Abstract
The role of deterministic and stochastic mechanisms in community assembly is a key question in ecology, but little is known about their relative contribution in dung beetle assemblages. Moreover, in human modified landscapes these mechanisms are crucial to understand how biodiversity can be maintained in productive agroecosystems. We explored the assembly mechanisms driving dung beetle assemblages in forests and grazed grassland patches, and assessed the role of dung availability, soil hardness and moisture, elevation and land use heterogeneity as environmental predictors of functional diversity. To determine the underlying assembly mechanisms, we estimated functional diversity metrics (functional richness, evenness and divergence) and their departure from the predicted values by null models. We also used GLMs to assess the influence of environmental variables on functional diversity. In most cases, stochastic processes prevailed in structuring dung beetle assemblages and, consequently, environmental variables were not good predictors of dung beetle functional diversity. However, limiting similarity was found as a secondary mechanism with an effect on dung beetle assemblages in grasslands. Our results highlight the importance of stochastic processes that may reflect a metacommunity dynamic. Therefore, restoring landscape connectivity might be more important than habitat quality for the conservation of these functionally diverse beetle assemblages.
Highlights
The role of deterministic and stochastic mechanisms in community assembly is a key question in ecology, but little is known about their relative contribution in dung beetle assemblages
Community assembly theory provides a conceptual foundation about the mechanisms that determine species composition of local assemblages[1,2], and this background becomes especially relevant for studies concerning the ecological consequences of environmental contemporary changes
Results from a recent study have made it possible to improve our understanding of biological invasions, a global issue that is critical in ecology and conservation[3]
Summary
The role of deterministic and stochastic mechanisms in community assembly is a key question in ecology, but little is known about their relative contribution in dung beetle assemblages. Identifying the drivers of community assembly in human modified landscapes is an urgent challenge Both deterministic and stochastic mechanisms are important in assembling biological communities. Our ability to understand the relative importance of these not mutually exclusive assembly mechanisms is critical, as they can have high impacts on the conservation of local biodiversity and ecological functions. Recent studies on ground-dwelling beetles have incorporated the analysis of functional traits to assess forest-grassland gradients[18] and community assembly rules[19]. Because they are related to species’ niches, the variability of those traits within communities (i.e., functional diversity) is assumed to reflect the imprint of assembly mechanisms such as environmental filtering or competitive interactions. If the observed functional diversity is not different from the expected in a null model of random assembly, stochastic processes are assumed
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