Functionally richer communities improve ecosystem functioning: Dung removal and secondary seed dispersal by dung beetles in the Western Palaearctic

Abstract

Aim In several ecosystems, the diversity of functional species traits has been shown to have a stronger effect on ecosystem functioning than taxonomic diversity alone. However, few studies have explored this idea at a large geographical scale. In a multisite experiment, we unravelled the relationship between ecosystem function and functional completeness of species assemblages using dung beetles as a model group, focusing on dung removal and secondary seed dispersal. Location Seventeen grassland locations across the Western Palaearctic. Methods We used a randomized block design with different exclosure types to control the dung and seed removing activities of individual functional groups of the local dung beetle assemblage. We classified dung beetle species according to resource specialization and into functional groups based on dung processing behaviour (dwellers, tunnellers, rollers) and body size (small, large). Additionally, we assessed the role of other soil macro‐invertebrates. By sampling the dung beetle community and measuring the remaining dung and seeds after the experiment, the impact of each functional group was estimated. Results Dung beetle assemblages differed along a north–south and east–west gradient. Dwellers dominated northernmost sites, whereas at lower latitudes we observed more tunnellers and rollers indicating a functional shift. Resource specialists were more abundant in southern and eastern areas. Overall, functional group diversity enhanced dung removal. More dung (+46.9%) and seeds (+32.1%) were removed in the southern sites and tunnellers and rollers were more effective. At the northernmost sites, where tunnellers were scarce or absent, other soil macro‐invertebrates removed the majority of dung. Main conclusions The conservation of functionally complete dung beetle assemblages is crucial to maintain the ecosystem functions provided by dung beetles. Given the latitudinal variation in functional group diversity, it is reasonable to expect compositional changes due to climate change. These changes could lead to increased dung removal and a higher secondary seed dispersal rate in northern regions.

Stronger dung removal in forests compared with grassland is driven by trait composition and biomass of dung beetles

“…This is in accordance with other experiments carried out in tropical and boreal habitats and shows the general importance of tunnellers for ecosystem functioning (Slade et al ., ; Kaartinen et al ., ). This is particularly the case for most Central European regions where roller species are absent and tunnellers are the most effective group from a functional perspective (Milotić et al ., ). In our experiment, tunneller biomass varied up to 165‐fold between locations in autumn and up to 315‐fold in summer.…”

“…There were only weak effects of species richness, abundance, and no effect of functional diversity on dung removal in the habitats studied, although positive relationships were reported from mesocosm experiments and from field studies elsewhere (Slade et al ., ; Beynon et al ., ; Dangles et al ., ; Gollan et al ., ; Milotić et al ., ). However, mesocosm experiments with species from temperate habitats showed that the loss of abundance has a larger effect on dung removal than did species loss (Manning & Cutler, ).…”

“…Nesting strategy is a combination of body size [large (>10 mm) vs. small (< 10 mm); cf. Milotic et al ., ] and nesting behaviour (tunneller, dweller). There were no roller species in the study site.…”

Forest complexity drives dung beetle assemblages along an edge‐interior gradient in the southwest Amazon rainforest

“…To preserve dung beetle assemblages and their ecosystem functions, conservation strategies in tropical forests should prioritise reduction in deforestation or logging and an increase in the environmental heterogeneity (Sánchez-de-Jesús et al, 2016;Edwards et al, 2017). Sensitive management will increase biological diversity and hence functional diversity as a result of habitat adaptation or habitat preference of species to different environments (Milotić et al, 2019). In the FEA, a managed logging forest, caution should be taken to avoid the occurrence of clearings close to logging areas (Edwards et al, 2017) because both have strong effects on the forest and biodiversity.…”

“…Consequently, environmental changes strongly affect the performance of their ecological functions (Braga et al, 2013;Gray et al, 2014). However, there is functional importance with respect to maintaining a species-rich dung beetle assemblage even in the absence of perturbations to the system, which is expected to buffer ecosystem services in disturbed ecosystems (Beynon et al, 2012;Milotić et al, 2019). The habitat specificity found in dung beetles prevents several forest-dependent species to inhabit open habitats (Klein, 1989;Noriega et al, 2007;Silva et al, 2016) as a result of changes in microclimatic conditions along the open-forest habitat gradient (Feer, 2008).…”