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.