Land use increases macrophytes beta diversity in Amazon streams by favoring amphibious life forms species

Land use has transformed landscapes, altered water and soil physical–chemical parameters, reduced habitat availability, and limited species occurrence. Here, we investigated the contribution of sites (local contribution to beta diversity—LCBD) and species (species contribution to beta diversity—SCBD) to macrophyte total β -diversity in streams inserted in a gradient of land use. We also investigated which life forms are important to SCBD and which environmental parameters are related to the change in the species composition. Sampling took place in 17 streams located in Paragominas, Pará, Brazil in September 2017. We recorded 36 species and four life forms. We identified five sites with high LCBD. The species with the four highest SCBD scores belong to the amphibious life form. CDI (Catchment Disturbance Index) and canopy cover, variables that show land use degrees, drove the distribution of macrophyte species in the land use gradient. CDI presented a positive relationship with LCBD, whereas canopy cover presented a negative relationship, i.e., a greater composition of unique species and greater diversity of macrophytes life forms were found in more altered streams than in preserved ones, due to canopy openness. Nonetheless, we emphasize that although the environmental characteristics of altered streams favored the establishment of more macrophytes species, the species found could be generalists and the pattern for other types of environments is usually the opposite. Therefore, studies focusing on temporal patterns will be important for this area to understand how the macrophyte community will stabilize. This study brings important contributions to elucidate the effects of land use on macrophytes distribution and the role played by different life forms.