3.2. Climate niche divergence/conservatism
The initial two axes of PCA accounted for 45.44% and 23.16% of the total variance, respectively. The climate niche overlap between the two species was relatively low, with Schoener’s D value being 0.30. Notably, the outcomes of the niche equivalency test, as depicted in Fig. 5, revealed that the actual overlap value was significantly higher (Schoener’s D) compared to the simulated niche (P < 0.009 ). This suggests that the similarity in climate niches between the two species is more pronounced than what would be expected by random chance. Furthermore, as per the niche similarity test, the observed niche overlap did not exhibit a significant increase compared to what would be anticipated based on the environmental conditions available to each species in both directions (P (1->2) < 0.07, P (2->1) < 0.06 ). When calculating climatic niche dynamic indices, which indicate niche shifts in similar conditions, it becomes evident that there is a high degree of niche stability at 96%. Additionally, the degree of niche unfilling stands at a moderate 43%, while niche expansion is notably low at 3%.
A comprehensive analysis of climatic niche quantitative tests underscores that Z. spina-christi and Z. nummulariaexhibit limited overlap (Schoener’s D = 30%) (Broennimann et al., 2012; Ahmad et al., 2019; Datta et al., 2019; Xian et al., 2023) (as illustrated in Fig. 5 and detailed in Table 5).