Spatial and environmental factors shape multiple facets of macrophyte β-diversity in tropical freshwaters, revealing dispersal and adaptive patterns.

Dispersal processes, reproductive traits and adaptive dynamics shape aquatic plant (macrophyte) metacommunities. In this study, we explore how environmental and spatial factors influence differences in plant communities across sites, a concept known as beta (β)-diversity, which we assess from the following three perspectives: species identity (taxonomic), functional traits (functional) and evolutionary history (phylogenetic). We surveyed tropical lentic (39) and lotic (85) ecosystems, totalling 124 waterbodies. We analysed β-diversity components (replacement and richness difference) using dispersal traits (vegetative propagation, seed dispersal and life history) and the species' phylogeny. In lentic ecosystems, replacement and richness differences contributed equally to functional and phylogenetic β-diversity. Richness differences dominated functional β-diversity in lotic ecosystems, while phylogenetic β-diversity remained balanced. Taxonomic β-diversity was largely driven by replacement in both ecosystems. Spatial factors structured macrophyte metacommunities in lentic ecosystems, while spatial and environmental factors influenced lotic ecosystems. These findings reveal how connectivity, isolation and dispersal limitations shape macrophyte communities in contrasting environments. Incorporating phylogenetic β-diversity deepened the understanding of evolutionary relationships in community assembly. This study emphasizes the importance of incorporating the multidimensionality of diversity to uncover key mechanisms driving tropical aquatic ecosystems and inform conservation strategies addressing environmental degradation and the ecological services aquatic plants provide.