Fig. 1

Population structure and phylogenetic analysis. a Population structure and phylogeny of 113 individuals of Juglans regia and J. sigillata from throughout both species’ ranges. Individuals in the structure plot are ordered according to their phylogenetic proximity. Red branches and bars represent the western group of J. regia, orange branches and bars the eastern group, blue branches and bars J. sigillata, black branches represent hybrids between eastern J. regia and J. sigillata, and cyan branches hybrids between western and eastern J. regia. Values at nodes represent bootstrap support. b A principal component analysis (PCA) of 113 individuals of J. regia and J. sigillata. Blue crosses represent J. sigillata, orange triangles eastern J. regia, red pluses western J. regia, and black circles admixed individuals. c Proportions of SNPs in the western or eastern group of J. regia shared with the nine admixed individuals.d Proportions of private SNPs in nine individuals of eastern, western, and admixed J. regia. The boxplots indicate the minimum (the lower hinge), maximum (the upper hinge), and median (the middle hinge). NS. means no significant difference, “***” p < 0.001, “**” p < 0.01, “*” p < 0.05