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Aims We aimed at disentangling the effects of spatial distance, current, and past environmental dissimilarity, and their combinations on tree community taxonomic and phylogenetic turnover by addressing the following questions: a) Is tree community taxonomic and phylogenetic turnover related to the indirect effects of spatial distance via environmental dissimilarity? b) Does tree community taxonomic and phylogenetic turnover respond to paleoclimate (Last Glacial Maximum and Mid-Holocene)? Methods The study was carried out in 14 Atlantic rainforest sites in Brazil (20.4 ha sampled) containing 615 tree species from 83 plant families. We obtained plot-level geographic coordinates and soil variables and site-level bioclimatic variables in the current, Mid-Holocene, and Last Glacial Maximum. We used structural equation models (SEM) with a distance-based approach to (i) test the direct effects of spatial distance and environmental dissimilarity, and (ii) test the indirect effects of spatial distance via environmental dissimilarity on taxonomic (Bray-Curtis distance) and phylogenetic turnover (Comdist and Comdistnt distances). Important Findings Our results suggest a weak indirect effect of spatial distance via environmental dissimilarity on taxonomic and phylogenetic turnover. Tree community turnover was driven by the direct effects of neutral, niche-based and historical processes. Thus, we inferred that the paleoclimate (historical processes) promoted the selection of the clades that gave rise to the current flora, while spatial distances (neutral processes) limited the dispersal range of species from the regional pool and environmental conditions (niche-based processes) locally selected the taxa that are able to persist.

Fragmentation is one of the main causes of biodiversity loss in tropical forests through consequences on their different components. Beta diversity patterns across fragments have been studied across multiple spatial scales, but comparisons with intact landscapes and in a variety of vegetation types are scarce. In order to address this issue of anthropogenic landscape disturbance, we tested two hypotheses relating to fragmentation and beta diversity: 1. Floristic homogenization at patch-level scale and 2. Floristic differentiation at landscape-level scale. The study was conducted in the Espinhaço Range biosphere reserve, Brazil. Three landscapes encompassing a broad range of vegetation types were sampled in 115 plots. Two landscapes were fragmented due to mining activities (Sabará and Brumadinho) and one is protected (Parque Estadual Serra do Rola-Moça). Results showed high overall beta diversity both between landscapes (conserved and fragmented) and vegetation types (forest, Brazilian savanna "campos rupestres", ecotone and ironstone "canga") with high turnover and species losses, even in highly disturbed vegetation types. The conserved landscape was most diverse in terms of richness. Thus, fragmentation effects differed from the expected with a main role of differentiation processes, and we argue that high beta diversity is not always a good predictor of ecosystem health.

Flood forests are vegetation subject to seasonal floods. Situated in flood plains, they are systems under continuous changes due to the pulses of flooding, following the watercourse. Although these are singular ecosystems, there are little publications that report the floristic structure in floodplains, especially in Southeastern Brazil. This study aimed to characterize the composition, structure and diversity of the arboreal community in a flooding gradient, comparing them with the non-flood adjacent formations, at the mouth of Paracatu River, a tributary of São Francisco River, Minas Gerais, Brazil. For the structural survey of the arboreal community, we used the plot method, installed on both sides of Paracatu River. The individuals were identified at the species level. We sampled 1,276 individuals belonging to 85 species and 32 families. The Shannon Index (H`) regarding to the total sampling was of 3.40 nat.ind, with Pielou evenness index (J`) of 0.76. In terms of species importance, the six most important species comprised 46% of the total index of importance value. By means of similarity analysis, it was possible to verify the grouping of species along the ecounits, demonstrating the substitution of species along habitats, resulted of the temporal difference of the flooding in the environments. In conclusion, the flooding regimes, frequency and intensity determine the ecology of the river plains.

Flood forests are vegetation subject to seasonal floods. Situated in flood plains, they are systems under continuous changes due to the pulses of flooding, following the watercourse. Although these are singular ecosystems, there are little publications that report the floristic structure in floodplains, especially in Southeastern Brazil. This study aimed to characterize the composition, structure and diversity of the arboreal community in a flooding gradient, comparing them with the non-flood adjacent formations, at the mouth of Paracatu River, a tributary of São Francisco River, Minas Gerais, Brazil. For the structural survey of the arboreal community, we used the plot method, installed on both sides of Paracatu River. The individuals were identified at the species level. We sampled 1,276 individuals belonging to 85 species and 32 families. The Shannon Index (H`) regarding to the total sampling was of 3.40 nat.ind, with Pielou evenness index (J`) of 0.76. In terms of species importance, the six most important species comprised 46% of the total index of importance value. By means of similarity analysis, it was possible to verify the grouping of species along the ecounits, demonstrating the substitution of species along habitats, resulted of the temporal difference of the flooding in the environments. In conclusion, the flooding regimes, frequency and intensity determine the ecology of the river plains.