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Understanding community assembly in habitat patches requires an integrative approach, considering the potential role of local and regional factors and organisms' dispersal abilities among patches. For this, assessing the degree of species overlap between patches (nestedness) can be particularly informative, especially regarding different taxa and distinct patch properties.We assessed the potential role of landscape‐patch structure in shaping the nestedness patterns of five taxonomic groups with distinct dispersal abilities (ants, bees, dung beetles, fruit‐feeding butterflies and aculeate wasps).We collected insects from 11 forest patches in the Espinhaço mountain range in southeast Brazil. We assessed the potential contribution of three forest island attributes (size, distance and shape) to the nestedness of insect communities and then tested if metacommunities were significantly nested with respect to habitat (forest islands). Finally, we evaluated how species of each taxonomic group contribute to metacommunity nestedness.While there was a substantial variation in the contribution to the nested pattern within each taxon, all taxa studied exhibited a significantly nested pattern of species distribution. The landscape‐patch structure and the vagility of the different taxa did not influence the contribution of sites to the metacommunity nested pattern.Our integrative approach provides critical data on the role of different factors in shaping species distribution in natural patches. Species with different dispersal abilities and patches with distinct landscape properties contributed similarly to nestedness, indicating the potential role of the vegetation matrix permeability in shaping the distribution of organisms in the studied forest archipelago. [ABSTRACT FROM AUTHOR]

Ecological drift can override the effects of deterministic niche selection on small populations and drive the assembly of some ecological communities. We tested this hypothesis with a unique data set sampled identically in 200 streams in two regions (tropical Brazil and boreal Finland) that differ in macroinvertebrate community size by fivefold. Null models allowed us to estimate the magnitude to which β‐diversity deviates from the expectation under a random assembly process while taking differences in richness and relative abundance into account, i.e., β‐deviation. We found that both abundance‐ and incidence‐based β‐diversity was negatively related to community size only in Brazil. Also, β‐diversity of small tropical communities was closer to stochastic expectations compared with β‐diversity of large communities. We suggest that ecological drift may drive variation in some small communities by changing the expected outcome of niche selection, increasing the chances of species with low abundance and narrow distribution to occur in some communities. Habitat destruction, overexploitation, pollution, and reductions in connectivity have been reducing the size of biological communities. These environmental pressures might make smaller communities more vulnerable to novel conditions and render community dynamics more unpredictable. Incorporation of community size into ecological models should provide conceptual and applied insights into a better understanding of the processes driving biodiversity. [ABSTRACT FROM AUTHOR]

The aquatic microbiota plays key roles in ecosystem processes; however, the mechanisms that influence their biogeographic patterns are not yet fully understood. Using high-throughput 18S rDNA gene sequencing, we investigated the composition of planktonic microeukaryotes (organisms sampled using a 68-μm plankton net) in 27 floodplain lakes of the Araguaia River, central Brazil and explored the influence of environmental and spatial factors for communities considering taxonomic and trophic groups. Of the 807 operational taxonomic units (OTUs) observed, Chlorophyta and Charophyta were the groups with greater abundance. Beta diversity was high, and the similarity of communities decreased as the geographic distance increased. We found a shared explanation between environmental and spatial predictors for total and autotrophic microbiota. Environmental variables influence only mixotrophic microbiota. These results suggest an OTU turnover along the floodplain and a spatially structured composition. This spatial pattern can be derived from the association with extrinsic factors, such as spatially structured environmental variables, that generate spatial dependence. However, the relationship between the composition of microbiota and environmental conditions is still unclear. [ABSTRACT FROM AUTHOR]

Aim: Our aim was to uncover patterns of distribution of marine subtidal rocky reef communities across six taxonomic groups and decompose the relative roles of species loss and turnover in total community variation. Additionally, we propose an easily calculated index that can be used to highlight areas with unique species composition for conservation planning. We estimated the strengths of associations between environmental factors and species richness and rarity. Location: Ilha Grande Bay, Brazil, covering about 150,000 ha harbouring different marine habitats. Methods: We used the Marine Rapid Assessment Protocol at 42 sites to gather information on environmental variables and species in six subtidal marine groups. We determined "singular" sites as the regions harbouring higher numbers of rare species. Then, we estimated the roles of species loss and turnover on the observed total variation among sites. We used Generalized Linear Model to partition the relative importance of the selected environmental factors in driving variation in species richness and singularity. Results: The singularity index and richness showed that the bay could be divided into three subregions for subtidal communities. Richness and rarity were structured at different spatial scales and associated with environmental variables related to water productivity and nutrients but varied among taxonomic groups. Community variation over space was largely associated with turnover of species. Main conclusions: Higher singularity and richness on the western side of the bay and around the main island suggested that these regions should be conservation priorities, but high species turnover across the whole bay indicated that portions of the central channel should be included in conservation strategies. This draws attention to the importance of community variation rather than just species numbers in conservation and management planning. The high species turnover indicated that these rocky reefs have high beta diversity when compared to other studied biological systems. [ABSTRACT FROM AUTHOR]

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