Fig. 4

Genetic barrier (blue) in white forsythia sampled populations (white circles) after an optimized Monmonier analysis via the Delaunay triangulation method. For reference, subsidiary mountain ranges in the map are labeled. Populations: GS-NM147 (1), GS-NM221 (2), YD-NM364 (3), YD (4), OC (5), BA-NM370a (6), BA-NM370b (7), AD (8), and YJ (9)