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

1 February 2018

Wen, Zhixin; Wu, Yongjie; Cheng, Jilong; Cai, Tianlong; Du, Yuanbao; Ge, Deyan; Xia, Lin; Yang, Qisen

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.