Species community assembly change with different spatial scales
Beetles β-diversity between sampling unites was significantly lower at each successive spatial scale (i.e., as the spatial distance between sampled FITs increased) (KW chi-square = 797.10, df = 4, P< 0.001, Fig. 2-I) than that of the tree except at the second narrowest scales, i.e., β2 (Fig. 2-I). The general pattern of tree species turnover between sampling squares was similar to that of the beetles (KW chi-square = 956.20, df = 4, P< 0.001, Fig. 2-I). For the beetles group, the largest increase in β-diversity was evident between the plot (i.e., β2: 200-300 m apart) and transect (β3: 1-3 km apart) scale (Fig. 2-I) and these two scales had no significant difference with each other (P > 0.05). However, the largest increase inβ-diversity for the tree group was only evident at the transect (β3: 1-3 km apart) scale (Fig. 2-I). The Wilcoxon paired t -tests showed that tree communities had a significantly higher β-diversity value than beetles at the scales of β1, β3, and δ1 (Z = 3.732, 6.275, and 10.35, respectively; P < 0.001), but significantly lower β-diversity value at the scale of β2(Z = 6.275; P < 0.001) (Fig. 2-I). Thus, trees and beetle compositional turnover showed a roughly similar trend with some small differences along the increased spatial distance.
At the regional scale, tree and beetle β-diversity showed an asynchronous decreasing pattern from the tropical to subtropical and cold temperate regions (Fig. 2-II). For both the tree and beetle groups, the β-diversity among the three regions had significant differences (trees: KW chi-square = 11.5, df = 2, P < 0.01; beetles: KW chi-square = 15.2, df = 2, P < 0.001) (Fig. 2-II). The Wilcoxon paired t -tests showed that the tree community β-diversity was significantly higher than that of beetles at all three regions (Z = Bubeng:7.364, Ailaoshan:8.783, Lijiang:6.108;P < 0.001) (Fig. 2-II). Furthermore, at the transect scale of each region, the β-diversity of both the tree and beetle groups showed a generally decreasing pattern with increasing elevation (trees: KW chi-square = 56.4, df = 8, P < 0.001; beetles: KW chi-square = 69.5, df = 8, P < 0.001) (Fig. 2-III). However, the pairwise comparison of β-diversity between the tree and beetle groups at each transect did not show a significant difference between each other (P > 0.05) (Fig. 2-III) except for all comparisons in the subtropical Yulong mountain and transects of 800 and 1000 m in tropical Bubeng.