Abstract:

Objective: Based on the spatial distribution data of genus Sapindus in China, the suitable range for distribution and main ecological characteristics of Sapindus were explored to provide the scientific basis for seed allocation, protection of genetic diversity of germplasm resources, introduction and cultivation, site selection of Sapindus. Method: Based on the spatial distribution data of 133 representative accessions of germplasm resources of Sapindus which screened from 226 accessions of germplasm resources by overlay analysis, combined with 24 ecological factors, the maximum entropy model (MaxEnt) was used to establish the relationship model with the ecological factors for the prediction of the potential distribution area of Sapindus. The model uses the receiver operating characteristic curve (ROC curve) to check the accuracy and uses the Jackknife method to screen the dominant ecological factors. The model is combined with the ArcGIS system to realize the visualization of Sapindus potential distribution area in China. Result: Simulation of the MaxEnt model displayed a high credibility, and the AUC values of the training set and test set of the ROC curve of the Sapindus distribution were both above 0.990. The area of the potential distribution of Sapindus is 248.71×10⁴ km², accounting for 25.81% of the total land area of China. S. mukorossi is 240.66×10⁴ km² (24.99%), S. delavayi is 78.99×10⁴ km² (8.20%), and Sapindus rarak is 100.40×10⁴ km² (10.42%). The ecological factors that significantly affected the suitable distribution of S. mukorossi are the precipitation of the warmest quarter (57.1%) and Isothermality (22.6%). The significant ecological factors of S. delavayi are the precipitation of warmest quarter (37.9%), mean temperature of coldest quarter (15.9%), elevation (12.8%), and precipitation seasonality (11.2%). The significant ecological factors of S. rarak are temperature annual range (19.6%), precipitation of warmest quarter (17.8%), oxygen availability to roots (11.9%), and isothermality (11.1%). Conclusion: The potential occurrence area of Sapindus are widely distributed in central and southern China; The highly favorable area of S.mukorossi is mainly distributed in Fujian Povince, Guangxi Zhuang Autonomous Region, Guizhou Province, Chongqing City, northern Guangdong Province, Nanchang, and Ganzhou Cty in Jiangxi Province and Sichuan Basin in Sichuan Province. The highly favorable area of S. delavayi is concentrated in Sichuan Basin in Sichuan Province, Kunming, and Qujing Cty in Yunnan Povince. The highly favorable area of S. rarak is concentrated in Yuxi, Pu'er, Honghe Hani Yi Autonomous Prefecture, Wenshan Zhuang Autonomous Prefecture, and other regions in southern Yunnan Province. The precipitation of the warmest quarter is the most significant ecological factor that determines the potential distribution area of the genus Sapindus and the three species of the genus. S. mukorossi is suitable for the region of precipitation of warmest quarter range from 400 mm to 800 mm, isothermality range from 24% to 35%. Compared to S. mukorossi, S. delavayi is suitable for the region of high elevation (1 200~3 000 m) and moderate mean temperature of coldest quarter (4~11℃). And S. rarak is suitable for the tropical regions where the temperature annual range from 14℃ to 24℃ and the precipitation of warmest quarter range from 550 mm to 1 550 mm.

Key words: MaxEnt, Sapindus, suitable habitat, ecological characteristics