Occurrence and environmental data
We obtained locality point data for Scutiger boulengeri from our
own fieldwork and the published literatures (Li et al. 2009, Hofmann et
al. 2017). Localities cover Himalayas, QTP, Hengduan Mountains,
Min
Mountains and adjacent Mountains (Figure 1). Our final dataset comprises
96 geo-referenced occurrence records: 42 for East represented by 4
clades (9 for E. A clade, 9 for E. B, 10 for E. C, 14 for E. D) and 54
for West represented by 2 clades (35 for W. a clade and 19 for W. b).
We compiled 19 environmental variables and elevation for each period
from the WorldClim database (Hijmans et al. 2005a) with a resolution of
30 seconds (~ 1 km) for each environment layer (Hijmans
et al. 2005b). We included the dissimilarity of the enhanced vegetation
index variable, drawn from the Global Habitat Heterogeneity project
(Tuanmu and Jetz 2015). Because strong colinearity between environmental
variables could inflate model accuracy (Veloz 2009, Boria et al. 2014),
we examined pairwise correlations among the 21 variables within each
clade distribution. We reduced autocorrelation of input environmental
data by removing highly correlated variables with the threshold of
Pearson’s correlation tests |r| >0.8
(Dormann et al. 2013). Finally, we chose 8 variables with lower
correlation for subsequent analyses.