Effects of the conversion of neotropical savannas into pastures on dung beetles biodiversity and their ecological functions

Abstract

The replacement of natural systems caused by the expansion of agriculture and livestock has been the main driver of biodiversity in tropical regions. Associated to the land use changes, the climate change are having a strong impact on biological system and may altered the biodiversity distribution and interactions. It is estimated that one-fifth of the world's population live in tropical savannas regions and depends directly on these systems, making than one of the most impacted ones. The Brazilian Cerrado is the largest, richest tropical savannah, with a high rate of endemism, however it has been extensively cleared for agriculture and livestock. The group of organisms of dung beetles are sensitive to climate changes, since climate has direct influence on their life cycle. Besides, these beetles has been widely used as bioindicator since they show habitat specificity and respond to changes in environmental conditions. Due so, both climate changes and disturbances in natural systems may affect dung beetle communities, changing the habitat associations and reducing the rates of dung removal and the associated functions. Here, we aim to understand how conversion of savannah into pasture affects biodiversity and ecosystem functioning using dung beetles as a study group. We also assessed climatic and environmental variables to test their direct and indirect effects on dung beetle communities and associated ecological functions dung removal, soil bioturbation, and dung beetles interaction with dung-feeding fly. To do these, we selected experimental study areas of Cerrado and exotic cattle pastures in different municipalities in the state of Minas Gerais, Brazil. We found that conversion of savanna into pasture has a negative effect on both taxonomic and functional diversity metrics, causing loss of species richness, functional richness and equitability. We also found that Cerrado conversion into pasture can have a cascade effect, as the loss of vegetation cover leads to loss of dung beetle species richness, which causes loss of biomass and functional indices, affecting dung beetle functions and interaction with dung flies. However, the effect of land use changes in tropical savannas is dependent of the bioclimatic zones. Our results showed the importance of Cerrado habitat for biodiversity and the maintenance of ecosystem functioning, and we suggest that pubic politics should be thought to evaluate separately each region, submitted to the effects of different bioclimatic conditions, since the responses of dung beetles communities are context dependent.