Fig. 1

Location of the study area and reference samples, proportion of each species sampled in each population of Ticino, and individual ancestry to the P. lessonae (green/grey) and P. ridibundus (red) gene pools, as inferred by STRUCTURE with k = 2–4 (based on 2521 SNPs). The hybrid frogs P. kl. esculentus accordingly received intermediate ancestry values. Three P. lessonae gene pools were identified, including two in Ticino. The distributions of P. lessonae (plain green) and P. kl. esculentus (dashed lines) are shown on the map, based on the IUCN red list data. Photo: P. kl. esculentus from AGR (diploid all-hybrid population); photo and map credit: C. Dufresnes