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We carried out a literature review to investigate the taxonomic and functional β diversity of zooplankton and its species replacement (βrepl) and richness difference (βrich) components in Brazilian rivers. In addition, the taxonomic (LCBD-t) and functional ecological uniqueness (LCBD-f) were also measured. We tested the following hypotheses: (i) The βrepl component is the main driver of taxonomic β diversity, while βrich is most important for functional β diversity, due to functional simplification; (ii) Sites with lower taxonomic and functional richness are the ones that most contribute to LCBD. Contrary to expectations, βrich drove the taxonomic and functional β diversity. This may have occurred due to environmental constraints and geographic distance, thus causing a loss or gain of species and traits between hydrographic regions. For just two regions, the sites with the lowest functional richness were the ones that most contributed to LCBD-f. This reinforces that sites with lower richness can support species that perform unique functions in the ecosystem. As studies involving zooplankton from lotic systems are still limited in Brazil, we suggest that future research should consider the patterns of β diversity in these dynamic, diverse, and threatened aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Environmental and dispersal drivers are determinants of periphyton metacommunities. However, the effects of these predictors can vary according to the facet of biodiversity assessed. In this study, we assessed the relative importance of local environment (i.e., limnological variables), regional landscape (i.e., land use), and spatial distance (i.e., overland and watercourse dispersal routes) components for the periphytic community in 30 Cerrado stream sites. For this, we estimated different metrics, such as the total density, beta diversity, local contribution to beta diversity (LCBD), species richness, and composition. This last metric was obtained considering the complete and deconstructed communities according to the type of adhesion to the substrate. We found 128 species with a predominance of the Bacillariophyceae, of which most have loosely adherence to the substrate. The algae community showed a high turnover of species along the hydrographic drainage. Besides, spatial distances were significant for species richness, total density, and species composition metrics using overland or watercourse distances. The spatial distance was also crucial for species composition tightly adhered to the substrate. Nevertheless, any community metric had no local environment and regional landscape effects. Therefore, on a large spatial scale, the effect of the spatial component can be attributed to species dispersion limitation, whereas on a finer spatial scale, mass effect was the primary process driving the variation among communities. In this sense, while for some species dispersal is limited by higher distances, for others dispersing to streams with suboptimal conditions can be associated with physiological aptitudes and high reproductive rates, which allow for the maintenance of species in the studied stream sites. [ABSTRACT FROM AUTHOR]

The way species respond to environmental changes depends on several factors, but mainly on their niche breadth in the face of habitat variability and changes. Our study evaluated, over a six-year period, how the abundance and richness of generalist and specialist genera of Ephemeroptera, Plecoptera and Trichoptera (EPT) respond to mining activities in the Carajás National Forest, Pará state, Brazil. We hypothesized that the abundance and richness of specialist genera would be lower in streams impacted by mining. We collected 49,822 individuals, distributed in 31 genera classified as specialists and 28 as generalists. Using Generalized Linear Mixed Models (GLMM) we found that there was a negative effect of mining on the estimated richness of specialists and, contrary to what we expected, there was a positive effect of mining on the abundance of specialists. On the other hand, the generalists negatively responded to the mining in the estimated richness and abundance. Specialists in streams affected by mining may increase their abundances due to habitat homogenization. Therefore, partitioning the assemblage into generalist and specialist groups has important applications in monitoring and better understanding assemblage patterns and how they are affected by anthropogenic effects, specifically mining. [ABSTRACT FROM AUTHOR]

Metacommunity structure depends on environmental and spatial factors. Stream fishes are constrained to disperse within dendritic networks and waterfalls and other barriers add resistance to species dispersal. We evaluated the importance of environmental and spatial effects on fish metacommunity composition, adopting different models of spatial distance: overland, watercourse, resistance (physical barriers), cost distance (watercourse resistance), and asymmetrical dispersal (considering flow direction). Fishes were sampled in 31 riffle sites of a small subtropical basin of southern Brazil (~ 250 km2 effective study area). Using redundancy analysis (RDA) and variance partitioning, we found the best model was the one including flow direction weighted by watercourse distance plus environmental variables (overall adj-R2 = 0.42). However, the explanation of fish composition was greatly improved by weighting spatial distance by stream channel sinuosity or height of barriers. Reach slope and width were the two significant environmental variables. Our study supports that dispersal, in addition to environmental factors, affects stream fish metacommunity even in a watershed of small spatial extent. Detecting spatial effects in a small watershed depends on considering realistic watershed features that affect fish dispersal in drainage networks such as waterfalls and other physical barriers, and distance along the watercourse and flow direction. [ABSTRACT FROM AUTHOR]

Some local communities contribute more to beta diversity than others, which has been known as compositional uniqueness or local contribution to beta diversity. Compositional uniqueness should correlate positively with environmental uniqueness and site isolation. We evaluated compositional uniqueness (total and in terms of species replacement and nestedness) of periphytic diatoms and insects in subtropical streams and tested for correlates of these metrics. We sampled 90 riffles in a near-pristine catchment in the southeast Atlantic Forest of Brazil. The total compositional uniqueness for diatoms and insects were not associated to riffle position. However, the total compositional uniqueness of diatoms (presence–absence data), was correlated with the uniqueness of streambed substrate composition, while the total compositional uniqueness of insects did not correlate with any explanatory variable. The compositional uniqueness in terms of nestedness (presence–absence data) for diatoms and for insects (abundance data) was correlated positively with the uniqueness of substrate composition. Compositional uniqueness in terms of species replacement (abundance data) for insects was correlated negatively with the uniqueness of substrate composition. Our results indicate that subtle differences in environmental uniqueness, play a role in determining beta diversity in near-pristine streams. However, finding strong correlates of compositional uniqueness proved to be a difficult task. [ABSTRACT FROM AUTHOR]

Hydrological regimes are seasonally variable in river-floodplain ecosystems. Thus, since in these environments the local and regional factors change at different temporal scales, factors structuring metacommunities might also differ over time. However, temporal dynamics of metacommunities have rarely been assessed. Here, we investigated the influence of environmental and spatial factors over time on the metacommunity structuring of periphytic ostracods in the river-floodplain system of the Upper Paraná River (Brazil). The spatial factors turned out to be more important than environmental factors, and differences in the percentage of explanation of the factors structuring ostracod metacommunities over time were significant, mainly during extreme drought period. Our results showed that the high spatial influence might be related to the low connectivity amongst environments during such extreme drought period, which can increase dispersal limitation, and consequently can increase the turnover of ostracod species throughout the region, leading to a higher beta-diversity of ostracod metacommunities. [ABSTRACT FROM AUTHOR]