Biodiversity in landscape mosaics: the roles of local land use and the surrounding landscape on dung beetle assemblages.
Abstract
Biotic communities in heterogeneous agricultural landscapes can be shaped by both the land use of local patches and the structure of surrounding landscapes. However, studies usually focus on one or the other factor, limiting our ability to propose management guidelines for the conservation of biodiversity in human-modified landscapes. We used a site-landscape design and multi-model inference to assess the effects of land use, landscape structure, and their interactions, on dung beetle assemblages in agricultural landscapes in the Brazilian Cerrado, a biodiversity hotspot. We captured dung beetles in five dominant land uses (savanna, forest, eucalypt, cattle pasture and soybean) and estimated species density, abundance of large and small beetles, and functional richness and dispersion. We measured four landscape structure predictors (savanna cover, forest cover, landscape compositional heterogeneity, and matrix harshness) in circular landscapes around sampling plots. All response variables were affected by land use and by at least one landscape predictor. Relationships between landscape predictors and dung beetle responses were as expected (positive for forest and savanna covers and negative for matrix harshness), except landscape compositional heterogeneity, which had unexpected negative effects. More importantly, land use and landscape predictors interacted in two cases: higher forest cover and lower matrix harshness were related to higher species density and large-beetle abundance, respectively, but this was mainly observed in eucalypt. Synthesis and applications: To better guide the conservation of mobile organisms in anthropogenic habitat mosaics, we need to consider both landscape characteristics and the land use of local patches. Using this approach, we are able to make some recommendations for the conservation of dung beetles in agricultural landscapes in Cerrado, including the following: (i) ensure, through protection and/or restoration, that natural vegetation patches (even small ones) are interspersed in the agricultural matrix, to increase functional diversity in all land uses and taxonomic diversity in tree plantations, (ii) place eucalypt plantations near forest patches to increase the abundance of sensitive species (forest-specialists, and some large species); (iii) replace some patches of pasture or soybean with tree plantations, to increase the amount of supplementary habitat for sensitive species.