Efeitos da estrutura da paisagem e da simplificação de habitat sobre assembleias de abelhas e vespas solitárias

Abstract

Bees and wasps constitute an essential biological group for most terrestrial ecosystems, both for natural ecosystems and for agricultural environments. Bees are important pollinator to most angiosperms species, while wasps are predators and may act in the pest control. However, bees and wasps are very sensitive to environmental change, especially the solitary bees and wasps that nest in pre-existing cavities. Therefore, a concern about its decline is growing around the world. As major reported causes affecting the diversity, species richness and mortality of bees and wasps are the changes in natural habitat. However, because of its large movement capacity, it is important to assess how changes in its habitat both at local scales and at landscape scales. The main goal of this study was to understand how environmental changes in different scales affect the diversity and mortality of bees and wasps and their parasitoids. In Chapter 1, we measured the effects of local habitat simplification on species richness and spatial patterns of diversity and their components. We also analysed the changes in species composition along a habitat structural gradient. We have shown that the habitat simplification has a negative effect on bees and wasps diversity and these effects are stronger in naturally more complex habitats. In chapter 2, we studied the effects of natural vegetation loss and the composition and configuration of environments at the landscape level on the diversity of bees, wasps and their parasitoids. We have shown that landscape heterogeneity affected bees and wasps differently. While bees responded negatively to configurational heterogeneity, wasps benefited from landscapes with more irregular patches. In chapter 3, we analyzed the effects of landscape structure on mortality and development time of bees and wasps and showed that the landscape shape and the agriculture proportion decreased the mortality and influenced the causes of death. In summary, the results showed that habitat simplification, at both local and landscape scale, affects the diversity of these insects. However, an adequate landscape management can mitigate these effects by providing additional resources for bees and wasps.