The emerging threat of pollinator declines has motivated research on bee ecology to understand the causes of declines and to develop appropriate conservation strategies. The main drivers of decline are anthropogenic and include: loss of habitat to agricultural intensification; use of pesticides; climate change; and alien species. However, in many parts of the world, knowledge of bee ecology and spatial distributions is scarce and the impacts of these stressors on bee populations are poorly understood. The Iberian Peninsula, located in the south-western part of Europe is one of the regions in Europe where there is large knowledge gap in relation to bee distribution and their conservation status. Additionally, the region has experienced the expansion of farmland abandonment in remote areas due to poor soils and rural depopulation. This thesis investigates how bee distributions in the Iberia Peninsula are shaped by climate using innovative tools such as Species Distribution Modelling (SDMs). It also evaluates how farmland abandonment shapes bee communities and their ecological interactions along an environmental gradient. The main findings reveal a) the climatic distributions of bumblebees, highlighting under-sampled areas in Iberia where rare species are likely to occur; b) the negative effect of land abandonment on bees in the intermediate successional stages such as shrublands; c) great beta diversity, with higher differences in species composition between sites (ßRepl) in early-successional stages such as grasslands d) plant-bee interactions become more specialized along a secondary succession triggered by land abandonment. Overall, this thesis provides novel information on the ecology of bees and proposes the best management practices for Iberian bee conservation including the need to control the proliferation of intermediate successional stages in the landscape while preserving grasslands and forests
