Sample collection, GPS-coordinates and DNA extraction
We collected leaf and bark material in silica gel and sampled five to six localities per species in Costa Rica (2015) or Ecuador (2016, 2017; Fig. 1, Table S1). To ensure comparability between species, we sampled at least two localities in close vicinity (<12 km distance) and the other localities at larger distances (>20 km; Table S2). On average, we sampled 13 (sd 3) individuals per locality across a distance of one kilometer (Table S1). We recorded the exact location of each individual sampled to assess mating patterns within localities (Gelmi-Candusso et al. 2017) and calculated the centroid to obtain the average coordinate of each locality. We calculated Euclidean distances between localities based on these averaged coordinates in R (R Developmental Core Team 2019).
We extracted genomic DNA from ca. 60 mg of dried plant material of 424 individuals using a CTAB protocol with sorbitol washing (Barfuss et al. 2016), RNAse treatment and subsequent clean-up (gDNA Cleanup Kit, Machery-Nagl). We quantified double stranded DNA content using the Qubit 3.0 Fluorometer with the dsDNA HS Assay Kit (Thermofisher) and only used samples with more than 6 ng/µl of DNA.