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

Abstract

The idea that a positive abundance-range size relationship (ARR) is pervasive in nature has been challenged by recent studies focused on montane and island vertebrate assemblages. However, because some of these studies used species' local abundance and regional or global range size in examining the ARRs, the negative and neutral trends reported are questionable. Here, by relating species' mean abundance along elevational gradients to elevational range size, we examined the ARRs of non-flying small mammals on three subtropical mountains of southwest China. We also examined the relationship between mean abundance and elevational range centre (reflecting species' elevational distribution) on each mountain, and compared the elevational range centre and mean abundance between endemic and non-endemic species as they may have been subjected to different intensities of historical (e.g. geographical isolation and colonization) and ecological (e.g. ecological specialization) processes. The results show significantly positive relationship between mean abundance and elevational range size on each mountain. We also observed a consistent positive relationship between mean abundance and elevational range centre, probably due to the stronger local specialization of mid-and high-elevation species, lower species richness at higher elevations, and increasing extinction rate of small-ranged less abundant species towards higher elevations. A novel finding of our study is that endemic species show higher elevational range centres and higher mean abundance than non-endemic species on each mountain, which is most likely driven by the increasing geographical isolation with elevation and the higher degree of ecological specialization for endemic species. Measuring abundance and range size at the same spatial scale is a key prerequisite to evaluate the ARRs of montane small mammals.

Elevation patterns and critical environmental drivers of the taxonomic, functional, and phylogenetic diversity of small mammals in a karst mountain area

“…In this study, we deconstructed the biodiversity gradient by taxonomic group and distribution range scale and assessed the drivers of biodiversity in the Wuling Mountains. In general, the elevation patterns of TD for all small mammal groups (all, Rodentia, Eulipotyphla, broad‐range and narrow‐range species) were hump‐shaped, consistent with the findings of most previous elevation diversity studies of small mammals (Hu et al., 2017; Rowe, 2009; Shuai, Ren, Yan, Song, & Zeng, 2017; Wen et al., 2018). Hump‐shaped patterns seem to be the dominant patterns along mountain slopes.…”

Varying support for abundance‐centre and congeneric‐competition hypotheses along elevational transects of mammals

“…the midpoint between observed upper and lower range limits) should be highly consistent with the elevation site where the species had the highest relative abundance (i.e. abundance‐weighted range centre; Menéndez et al., 2014; Wen, Wu, et al., 2018). To test this prediction, we calculated the species abundance‐weighted range centre:where m.n represent the elevation sites occupied by species a , E i represents the elevation (m) of elevational site i , and P ai represents the ratio of individuals of species a collected at site i to the total number of its individuals collected across the elevational gradient.…”

Divergent selection along elevational gradients promotes genetic and phenotypic disparities among small mammal populations

“…Surprisingly, we found a positive correlation between size and predation risk in most cases (Table ). This relationship might be an indirect response to reduced prey species abundance at lower altitudes (Fu et al, ; Wen et al, ), which leads to relaxed competition for food (Heaney, ). Notably, our conclusions are derived from a coarse‐grained approach using species' ranges to predict local predator richness.…”

“…Detailed descriptions of the sampling protocols can be found in Wu et al (2013) and Wen et al (2018). This unique database includes specimens of small mammals systematically collected from several mountains in China.…”