Abstract

Our study evaluated the effects of environmental factors and ecological integrity on the communities of semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) in Cerrado (= Brazilian savanna) streams. We tested the following predictions: (i) altered streams will show a decreased level of environmental heterogeneity at regional scales; (ii) there will be a greater number of specialist species in preserved streams; (iii) Gerromorpha communities are structured mainly by local environmental factors of the streams; and (iv) alpha and beta diversities are higher in preserved streams, and altered streams contribute less to regional diversity. To test for that, we sampled semiaquatic bugs and environmental variables in 20 streams located on the northern portion of the Cerrado biome, in a 50 m transect in each site. Initially, we observed that environmental heterogeneity was higher among altered streams, contradicting our expectation. This result was supported by the finding that alpha and beta diversities of semiaquatic bugs were higher in altered streams. We also found that the environment explained 18% of the variation in Gerromorpha communities, while space explained about 23% of this variation. Our work shows a strong association between community structure and local environment, independent of the conservation status of the streams. Furthermore, because the study area lies in an Amazon–Cerrado–Caatinga transitional zone, it contains species from all these biomes, which are highly associated with space, indicating that community structuring can also occur due to biogeographic factors. Finally, this study contains relevant information concerning the aquatic biodiversity from the region that can be used to formulate conservation strategies for the Cerrado, a highly threatened biome.

Implications for insect conservation

Our work shows how habitat disturbances in streams can change Gerromorpha communities, especially in relation to the environmental heterogeneity. Furthermore, because the study area lies in an Amazon–Cerrado–Caatinga transitional zone and species are highly associated with space, community structuring can also occur due to biogeographic factors. Information contained in this study can be used to formulate conservation strategies for the Cerrado, the second largest biome of Brazil in extension and currently the most threatened one.