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Aquatic macrophytes encompass a highly diverse group of plants with different strategies, niche requirements, and dispersion capacities. Therefore, macrophyte life forms can respond distinctly to environmental factors. We analyzed whether emergent/amphibious, floating-leaves/rooted submerged, and free-floating/free-submerged macrophytes respond differently to local, spatial, and land use variables in ponds and streams of the Amazon. We sampled macrophytes and physical and chemical variables in 158 sites in the Pará state, Brazil. Land use and land cover were obtained via satellite images. A total of 264 macrophyte taxa were recorded, including 234 amphibious/emergent, 17 floating-leaves/rooted submerged, and 13 free-floating/free-submerged. The highest total beta diversity was recorded for amphibious/emergent species (0.47), followed by free-floating and floating submerged (0.41), and floating-leaves and rooted submerged species (0.39). The replacement component explained the greatest proportion of total beta for the three macrophyte groups, with values higher than 60 %. The spatial component greatly influenced the total beta diversity of amphibious/emergent (R 2  = 0.06) and floating-leaves/rooted submerged life forms (R 2  = 0.08). Meanwhile, local variables were more associated with the total beta diversity of free-floating/free-submerged macrophytes (R 2  = 0.06). Free-floating and free-submerged life forms were the only groups influenced by land use changes (R 2  = 0.02), and their richness difference between sites was spatially structured (R 2  = 0.10). Our study is one of the first to explore the combined effects of local, spatial, and land use variables on macrophyte life forms. These results are important for deeply understanding macrophyte structure in Amazon environments, threatened by anthropic activities and planning conservation strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Integrating the physicochemical characteristics of aquatic environments with their biotas is essential for the conservation and monitoring of biodiversity, given the sensitivity of both the biotic and the abiotic components to environmental changes linked to water quality and human activities. In the present study, we evaluate how the contributions of different taxa to beta diversity, through local and species effects, can indicate the priority sites for conservation and ecological restoration in an Amazon region impacted by bauxite mining. We also investigate how environmental conditions at local and landscape scales influence the beta diversity of the aquatic biota. We hypothesize that unique species assemblages (a high local contribution) are more likely to be found in more degraded streams, with these assemblages being influenced strongly by local conditions and landscape characteristics. Our findings indicate that local contributions to beta diversity can be explained significantly by physicochemical variables, such as the pH and electrical conductivity of the water, with streams impacted by mining exhibiting distinct species compositions. The environmental factors affected different biological groups in distinct manners, including fish, aquatic insects (water bugs, and the larvae of mayflies, stoneflies, caddisflies, and dragonflies), adult dragonflies, and macrophytes. Streams with unique communities also often exhibited low species richness, which highlights the need for environmental restoration. These results reinforce the value of the use of beta diversity metrics as guidelines for conservation and restoration efforts in aquatic ecosystems that have been affected by anthropogenic disturbances. Furthermore, our findings underscore the importance of a multi-taxon approach to ensure the formulation of a more comprehensive picture of the responses of a region's biodiversity to anthropogenic impacts., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Leandro Juen reports financial support and administrative support were provided by Norsk Hydro Paragominas - Barcarena. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The role of the native species richness and density in ecosystem invasibility is a matter of concern for both ecologists and managers. We tested the hypothesis that the invasiveness of Urochloa arrecta (non-native in the Neotropics) is negatively affected by the species richness and abundance of native aquatic macrophytes in freshwater ecosystems. We first created four levels of macrophyte richness in a greenhouse (richness experiment), and we then manipulated the densities of the same native species in a second experiment (density experiment). When the native macrophytes were adults, fragments of U. arrecta were added, and their growth was assessed. Our results from the richness experiment corroborated the hypothesis of a negative relationship between the native species richness and the growth of U. arrecta, as measured by sprout length and root biomass. However, the resistance to invasion was not attributed to the presence of a particular native species with a greater competitive ability. In the density experiment, U. arrecta growth decreased significantly with an increased density of all five of the native species. Density strongly affected the performance of the Poaceae in a negative manner, suggesting that patches that are densely colonized by native macrophytes and less subject to disturbances will be more resistant to invasion than those that are poorly colonized and more commonly subjected to disturbances. Our density experiment also showed that some species exhibit a higher competitive ability than others (sampling effect). Although native richness and abundance clearly limit the colonization and establishment of U. arrecta, these factors cannot completely prevent the invasion of aquatic ecosystems by this Poaceae species.

In the last three decades, rapid assessment surveys have become an important approach for measuring aquatic ecosystem biodiversity. These methods can be used to detect anthropogenic impacts and recognize local or global species extinctions. We present a floristic survey of the aquatic macrophytes along the Brazilian margin of the Itaipu Reservoir conducted in 2008 and compare this with a floristic survey conducted ten years earlier. We used ordination analysis to determine whether assemblage composition differed among reservoir arms. Macrophyte species were sampled in each of the 235 sampling stations using a boat, which was positioned inside three places of each macrophyte stand to record species and search for small plants. We also collected submerged plants using a rake with the boat moving at constant velocity for ten minutes. We assigned individual macrophyte species to life form and identified representative species for each life form. A total of 87 macrophyte taxa were identified. The "emergent" life forms contained the highest number of species, followed by "rooted submerged" life forms. The extensive survey of macrophytes undertaken in September 2008 recorded more species than a survey conducted between 1995 and 1998. This could be due to changes in water physico-chemistry, disturbances due to water drawdown and the long period between surveys, which may have allowed natural colonization by other species. Additionally, differences in the classification systems and taxonomic resolution used in the surveys may account for differences in the number of species recorded. Assemblage composition varied among the arms and was affected by underwater radiation (as measured using a Secchi disk) and fetch. Five non-native species were found. Two of these non-native species (Urochloa subquadripara and Hydrilla verticillata) are of special concern because they have a high frequency of occurrence and occupy large marginal areas of the reservoir. Future surveys should be conducted to determine the habitat most frequently colonized by these species. This would allow management strategies to be developed to protect native aquatic biota and prevent interference with the recreational and commercial uses of the Itaipu Reservoir.

Chalcopteryx rutilans Rambur, 1842 (Polythoridae, Odonata) is a species widely distributed in central Amazonia. Due to its sensitivity to environmental changes, it is a bioindicator species used to evaluate the environmental conditions of streams in federally protected areas. By sequencing C. rutilans mitogenome, we report the first whole mitogenome from the Polythoridae family and the first from an Odonata species endemic to South America. The entire mitogenome has 15,653 bp and contains 13 protein-coding, 22 tRNA, and two rRNA genes. The nucleotide composition of the mitogenome is 42.7%, T: 25.5%, C: 19.4%, and G: 12.4%. The AT and GC skews of the mitogenome sequence were 0.249 and −0.220, respectively. C. rutilans was recovered as a sister to Pseudolestes mirabilis Kirby, 1900 (Pseudolestidae), demonstrating the absence of mitogenomes of species from multiple families in the current literature. Mitogenome data from this study will provide useful information for further studies on the phylogeny and conservation of Polythoridae. [ABSTRACT FROM AUTHOR]