Altitudinal Gradient May Shadow the Effects of Altitudinal Range on Species Diversity

Abstract

Altitudinal range is widely used as a proxy of habitat heterogeneity to explain broad-scale geographical patterns of species diversity. Though altitudinal range is a factors derived from altitudinal gradient, altitudinal range’s effects on species diversity on altitudinal gradient remain little known. Based on large scale information of plant species, climatic and geographical factors, we investigated the altitudinal patterns of plant species diversity in the East Himalaya regions, and the effects of altitudinal range on species diversity on altitudinal gradient. We constructed two coefficients, ARDMA (altitudinal range divided by median altitude) and SDDAR (species diversity divided by altitudinal range). We used Spearman’s rank correlation to examine the associations among all of factors. Our results showed that species diversity decreased as the increase of altitude, and significantly related to potential evaporation. No significant correlation was observed between altitudinal range and species diversity, whereas ARDMA significantly related to species diversity, suggesting that only when altitudinal gradient was controlled, were there significant correlations between altitudinal range and species diversity. SDDAR significantly and negatively related to median altitude. We concluded that energy availability significantly affected the altitudinal patterns of species diversity, and altitudinal gradient may shadow the effects of altitudinal range on species diversity.