AIMS: Investigated how the loss of environmental integrity affects damselfly species composition in nine sites with different levels of environmental integrity in a Cerrado-Amazon transition region known as "arc of deforestation" in Mato Grosso State, Brazil. We also tested the influence of environmental variables on species composition. METHODS: We collected in transects of 100 m and used ordination (PCoA) and simple linear regression. RESULTS: Species composition was strongly influenced by the environmental quality of sites, and the best model to explain species composition included variables related to channel morphology. CONCLUSIONS: These results are connected to the environmental homogenization and loss of environmental integrity as a result of extensive agricultural practices which alter stream communities of dragonflies in this region.

Abstract:We compared the diversity and species composition, and the structure of the vegetation of three distinct Cerrado phytophysiognomies (Cerradão, Dense Cerrado, and Typical Cerrado)

Our goal was to investigate whether the loss of riparian forests alters the structure of assemblages and populations of dragonflies and damselflies. We tested the hypothesis that the composition of the odonate assemblages found upstream from dams are significantly different from those found downstream of these barriers. To test the hypothesis, we investigated stream sectors upstream and downstream of three dams located at the extreme of the southern Amazon basin, in the Brazilian state of Mato Grosso. We collected 111 adult odonates, 45 upstream and 69 downstream, representing 18 species, 12 upstream and 10 downstream. The most abundant species was Epipleoneura williamsoni Santos, 1957 (n = 41, 36.9%), followed by Epipleoneura metallica Rácenis, 1955 (n = 20, 18%) and Hetaerina curvicauda Garrison, 1990 (n = 17, 15.3%). Statistical ordination separated the different sectors, with the greatest dissimilarity being found between the upstream and downstream I (DS I), and our hypothesis was further supported by the fact that six of the 18 species recorded in the study did not occur in the upstream sector. As this process may lead to the local extinction of part of the biodiversity of the Amazon-Cerrado transition, even before it is fully understood, we would recommend that the observed pattern be verified through the analysis of other taxonomic groups and on a more ample spatial scale.

We surveyed two savanna sites, one on fl at terrain with deep soil (DS), and the other on hilly terrain with rocky outcrops and shallow soil (RS), before and after an accidental fi re. We found that the fi re did not cause any signifi cant changes in the species composition or diversity of either community, and did not result in fl oristic homogenization. However, we did record a reduction in the density of plants and in basal area in the DS savanna in comparison with the RS savanna, as well as a higher rate of basal sprouting, which indicates a trade-off between mortality and sprouting. We conclude that, whereas post-fi re changes in vegetation structure were more pronounced in the DS savanna than in the RS, the diff erence in the underlying substrate did not have a direct infl uence on the post-fi re composition of woody species. Th e greater grass biomass found in the DS savanna in comparison with the RS savanna appears to have been the principal modulator of the severity of the fi res in the two phytophysionogmies, and accounts for the distinct responses to fi re we observed in the two woody communities.

We investigated the existence of an ecotone in the species composition, diversity and vegetation structure in the transition between gallery forest and cerrado sensu stricto in central Brazil. We tested two hypotheses: 1) a ecotone can be found between gallery forest and cerrado; 2) a gradient exists in the species composition of the cerrado. We established three parallel transects of 5 m × 350 m running between gallery forest and cerrado, which were divided into subplots of 5 m × 10 m, perpendicular to the margin of the Bacaba stream in Nova Xavantina (Mato Grosso, Brazil). We identified and measured the height and diameter of individual plants in the plots with a diameter of at least 3 cm at 30 cm above the ground. We recorded 140 species, of which 26 were exclusive to the gallery forest, and 95 to the cerrado. The cerrado presented higher species richness (observed and estimated) and diversity (diversity profiles) than the gallery forest. Both hypotheses were accepted: a distinct ecotone was observed between gallery the forest and cerrado, and a pronounced gradient was found in species composition among the cerrado plots, apparently in response to the variation in soil moisture content, probably related to topography.