Environmental variables
There is unified opinion among ecologists that patterns of biodiversity
across space (i.e., latitudinal or elevational gradient) is as a result
of local adaptation to abiotic and biotic variables but not spatial
gradient per se . With the aim to detect which variables have lead
community assembly, we extracted six climatic variables (annual mean
temperature, AMT; temperature seasonality, TS; annual precipitation, AP;
precipitation seasonality, PS; net primary productivity, NPP and
potential evapotranspiration, PET), which have been frequently reported
relating to small mammals biodiversity (Wen et al. 2016b; Stevens
& Gavilanez 2015; Wu et al. 2013).
Lacking in detailed coordinate information for each sampling site and
elevational bands, data extraction for each environmental variable was
accomplished with local and regional digital elevation model (DEM). We
constructed polygon layer for each local or regional elevation band by
constraining vertical and horizontal scope. The mean values of
environmental variable within sampling site or band polygons were
extracted for each assemblage (details to see Du et al. 2017).
AMT, TS, AP and PS were all downloaded from Worldclim
(http://www.worldclim.org/) (last accessed in July, 2016) (Fick &
Hijmans 2017) at 30 seconds resolution. NPP, and PET were obtained from
MODIS products (MOD17A3 and MOD16A3) (Mu et al. 2011; Mu et
al. 2007) accessed from LP DAAC (Land Processes Distributed Active
Archive Center; https://lpdaac.usgs.gov/) (last accessed in July, 2016).
We performed layer mosaic and projection transformation with ENVI (ver.
4.7) (VIS 2011) and ArcMap (ver. 10.0) (ESRI 2010).