Efeitos da agricultura intensiva da soja e perda de hábitat nas assembleias de abelhas, Nordeste do Brasil

Abstract

Habitat loss by human activities is the main threat to biodiversity, especially for bees that are essential for agricultural yield and ecosystem maintenance. In the Neotropical region, the effects of anthropization on bee assemblages are poorly understood, as in many regions the fauna is still unknown and the studies performed were predominantly on Euglossini. Understanding how anthropization affects the distribution of species and the resources needed for survival is key to designing strategies for conservation and management. In this context, this work evaluated bee assemblages in Caatinga and Cerrado fragments that make up the landscape of the Parnaíba / Gurguéia interfluve, southwest of the State of Piauí, northeastern Brazil. The first study analyzed the effects of soybean fields on bee assemblages in Cerrado Legal Reserve, and the second, compared the assemblages between two Caatinga fragments, close to each other. The bees were collected from August 2015 to August 2016, using odoriferous traps and pan trap along transects. The assemblages were analyzed for abundance, richness and rates of taxonomic (Hill and Simpson N1) and functional (RAO index) diversity, as well as comparisons for beta diversity and/or dendrograms of similarity. Functional traits were also evaluated on feeding behavior, nesting substrate, type of vegetation for nesting/breeding, degree of sociability/parasitism and body size, in order to identify the most vulnerable species to the effects of habitat loss. In the Caatinga fragments, differences were observed in seasonality, diversity and composition among the 18 species registered. Caatinga habitat loss has proved to affect cleptoparasites, Xylocopini and Emphorini species, which have a restricted niche. In the Cerrado, soybean fields reduced 79.5% the dispersion capacity of the 76 species recorded in the Cerrado fragments, and the most vulnerable species to local extinction were the cleptoparasites, the oligolectics, and those that require trunks as nesting substrate. Beta diversity differed by 80%, indicating a marked loss of species in the sites evaluated due to the expansion of crop fields. Both studies increased the knowledge of the distribution of several species and found 21 new species, being 17 in the Cerrado and four in the Caatinga.