Compositional and phylogenetic beta diversity reveal different patterns of aquatic plant assemblages in lakes along the Changjiang River

Many articles have examined the aquatic flora in lakes along the Changjiang River over the past four decades. However, studies on taxonomic and phylogenetic alpha and beta diversity of aquatic plants along the Changjiang River are lacking. In order to clarify the distribution pattern of aquatic plants in lakes of the Changjiang River, we comprehensively analyzed the phylogenetic structure, compositional beta diversity (CBD), and phylogenetic beta diversity (PBD) of their aquatic plant assemblages. We found strong regional differences in phylogenetic community structures with significant differences in the net relatedness index and nearest taxon index values at subregional scales. Interestingly, similarity clustering based on compositional beta similarity showed that the lakes in the upper Changjiang River and upper Pearl River were clustered into a branch, and then connected with the lakes in the lower Changjiang River. However, similarity clustering based on phylogenetic beta similarity clustered the lakes in the upper and lower Changjiang River together into a branch, before connecting them with the lakes in the upper Pearl River. Additionally, we found significantly higher taxonomic dissimilarity than phylogenetic dissimilarity overall, as well as in individual subregions of the Changjiang River. These results suggested that the uplift of the Qinghai-Tibet Plateau and river capture played important roles in the aquatic plant assemblages of lakes resulting in patterns of geographic endemism at regional scales.