Tropical forest dung beetle–mammal dung interaction networks remain similar across an environmental disturbance gradient

Abstract

1. Conservation outcomes could be greatly enhanced if strategies addressing anthropogenic land-use change considered the impacts of these changes on entire communities as well as on individual species. Examining how species interactions change across gradients of habitat disturbance allows us to predict the cascading consequences of species extinctions and the response of ecological networks to environmental change.2. We conducted the first detailed study of changes in a commensalist network of mammals and dung beetles across an environmental disturbance gradient, from primary tropical forest to plantations, which varied in above-ground carbon density (ACD) and mammal communities.3. Mammal diversity changed only slightly across the gradient, remaining high even in oil palm plantations and fragmented forest. Dung beetle species richness, however, declined in response to lower ACD and was particularly low in plantations and the most disturbed forest sites. Three of the five network metrics (nestedness, network specialization and functionality) were significantly affected by changes in dung beetle species richness and ACD, but mammal diversity was not an important predictor of network structure. Overall, the interaction networks remained structurally and functionally similar across the gradient, only becoming simplified (i.e. with fewer dung beetle species and fewer interactions) in the most disturbed sites.4. We suggest that the high diversity of mammals, even in disturbed forests, combined with the generalist feeding patterns of dung beetles, confer resilience to the commensalist dung beetle-mammal networks.

Mammal dung–dung beetle trophic networks: an improved method based on gut-content DNA

“…Furthermore, in the German temperate forest, we see less overlap in dung beetle diets than would be expected by random dung choice, under the expectation that dung beetles are generalist dung consumers ( Hanski & Cambefort, 1991 ; Nichols et al, 2009 ; Frank et al, 2018a ). Rodents were more dominant in the German mammal dung–dung beetle network than expected based on previous conclusions from the research of mammal dung–dung beetle networks ( Hanski & Cambefort, 1991 ; Nichols et al, 2008 ; Frank et al, 2018a ; Raine & Slade, 2019 ; Chiew et al, 2022 ). Previous research suggested that German networks are dominated by wild boar and deer, among other medium and large-bodied mammals, while rodents were mostly missing.…”

“…For instance, there are some direct feeding observations at dung piles, but this is likely biased towards larger, more obvious dung, such as that from elephants, cows, and humans ( Young, 1981 ; Hanski & Cambefort, 1991 ; Scholtz, Davis & Kryger, 2009 ). Further, experimentally deployed dung often represents common or readily available species, even using non-native species from zoos ( Hanski & Cambefort, 1991 ; Frank et al, 2018a ; Raine & Slade, 2019 ; Chiew et al, 2022 ). Overall, this has often led to the assumption that dung beetles primarily consume dung from large- and medium-sized mammals ( Hanski & Cambefort, 1991 ; Scholtz, Davis & Kryger, 2009 ; Simmons & Ridsdill-Smith, 2011 ; Bogoni & Hernández, 2014 ; Frank et al, 2018a ; Frank et al, 2018b ; Raine et al, 2018 ; Raine & Slade, 2019 ; Bogoni, Da Silva & Peres, 2019 ).…”

“…This approach has then been passed on to the realm of mammal dung-dung beetle networks ( Frank et al, 2018a ; Raine & Slade, 2019 ; Chiew et al, 2022 ; Pryke, Roets & Samways, 2022 ). For example, rodent dung is often excluded from cafeteria-style experiments or other dung attraction experiments designed to study mammal dung-dung beetle networks ( Bogoni & Hernández, 2014 ; Frank et al, 2018a ; Raine & Slade, 2019 ; Ong, Slade & Lim, 2020 ; Chiew et al, 2022 ; Pryke, Roets & Samways, 2022 ). Traditional methods of creating mammal dung–dung beetle networks might thus be biased.…”

Bait attractiveness changes community metrics in dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae)

“…Pitfall traps baited with fecal material clearly remain a valid, useful, and efficient tool for dung beetle surveys, providing reliable capture success for species that feed on feces. Their use in biodiversity surveys and ecological studies has been increasing over the past 30 years (Raine & Slade, 2019 ), many of which focus on dung beetle assemblage metrics (Bogoni et al, 2019 ; Chiew et al, 2021 ; Enari et al, 2018 ; Fuzessy et al, 2021 ; Nependa et al, 2021 ), and dung beetle‐mammal interaction networks (Nichols et al, 2009 ; Raine et al, 2018 ). Clearly, it is not our intention to reject a widely established and broadly accepted sampling protocol for the dung beetle field studies.…”

Importance of restoration of dung beetles in the maintenance of ecosystem services

“…Without sufficient providers of this habitat, the abundance and richness of dung beetles will be low (Buse et al., 2021). Dung beetle species richness is positively correlated with mammal biomass (Culot et al., 2013), and high diversity of native mammals enhances the resilience of dung beetle–mammal networks (Chiew et al., 2022), leading to increased abundance, richness and diversity of dung beetles (Amézquita & Favila, 2010; Buse et al., 2021; Nependa et al., 2021). Additionally, the abundance of dung beetles may be related to native burrowing mammals (Lindtner et al., 2019) due to their effects on soil structure and interspecies facilitative or commensal relationships.…”