Based on a comprehensive set of species records, the realized climatic niche space of the native populations was much larger than the niche space occupied by the expanding populations and those whose status could not be determined (Volume BWD Native = 3172.6; Volume BWD Expanding = 19.7; Volume BWD Unknown = 5.3; Volume MMCP Native = 722.3; Volume MMCP Expanding = 236.2; Volume MMCP Unknown = 108.2). For visualization, see Fig. 4 and Supplementary Material S4. The shared volumes between native and expanding populations were comparatively small (Intersection BWD Native / Expanding = 57.0; Intersection MMCP Native / Expanding = 6.4) leading to low–very low Soerensen indices (S BWD Native / Expanding = 0.12; S MMCP Native / Expanding = 0.004). This indicates a strong niche shift between native and expanding populations, wherein the combination of PC1 and PC3 had the highest contribution to the differentiation (Fig. 4).