Assemblage and functional categorization of dung beetles (Coleoptera: Scarabaeinae) from the Pantanal

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

The Influence of Fine-Scale Grazing Heterogeneity on Dung Beetle Assemblages: What Trait Analysis Teaches Us

Livestock grazing puts major anthropogenic pressure on biological communities worldwide. Not all species are expected to be affected in the same way, and the impacts will depend on species' traits. Focusing on traits thus helps identify the mechanisms underlying changes in community composition under grazing pressures. We investigated how fine-scale grazing heterogeneity affects the trait composition and diversity of dung beetle assemblages in Western Europe. We sampled dung beetles in habitat patches differing in terms of grazing intensity within rangelands of two distinct biogeographical areas: a Mediterranean lowland steppe and Western alpine meadows. We measured five morphological traits expected to respond to the local-scale filtering pressure exerted by variations in grazing intensity. Using individual-based data, we assessed responses in terms of single-trait mean values in communities and complementary trait diversity indices. We found strong shifts in trait composition and diversity between the habitat patches. In both study areas, variations in habitat conditions are likely to have filtered the local occurrence and abundance of dung beetles by the mean of traits such as body mass (which have several functional implications), as well as traits linked to underground activity. We hypothesize that fine-scale variation in resource availability (i.e., droppings) and disturbance intensity (i.e., trampling) are key drivers of the observed patterns in species assemblages. Trait richness peaks at moderate grazing intensity in both study areas, suggesting that patches with an intermediated level of available resources and soil disturbance enable individuals with a greater range of autecological requirements to coexist.

Can taxonomic and functional metrics explain variation in the ecological uniqueness of ecologically-associated animal groups in a modified rainforest?

The conservation of biodiversity requires adequate information about species and ecosystem attributes. The local contribution to β-diversity (LCBD) is a community composition-based metric of ecological uniqueness of sites. Here, we tested the capability of taxonomic and functional attributes of biological communities to explain variation in LCBD at a large spatial extent. We approached this idea using data on dung beetles and mammals (medium-to-large, small and volant) recorded across the Atlantic Forest of South America due to their millennial-scale evolutionary relationship (food providers and consumers). We related LCBD values to both taxonomic and functional metrics via beta regression. Our results revealed that taxonomic and functional features of assemblages can be used to predict variation in ecological uniqueness (LCBD). High LCBD values were associated with low species and functional richness for all animal groups. For dung beetles, high LCBD values were associated with low values of all functional metrics. For mammalian groups high ecological uniqueness was associated with low abundance, low Rao's quadratic entropy, as well as high functional divergence, functional evenness, functional originality, and either low or high functional specialization. This implies that variation in ecological uniqueness can be explained by functional features at large spatial extents, although the type of functional metrics' response of assemblages may be animal group specific. The potential of the LCBD metric to inform about both taxonomic and functional changes at large scales makes its use in conservation planning a highly promising approach.