2.4. Estimating frog population genetic divergence

To evaluate associations between alkaloid composition and evolutionary divergence between frog populations, we used the cytochrome B gene dataset of Hauswaldt et al. (2011), who sampled 197 O. pumilio individuals from 25 Central American localities. Because most sites sampled for genetic data are geographically close to sites sampled for alkaloids (Hauswaldt et al., 2011; Saporito, Donnelly, Jain, et al., 2007), we paired up alkaloid and genetic data based on Voronoi diagrams. A Voronoi diagram is a polygon whose boundaries encompass the area that is closest to a reference point relative to all other points of any other polygon (Aurenhammer, 1991). Specifically, we estimated polygons using the sites sampled for genetic data as references points. We then paired these reference points with the sites sampled for alkaloid data contained within each resulting Voronoi diagram. To estimate Voronoi diagrams, we used ArcGIS 10.3 (ESRI, Redlands). We then calculated a matrix of average uncorrected pairwise genetic distances between localities using Mega 7 (Kumar, Stecher, & Tamura, 2016). Six genetically sampled sites that had no corresponding alkaloid data were excluded from the analyses.