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Isoetes L. is a relict genus of Isoetaceae which is of great value to study the systematic evolution of ferns and the flora of East Asia. Due to the impact of human activities on aquatic habitats, the population of Isoetes L. in China is decreasing. In this paper, based on environmental variables including bioclimate, soil factors, elevation, UV-B radiation and human footprint index, the potential distribution of Isoetes L. was simulated using MaxEnt and GARP. Results showed that the AUC and Kappa values of MaxEnt and GARP under human activities were higher than that without human activities. The suitable habitat of Isoetes L. simulated by GARP was much wider than by MaxEnt. By comparison, MaxEnt had more accurate prediction results. Furthermore, the MaxEnt model results showed that, the highly suitable habitats were mainly distributed in western Sichuan, central and northern Yunnan, eastern Tibet, central and eastern Hunan, most of Zhejiang, western Guizhou, southern Anhui and eastern Hebei, with a total area of 55.45 × 104 km2. Under the influence of human activities, the area of highly, moderately and poorly suitable habitats decreased by 61.14%, 44.28% and 56.72%, respectively. Protection gap areas of Isoetes L. were mainly located in western Sichuan, northern Yunnan, western Guizhou, eastern Tibet, central and eastern Hunan and most of Zhejiang. Precipitation of warmest quarter, human footprint index, min temperature of coldest month, precipitation seasonality, elevation and mean UV-B of highest month were the main variables influencing the distribution of Isoetes L. Our results provide a favorable basis for the effective conservation of wild resources of Isoetes L. in China.
Yang et al. (Mon,) studied this question.