Size‐dependent species removal impairs ecosystem functioning in a large‐scale tropical field experiment

Abstract

A major challenge of ecological research is to assess the functional consequences of species richness loss over time and space in global biodiversity hotspots, where extinctions are happening at an unprecedented rate. To address this issue, greater realism needs to be incorporated into both conceptual and experimental approaches. Here we propose a conceptual model that incorporates body size as a critical aspect of community responses to environmental change, which we tested in the Western Amazonian rain forest, one of the most speciose ecosystems on the planet. We employed an exclosure removal experiment (replicated under 10 microhabitats and four climatic conditions) in which we manipulated access to two types of resource by the whole community of dung and carrion beetles (> 60 species), depending on their size. Our 400 independent measurements revealed that changes in the number of species and functional groups, and temporal patterns in community composition, all affected resource burial rates, a key ecosystem process. Further, the functional contribution of species diversity in each size class was tightly dependent on beetle abundance, and while the role of large species could be performed by abundant smaller ones, and other naturally occurring decomposers, this was not the case when environmental conditions were harsher. These results demonstrate, for the first time in an animal assemblage in a tropical ecosystem, that although species may appear functionally redundant under one set of environmental conditions, many species would be needed to maintain ecosystem functioning at multiple temporal and spatial scales. This highlights the potential fragility of these systems to the ongoing global "Sixth Great Extinction," whose effects are likely to be especially pronounced in the Tropics.

Phylogeny as a Proxy for Ecology in Seagrass Amphipods: Which Traits Are Most Conserved?

“…As discussed above, phylogenetic distance is a poor proxy for complementarity in feeding niche, and therefore unlikely to predict whether a community of mesograzers is able to perform the key function of removing multiple types of algal competitors to promote seagrass growth (see for example [86]). The very strong phylogenetic signal in body mass, however, could link phylogeny to ecosystem function because large species frequently have large impacts on function [4], [87], [88]. For example, we have found that the presence or absence of the largest amphipod in our system ( Ampithoe lacertosa ) can have a much larger impact on algal abundance than the resource complementarity of the grazer community [82].…”

Dung Beetles Associated with Agroecosystems of Southern Brazil: Relationship with Soil Properties

“…These characteristics suggest that D. nisus is the species that most contributes to the nutrient cycling process and organic matter mineralization in this environment. Species in the paracoprid (tunneler) functional group often have large body size, making them more efficient and capable of greater removal of fecal matter (Slade et al, 2007;Dangles et al, 2012). Furthermore, this species favors the soil aeration process through the digging of tunnels for resource storage and use.…”

Variations in dung beetle assemblages across a gradient of hunting in a tropical forest

“…The disappearance and decreasing abundance of large paracoprid species have a large impact on several ecological processes because they are the beetles that bury the most dung (Dangles et al, 2012). A loss of nutrient cycling and secondary seed dispersal is expected (see Braga et al, 2013).…”