Fig
5. A visualization of realized niche dynamics, comparing the twoZiziphus species within the climatic space based on Principal
Component Analysis (PCA-env). In this two-dimensional plot, colors
signify niche characteristics, with green indicating stability, gray
representing unfilling, and yellow signifying expansion. White arrows
denote the shift in the center of the species’ niche (solid) and
describe the background conditions (dashed). The darker shading
indicates the density of species occurrences in their historical niche.
The solid line delineates the full range (100%) of climatic niche
breadths for pairs of compared species. Conversely, the dashed line
represents 50% of the environmental density, marking the boundary
climate conditions for defining the niches of Z. spina-christi(blue) and Z. nummularia (red). The results of the niche
equivalency and niche similarity tests are visually presented with
histograms showcasing the simulated overlap (gray bars) and the observed
overlap (red diamonds). Notably, the results are non-significant
(P > 0.05 ), indicating no significant difference
between the simulated and observed niche overlaps.
Bottom of FormTable 5. Pairwise niche overlap indices and niche
shift metrics.