Objective This paper aims to study the current and the potential suitable areas of the invasive alien weeds Tithonia diversifolia A. Gray and Synedrella nodiflora (L.) Gaertn. in China, and to explore the main environmental variables affecting the distribution of these two plants. It provides a theoretical reference for the invasion monitoring of these two invasive weeds and for mastering their diffusion and distribution patterns.

Method Fit analysis on the species distribution data and correlation analysis on the environmental variables were employed, and ENMeval was used to optimize the model of the species distribution data. The obtained distribution data, environmental variables, regularization multiplier (RM) and feature combination (FC) parameters were imported into MaxEnt for distribution prediction. Then, ArcGIS was used to obtain the current and potential suitable distribution areas.

Result The standard deviation of seasonal temperature change and the average temperature in the coldest quarter were the main environmental variables affecting the distribution of T. diversifolia, and the sum of their contribution rates reached 70.8%. The range of annual average temperature change, annual average precipitation and precipitation in the wettest month were the main environmental variables affecting the distribution of S. nodiflora, with the sum of their contribution rates reaching 76.7%. The moderate and high suitable areas of these two plants were distributed in southern Tibet, Yunnan, Guangxi, Guangdong, Fujian, Hainan and Taiwan of China.

Conclusion Both T. diversifolia and S. nodiflora. have successfully invaded China, and are currently mainly distributed in some tropical and subtropical areas in southern China. It is predicted that they have a trend of gradually expanding towards the inland. Therefore, stronger precautions should be taken against their invasion.