Fig. 2

Results of STRUCTURE analyses performed with the six Portuguese P. nigra populations (a, b) and/or the foreign P. nigra samples belonging to different subspecies (c, d). a, c Proportion of the membership coefficient for each individual for the inferred clusters when K = 2, according to STRUCTURE results. Each individual is represented by a thin vertical line, which is partitioned into coloured segments that indicate the individual’s estimated membership fraction in K = 2 clusters. Different populations are separated by vertical lines. b, d Plot of the delta K value, calculated according to Evanno et al. (2005) and plotted against the number of the modelled clusters