1.5 Data analysis
1.5.1 Analysis of NTF species composition and distribution
The occurrence frequency (OF) for each species and sampling site was
calculated respectively. OF (%) was calculated as: (number of specimens
with NTF occurrence / total number of specimens) × 100%. Species with
OF > 5% were defined as widespread species, while species
with OF < 1% were defined as rare species.
Using the latitude and longitude of each site and NTF OFs, we then
plotted distribution maps based on genus, species, and rare species with
the raster , sf and ggplot2 packages in R version
4.02.
The mean variance ratio was used for evaluating NTF species
distributions. A mean variance ratio of 1 indicated a random
distribution (conforming to the Poisson’s distribution); a mean variance
ratio >1 indicated a clustered distribution; a mean
variance ratio <1, indicated an even distribution. The
significance of these distributions was verified using a T-test.
We divided sampling areas into 9 grids using QGIS version 3.10. We
selected the six grids with the largest sampling areas (grids A, B, C,
D, E and F) for analysis (Figure S1 a). The watershed boundaries of
Yunnan Province were extracted from a derived digital elevation model
(CGIAR-CSI SRTM v4.1) at 90-meters resolution using GIS geoprocessing
algorithms (Figure S1 b). We constructed upset plots using grid and
watershed units with the UpSetR package in R version 4.02.
1.5.2 Genetic divergence and bigeographical distribution analysis of