Habitat modification and alpha-beta diversity in trap nesting bees and wasps (Hymenoptera: Aculeata) in southern Brazil

The global decline in biodiversity has been mainly attributed to the expansion of agricultural areas that transform continuous forest ecosystems into mosaic landscapes of simple agricultural and natural forest fragments. Considering this, the objective of this research was to evaluate if habitat modification affects trap nesting bees and wasps richness and abundance. An assemblage of bees and wasps that nest in pre-existing cavities was studied. The tested hypothesis was that species composition, richness and evenness are affected with habitat modification. Trap nests with different diameters were used to capture these insects in forests and in organic fields in Southern Brazil. Species composition in these areas was different, which led to the acceptance of the hypothesis that it is affected with habitat modification. The opposite occurred with alpha diversity because there was no significant difference between the richness of these areas. The most abundant genus, both in the forest areas and in the growing areas, was Trypoxylon, suggesting that the degree of impact on the Araucaria forest fragments is one of the factors that makes the diversity of these areas similar (in addition to the organic fields) since wasps of this genus usually occur in impacted areas.