Species diversity is determined by both local environmental conditions that control differentiation and extinction and the outcome of large-scale processes that affect migration. The latter primarily comprises climatic change and dynamic landscape alteration. In the past few million years, both Southeast Asia and Eastern Africa experienced drastic climatic and geological oscillations: in Southeast Asia, especially in China, the Tibetan Plateau significantly rose up, and the flow of the Yangtze River was reversed. In East Africa, lakes and rivers experienced frequent range expansions and regressions due to the African mega-droughts. To test how such climatic and geological histories of both regions relate to their respective regional species and genetic diversity, a large scale comparative phylogeographic study is essential. Bellamya, a species rich freshwater snail genus that is widely distributed across China and East Africa, represents a suitable model system to address this question. We sequenced mitochondrial and nuclear DNA for members of the genus from China and used published sequences from Africa and some other locations in Asia to investigate their phylogeny and distribution of genetic diversity. Our phylogenetic analysis revealed two monophyletic groups, one in China and one in East Africa. Within the Chinese group, Bellamya species show little genetic differentiation. In contrast, we observe fairly deep divergence among the East African lakes with almost every lake possessing its unique clade. Our results show that strong divergence does not necessarily depend on intrinsic characteristics of a species, but rather is related to the landscape dynamics of a region. Our phylogenetic results suggest that the Bellamya in China and East Africa are independent phylogenetic clades with different evolutionary trajectories. The different climate and geological histories likely contributed to the diverging evolutionary patterns. Repeated range expansions and regressions of lakes likely contributed to the great divergence of Bellamya in East Africa, while reversal of the river courses and intermingling of different lineages had an opposite effect on Bellamya diversification in China.

Three common floating bed plants, Eichhornia crassipes, Pistia stratiotes, and Ipomoea aquatica, were selected in the present study to investigate their inhibitory effects on toxic Microcystis aeruginosa. The results showed that all three types of floating-bed plants could considerably inhibit the growth of M. aeruginosa and effectively remove the microcystins (MCs) from water systems, among which, E. crassipes and P. stratiotes were more effective in resisting M. aeruginosa, and the removal rate of the intracellular MCs could be up to 100%. In addition, the roots and leaves of the three plants were enriched with a large number of MCs and demonstrated significant antioxidant responses, as evidenced by the increase in the content of catalase (CAT), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), and malondialdehyde (MDA) in the roots, stems, and leaves of the plants. Furthermore, this study also showed that Proteobacteria, Bacteroidota, Myxococcota, Verrucomicrobiota, and Actinobacteriota dominated the root microorganisms of the three plants. Moreover, a variety of MC-degrading bacteria, including Sphingomonas, Acinetobacter, Novosphingobium, and Pseudomonas, were found at the genus level, which further provides important basic data for the regulation of eutrophic water bodies and the removal of MCs.