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

Abstract

SouthEast Asia's natural habitats are lowland tropical rainforests that harbor a large proportion of the Earth's biodiversity. These rainforests are affected by multiple drivers of biodiversity loss, including deforestation and hunting (Sodhi et al., 2004), with habitat loss being the major driver of species extinctions (Achard et al., 2002). Such large-scale anthropogenic disturbances are driving the extirpation of many large mammals (Bennett, 2000; Sodhi et al., 2004; Steinmetz et al., 2006; Corlett, 2007), resulting in potential cascading effects in tropical rainforest systems, such as secondary extinctions of dependent taxa and the subsequent decline of ecological processes performed by these associated species (Nichols et al., 2009). Scarabaeine dung beetles (Coleoptera: Scarabaeoidea) rely primarily on mammal dung as a food resource for adult beetles and their larvae (Hanski & Cambefort, 1991). Their diversity of dung manipulation, relocation, and consumption contributes to a series of beneficial ecosystem functions and services to tropical rainforests, such as secondary seed dispersal and nutrient cycling (Nichols et al., 2008). Thus, declines in mammal populations, resulting in reduced availability and changing composition of dung resources in tropical rainforests, are predicted to lead to changes in dung beetle communities and cascading effects for ecosystem functioning in these systems (Nichols et al., 2009; Raine & Slade, 2019). Recent work has shown that most dung beetles are generalists when foraging (Frank et al., 2018). 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 SouthEast 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). The first quantitative dung beetle-mammal network for a tropical forest region has recently been built for the Atlantic forest

Biodiversidade e funções ecossistêmicas de coleópteros coprófagos em diferentes usos do solo na microrregião de Ituiutaba (MG)

“…Podendo explorar excrementos dos mais diversos mamíferos, podendo ser considerados oportunistas por não serem especialistas de excrementos de um determinado animal (Hanski & Cambefort, 1991). Análises globais recentes sobre especializações tróficas de escaravelhos mostraram que a maioria das espécies mostra baixa especificidade de recursos e generalismo em toda a comunidade e são generalistas quando forrageiam (Frank et al, 2018, Ong et al, 2020.…”

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

“…For instance, networks using laid out dung were highly generalized (mean ± sd H 2 ′ = 0.23 ± 0.17 in 116 datasets, Frank et al, 2018b ), while our two DNA-based networks showed a much higher level of specialization ( H 2 ′ = 0.41 and 0.49). Partly, this is because the studies included in the Frank et al (2018a) , Frank et al (2018b) meta-analysis and others were often limited by dung access and often used dung from available domestic animals or animals from local zoos rather than naturally occurring dung in a habitat ( Martín-Piera & Lobo, 1996 ; Errouissi et al, 2004 ; Korasaki et al, 2013 ; Frank et al, 2018a ; Raine et al, 2018 ; Ong, Slade & Lim, 2020 ). Experimentally laying out dung could change environmental variables that are important for both attractiveness (dung volume) and natural encounter rates on the landscape (activity windows).…”

“…Dung beetles have been used as indicator species of habitat quality because of their sensitivity to habitat degradation, both in terms of deforestation and defaunation and their ecological importance ( Nichols et al, 2007 ; Korasaki et al, 2013 ; Bicknell et al, 2014 ; Ong, Slade & Lim, 2020 ). The primary source of nutrition for most dung beetles is thought to be moist dung from large mammals ( Hanski & Cambefort, 1991 ; Holter & Scholtz Clarke, 2007 ; Raine et al, 2018 ; Raine & Slade, 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.…”

Dung beetles as vertebrate samplers – a test of high throughput analysis of dung beetle iDNA

“…Such networks have been attempted using traps baited with different mammal dung types (Raine et al . 2019, Ong et al . 2020), but these networks only show indirect interactions through the of attractiveness of dung to the beetles, rather than showing direct feeding interactions.…”