4.4 Applicability of hypotheses for elevational patterns
The results of the discrete mid-domain effect model revealed that the alpha diversity of all the plant groups differed from those expected by the mid-domain effect hypothesis (Figure 1). Furthermore, we found no relationship between the elevational range and alpha diversity of all the plant groups, and none of the plant groups had a wider elevational range in the alpine area (Figure 4), which contradicted those expected by Rapoport’s elevational rule.
The lack of applicability of the mid-domain effect and Rapoport’s rule to elevational patterns is attributed to the simple assumptions of these hypotheses; the former excludes any effects of gradients on expected patterns (Colwell, Rahbek, & Gotelli, 2004), whereas the latter fails when species distribution is affected by the interaction of several factors including climate (Bhattarai & Vetaas, 2006; Grau, Grytnes, & Birks, 2007). Specifically, in the study area, strong winds and heavy snowfall at higher elevations increased the differences in climate between lower and higher elevations. These differences can enhance the influence of climate and the related plant-plant interactions on the elevational patterns of plants.