ObjectiveClematis pinnata, a sub-shrub or vine, is restricted to small areas of northern China, including Beijing, Hebei Province, Tianjin of northern China, and Liaoning Province of northeastern China. Due to its ambiguous morphological characters, this species often does not attract attention and there have been very few studies on this species.

MethodIn this study, we predicted the potential distribution area and suitable distribution habitat of this species using MaxEnt model and ArcGIS technique. We carefully verified 22 specimen localities of C. pinnata and recognized that Harbin is not a distribution site of this species.

ResultMaxEnt analysis showed that the most suitable area of C. pinnata was concentrated in Hebei, Beijing, Tianjin, and adjacent area of Liaoning Province. Shanxi Province had a vast suitable area for C. pinnata, although there were no records of this species in Shanxi Province. The AUC of the ROC curve was 0.995, showing a high precision of the prediction analysis. The key environmental factors determining the potential distribution were precipitation seasonality (the contribution rate, 39.6%), temperature annual range (14.5%), altitude (14.4%), precipitation of the warmest quarter (11.3%), precipitation of driest quarter (9.5%). Those environmental variables in the most suitable areas were calculated as precipitation seasonality 126.78, temperature annual range 42.41℃, altitude 372.04 m, precipitation of the warmest quarter 436.67 mm, precipitation of the driest quarter 11.59 mm.

ConclusionClematis pinnata is a narrowly distributed species, mainly influenced by the above mentioned ecological factors. According to IUCN standard, it belongs to the grade VU (vulnerable). The species should be protected using ex-situ conservation method. Furthermore, we propose that distribution records of the organisms using for MaxEnt analysis should be strictly identified to verify the accuracy of the results.