Figure 2.

Five selected scenarios of niche change observed in the study species and associated expansion (red), stability (blue) and unfilling (green) in the alien niche. Darker shading indicates higher density of occurrences of the species; solid contour lines, 100% of available environment; dashed contour lines, 50% of most common background environment. Arrows link the centroids (optimal niche position) of the native and alien distributions (continuous arrow) and link native and alien extents (dashed arrow). (1) Scenario A: Erigeron annuus, change of niche position, niche contraction and unfilling in the alien niche. (2) Scenario B: Mikania micrantha, change in niche optimum during invasion but no significant alteration of niche breadth, niche unfilling. (3) Scenario C: Euphorbia esula, significant change in niche position and broadening, expansion into novel niche space. (4) Scenario D: Miconia calvescens, niche optima did not change but niches significantly contracted during invasion, leading to unfilling. (5) Scenarios A and C: Cortaderia selloana, significant change in niche optimum and both niche broadening (PC1) and niche contraction (PC2) occurred.