Little evidence for introgression between Geum rivale and Geum urbanum

We used ddRADseq in a comparative genomic context to test for introgression (gene flow between species) between two plant species that differ in mating system: Geum rivale (outcrosser) and G. urbanum (inbreeder). We obtained samples from up to 5 reference populations (3 UK, 1 Iceland, 1 Sweden) for G. rivale and 12 reference populations for G, urbanum (10 UK, 1 France, 1 Portugal). The reference populations were selected from areas where introgression was unlikely for a long period of time (>5000 years). We used the reference populations to look for signals of gene flow between the species in a broad area of sympatry, comprising 39 populations (Berwickshire, Scotland). A variety of analyses (coalescent analyses, f3 test, comparison of genetic divergence (i.e., d_xy), cluster analysis and calculation of hybrid indices based on species-specific SNPs) revealed little evidence for introgression, despite common hybridization and back-crossing to G. rivale.Double digest was performed using enzymes EcoRI and SphI