Dispersal, niche, and isolation processes jointly explain species turnover patterns of nonvolant small mammals in a large mountainous region of China

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.

Abundance of small mammals correlates with their elevational range sizes and elevational distributions in the subtropics

“…The similarity across the Gongga, Baima Snow and Sejila mountains is notable given the shared geological and mammalian faunal histories. The isolation was particularly strong at the high and middle elevations, facilitating the emergence of endemic non-flying small mammals (Wen et al 2016a). It gave rise to numerous high, island-like mountains (most  3000 m, including our study areas) spatially isolated from one another by deep valleys, among which diversification and speciation occurred (He and Jiang 2014).…”

“…The mountains of the MRSC harbored abundant climatically stable habitats during Pleistocene climatic oscillations (glacial-interglacial variations) (Qu et al 2014, Wen et al 2016b, Wu et al 2017. endemic or early colonizing species negatively impacts the subsequently colonizing species by reducing the availability of space and recourses, Chase 2003) plays a role in the assembly of montane small mammal communities (Wen et al 2016a), endemic species may gain a competitive advantage over non-endemic counterparts and therefore become more abundant. By comparison, although non-endemic species usually show wider distribution and occur in diverse habitats in subtropical regions (Walter 1971), they may not be able to establish a large-sized population in a mountainous region with unique high topographical complexity and ecological heterogeneity.…”

“…Although mountain shapes are diverse (Elsen andTingley 2015, Körner et al 2017), there is a generally positive trend of geographical isolation with increasing elevation (Steinbauer et al 2016), affecting both species diversity patterns (Brown 2001, Wen et al 2016a) and composition of montane assemblages. Steinbauer et al (2016) recently discovered a global pattern of monotonic increase in the percentage of endemic plant species with increasing elevation, mainly explained by topography-drive isolation.…”

Diversity and distribution of parasitic angiosperms in China

“…From east to west, Chinese topography is characterized by terrain, ranging from plains in the eastern provinces (>500 m at altitude) to basins in the middle ones (1,000–2,000 m at altitude), to the Qinghai‐Tibet Plateau in the west provinces (above 4,000 m at altitude; ECCPG, ). Such a climate and geographic diversity may result in a wide range of habitats and facilitate local species differentiation, giving rise to endemism (Huang, Ma, & Huang, ; Wen et al., ). For example, the high species richness of the genus Pedicularis (including 441 herbaceous species and 89 subspecies or variants) in China (Wu et al., 1994–2012) has been frequently attributed to the extremely high topographic heterogeneity, mainly resulting from the uplift of the Tibetan Plateau, in the southwest mountainous areas (Zhao et al., ).…”

“…(1,000-2,000 m at altitude), to the Qinghai-Tibet Plateau in the west provinces (above 4,000 m at altitude; ECCPG, 1985b). Such a climate and geographic diversity may result in a wide range of habitats and facilitate local species differentiation, giving rise to endemism (Huang, Ma, & Huang, 2017;Wen et al, 2016). For example, the high species richness of the genus Pedicularis (including 441 herbaceous species F I G U R E 1 Distribution of species richness (a) and area-corrected species richness (b) of parasitic plants in 28 provinces of China and 89 subspecies or variants) in China (Wu et al, 1994(Wu et al, -2012 has been frequently attributed to the extremely high topographic heterogeneity, mainly resulting from the uplift of the Tibetan Plateau, in the southwest mountainous areas .…”