FIGURE 2 The relative predictive power of different environmental
variables based on the jackknife test and permutation importance in
MaxEnt for Francois’ langur
3.3 Response of environmental variables
Species response curves revealed the relationship between environmental
variables and the probability of species presence, indicating biological
tolerances for target species and habitat preferences. Based on the
acquired species response curves (Appendix 2), Francois’ langur prefers
habitats with mean diurnal range (mean of monthly (max temp-min temp))
(bio2) less than 6◦C, min temperature of coldest month (bio6) of 9-11◦C,
temperature annual range (bio7) of 21-23◦C, precipitation seasonality
(coefficient of variation) (bio15) less than 65mm, precipitation of
coldest quarter (bio19) from 70 to 80mm. Meanwhile, the probability of
Francois’ langur presence increases with increasing the distance to road
in the range of 0-15km, distance to housing in the range of 0-30km and
NDVI from 0 to 0.8. The probability of Francois’ langur presence
decreases as the distance to river increases.
3.4 Current potential distribution
A map of current habitat suitability for Francois’ langur based on
MaxEnt model predictions is shown in Figure 3; it is based on the 12
environmental variables and the current occurrence data of Francois’
langur. All 82 occurrences of Francois’ langur fell within the predicted
suitable area, again indicating that the model performed well and
produced excellent evaluation. The total suitable habitat area was
predicted to be 144207.44 km2 (29.09% of the study
area), of which the highly suitable area (0.45-1) covered 13108.55
km2 (9.09% of the total suitable area); the
moderately suitable area (0.25-0.45) covered 21157.41
km2 (14.67% of the total suitable area) and the
poorly suitable area (0.04-0.25) covered 109941.49 km2(76.24% of the total suitable area). The highly suitable areas were
located in a small part of southwest Guangxi, east of Chongqing and on
the border between Guizhou and Chongqing. The moderately suitable
habitats were close to the highly suitable ones with different
expansion. Less suitable areas, which were fragmented, were mainly
located in Guizhou, some parts of Chongqing except the northern area and
southwest of Guangxi (Figure 3).