of two genetic subgroups. Third, 50 outlier loci were analyzed across geographic clines where results suggest the width of the hybrid zone spans 20km. Sampled populations of R. austro-oreganus and R. occidentalis display evidence of ii extensive, ongoing gene flow and this species complex provides a unique example of genetic exchange between variable phenotypes. iii