Co‐declining mammal–dung beetle faunas throughout the Atlantic Forest biome of South America

Abstract

The millennial-scale evolutionary relationships between mammals and dung beetles have been eroded due to several drivers of contemporary biodiversity loss. Although some evidence of co-decline has been shown for mammals and dung beetles at some Neotropical sites, a biome-scale analysis for the entire Atlantic Forest of South America would strengthen our understanding of how relictual sets of mammal species can affect dung beetle co-occurrences and co-declines. We therefore collated hundreds of assemblages of both dung beetles and medium-to large-bodied mammals throughout the world's longest tropical forest latitudinal gradient to examine to what extent mammal assemblages may exert a positive influence on dung beetle species composition and functional assembly, and whether this relationship is scale dependent. We also collated several climatic and other environmental variables to examine the degree to which they shape mammal-dung beetle relationships. The relationships between local mammal and dung beetle faunas were examined using regression models, variation partitioning, dissimilarity indices and ecological networks. We found a clear positive relationship between mammal and dung beetle species richness across this forest biome, indicating an ongoing process of mammal-dung beetle niche-mediated co-decline. We found a strong relationship between the species composition of both taxa, in which dung beetle species dissimilarity apparently track changes in mammalian dissimilarity, typically in 80% of all cases. Co-variables such as phytomass and climatic variables also influenced mammal-dung beetle patterns of co-decline along the Atlantic Forest. We conclude that dung beetle diversity and community assembly are shaped by the remaining co-occurring mammal assemblages and their functional traits, and both groups were governed by environmental features. We emphasize that ecosystem-wide effects of mammal population declines remain poorly understood both quantitatively and qualitatively, and curbing large vertebrate defaunation will ensure the persistence of co-dependent species.

Wood Pastures: A Transitional Habitat between Forests and Pastures for Dung Beetle Assemblages

“…Only sufficiently diverse assemblages and abundant populations of dung beetles are able to perform their ecological function (acknowledging that body size and functional groups are also important factors [13,14]), but they are declining worldwide. The most serious adverse effects are land use changes, habitat fragmentation [15,16], and declining wild mammal species that provide feces [17,18], all of which transform and intensify traditional animal husbandry [19]. Overgrazing or abandoning pastures leads to a decrease in both abundance and species diversity [20][21][22].…”

El Niño impacts on human‐modified tropical forests: Consequences for dung beetle diversity and associated ecological processes

“…First, lower post-El Niño fruit production can result in large-vertebrate famine Wright, Carrasco, Calderon, & Paton, 1999). These drought and fire-induced changes in vertebrate communities (Barlow, Peres, Henriques, Stouffer, & Wunderle, 2006;Peres, Barlow, & Haugaasen, 2003) are likely to result in cascading effects on dung beetles (Nichols, Gardner, Peres, & Spector, 2009), as co-declines in these two groups have been reported in other human-modified tropical forest landscapes (e.g., Bogoni, Silva, & Peres, 2019;. Second, high rates of tree mortality following droughts and forest fires result in more open canopies, which may affect communities through the hotter and drier forest microclimates (Brando, Oliveria-Santos, Rocha, Cury, & Coe, 2016;Hardwick et al, 2015).…”

Dung beetle‐megafauna trophic networks in Singapore’s fragmented forests

“…However, even generalist dung beetle species have been shown to differentiate variations among differing dung compositions, size, and shape, and display preferences for certain dung types (Peck & Howden, 1984; Nichols & Gardner, 2011; Raine et al, 2019). Moreover, while dung beetle–mammal co‐occurrences have been relatively well studied in the Neotropics (e.g., Bogoni et al, 2014; 2019; Nichols et al, 2016), dung beetle–mammal interactions are little explored in South‐East Asia's forests (Frank et al, 2018; Raine & Slade, 2019). While co‐occurrence data shed light on the possibility of such interactions, these can only be quantified by assessing the specific attractiveness of different dung types to individual species, and building quantitative networks (Frank et al, 2018; Raine & Slade, 2019).…”