Diversity and environmental determinants of aquatic plants across China

Aquatic plants play an important role in aquatic systems. A comprehensive understanding of their spatial distribution may help to develop biodiversity conservation plans. This work investigated the spatial distribution of aquatic plants across China, including the invasive, threatened, and province-endemic species. Correlation analysis was used to evaluate the effects of environmental variables on richness pattern and variation partitioning was used to reveal the pure and shared effects of four explanatory variable groups: energy-water availability, geographical location, habitat heterogeneity, and human impact on species richness. Results showed that aquatic plants were unevenly distributed in China and they decreased from southern China toward northern China. Yunnan Province was the hotspot of aquatic plants. The number of invasive species was more in southeast China and less in northwest China. The endemism of aquatic plants in each province was not obvious. Aquatic plant richness across China tended to be higher in areas where the energy and water supply are adequate and actual evapotranspiration was the strongest correlate for total species richness (r = 0.630). Among the three growth forms, the correlation between submerged species richness and environmental factors was weak, while that of floating plants was strong. According to variation partitioning, the shared effect of energy-water availability and geographical location was dominant in aquatic plant richness pattern across China (R2 = 0.47 for total species richness). Pure spatial factors had a weak effect in shaping the richness pattern, suggesting that dispersal limitations have no significant effect on the distribution pattern of aquatic plants for their relatively strong dispersal capacity. Moreover, the effects of habitat heterogeneity and human impact on total aquatic plant richness pattern were also weak.