Abstract
Understanding the mechanisms that govern the spatial patterns of species turnover (beta diversity) has been one of the fundamental issues in biogeography. Species turnover is generally recognized as strong in mountainous regions, but the way in which different processes (dispersal, niche, and isolation) have shaped the spatial turnover patterns in mountainous regions remains largely unexplored. Here, we explore the directional and elevational patterns of species turnover for nonvolant small mammals in the Hengduan Mountains of southwest China and distinguish the relative roles of geographic distance, environmental distance, and geographic isolation on the patterns. The spatial turnover was assessed using the halving distance (km), which was the geographic distance that halved the similarity (Jaccard similarity) from its initial value. The halving distance was calculated for the linear, logarithmic, and exponential regression models between Jaccard similarity and geographic distance. We found that the east-west turnover is generally faster than the south-north turnover for high-latitudinal regions in the Hengduan Mountains and that this pattern corresponds to the geographic structure of the major mountain ranges and rivers that mainly extend in a south-north direction. There is an increasing trend of turnover toward the higher-elevation zones. Most of the variation in the Jaccard similarity could be explained by the pure effect of geographic distance and the joint effects of geographic distance, environmental distance, and average elevation difference. Our study indicates that dispersal, niche, and isolation processes are all important determinants of the spatial turnover patterns of nonvolant small mammals in the Hengduan Mountains. The spatial configuration of the landscape and geographic isolation can strongly influence the rate of species turnover in mountainous regions at multiple spatial scales.
Highlights
One central goal in biogeography is to understand the patterns and underlying causes of the variation in species diversity at multiple spatial scales (MacArthur 1972)
This study aimed to (1) distinguish the relative effects of geographic distance, environmental distance, and geographic isolation on the species turnover patterns of nonvolant small mammals in the Hengduan Mountains; (2) explore whether the spatial configuration of the landscape controls the spatial turnover in mountainous regions; and (3) determine whether the increasing geographic isolation with elevation would cause any elevational patterns of species turnover in mountainous regions
The directional turnover patterns generally fit the geographic structure of the region and suggest that the spatial configuration of the landscape can strongly influence the spatial turnover in mountainous regions
Summary
One central goal in biogeography is to understand the patterns and underlying causes of the variation in species diversity at multiple spatial scales (MacArthur 1972). Beta diversity (i.e., species turnover) has been one of the core areas in ecological research over the past decade, but species turnover patterns and their underlying processes at different spatial scales are still not fully explored (Veech and Crist 2007; Anderson et al.2011). The most commonly reported pattern in species turnover is the decay of community similarity with increasing geographic distance, a phenomenon that has been frequently explained by two mechanisms: dispersal limitation and niche limitation (Soininen et al 2007; Wen et al 2014).
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