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).