Interactions between land use, taxonomic group and aspects and levels of diversity in a Brazilian savanna: implications for the use of bioindicators.
Abstract
The conversion of natural habitats into anthropogenic uses is a key driver of global biodiversity loss, but effects can vary among taxa and diversity metrics. This has important implications for the use of bioindicators in land management. We evaluated the local-scale responses of multiple faunal taxa to land-use change in the Brazilian Cerrado measuring different aspects (taxonomic and functional) and levels (alpha and beta) of diversity. We compared ant, dung beetle and bird assemblages inhabiting remnants of natural habitat (savanna and semi-deciduous forest) with those found in cattle pastures, soy fields or Eucalyptus plantations. Species richness was markedly higher in natural habitats for ants and birds but not for dung beetles. Effects on functional alpha diversity were taxon specific and there was not such a contrast between natural and anthropogenic habitats. Patterns of functional beta diversity were correlated with patterns of taxonomic beta diversity and were also taxon specific. For dung beetles, site-to-site variation in taxonomic and functional composition was greatest in forests, whereas birds tended to present greater spatial turnover and ants greater nestedeness in the anthropogenic than in the natural habitats. Among the three anthropogenic land uses, tree plantations presented the most similar composition to natural habitat for all taxa. Overall, similarity in taxonomic and functional composition between natural and anthropogenic habitats was greater for savanna than forest. Synthesis and applications. The responses of ant, dung beetle and bird assemblages to land-use change in the Cerrado were highly variable. Nonetheless, results indicate that the extent of impacts on biodiversity reflects the extent of habitat transformation and that impacts at a landscape scale may be reduced by a mix of land uses. We showed that effects were more severe from a taxonomic than from a functional perspective, for the forest than for the savanna-associated fauna, for the ant and bird than for the dung beetle fauna, and often in lands devoted to intensive agriculture rather than to pastoralism or plantation forestry. Our findings can help guide the selection and assessment of indicator taxa and the interpretation of exactly what they are indicating.