Regional macrophyte diversity is shaped by accumulative effects across waterbody types in southern China

Studies on aquatic biodiversity in different waterbody types have attracted significant attention worldwide to achieve the goal of freshwater conservation. Different freshwater habitats can help maintain regional biodiversity by directly supporting aquatic plants and forming networks to promote aquatic dispersal across regions. However, few studies have conducted large-scale comparisons of macrophyte diversity among different waterbody types in China due to a lack of a national macrophyte dataset. Here, we compared species richness, species composition, beta diversity, and its components among ponds, ditches, disturbed ponds, lakes, rivers, and reservoirs in southern China. We found that macrophyte species composition overlapped in the different waterbody types, indicating similar regional species pools. Species composition was best explained by temperature, elevation, and flow velocity. For species richness, ponds supported the highest number of species, followed by lakes, ditches, rivers, and reservoirs, with disturbed ponds showing the lowest diversity. For beta diversity, the relatively low turnover and high nestedness in the lakes indicated high dispersal of macrophyte species throughout these water bodies or suggested that human disturbance in lakes may lead to a more uniform chemical environment and thus regional macrophyte community. This study emphasized the importance of maintaining the diversity of different waterbody types in the landscape and determining the most threatened freshwater habitats. Moreover, small water bodies (e.g., ponds) contribute more to the regional macrophyte species pool than permanent water bodies (e.g., lakes) due to their relatively high biodiversity value. Their stable hydrological environment may help maintain rare and uncommon species that do not appear in other waterbody types. •Composition was best explained by temperature, elevation and flow velocity.•Pond support the highest species richness, followed by lake, ditch, river and reservoir, with disturbed pond the least.•ponds tend to have high turnover and low nestedness while lakes hold opposite trend.•Turnover responses strongly to depth in deep rivers, which should be protected.