Fig. 1

Geographical location and genetic structure of the studied black poplar populations from the Oder valley. (a) Map showing the location of the sampled populations (pointed by red points). (b) The distribution of ΔK over K = 1-15. Proportion of the membership coefficient for each black poplar population studied and for each individual of P. nigra tree to the inferred clusters K = 2 (C,C’) and K = 4 (D,D’) from the STRUCTURE analysis