The impact of grazing on dung beetle diversity depends on both biogeographical and ecological context

Abstract

Aim We analysed the effects of grazing on the diversity and structure of dung beetle communities to see whether the biogeographical and ecological contexts influence dung beetle responses. We hypothesized that the responses of dung beetle communities are modulated by both the ecological conditions resulting from the transformation of native vegetation into grazing areas, and the history of the species inhabiting different biogeographical provinces. Location The state of Hidalgo, in the Mexican Transition Zone, central Mexico. Methods We used a standardized hierarchical sampling procedure in three biogeographical provinces located in Hidalgo. Within each province, we identified the dominant vegetation types, and within these we identified the sites with native vegetation and those modified by grazing. The design included 800 baited pitfall traps, and allowed us to study the response of dung beetle communities with different biogeographical histories to ecological context. Results We captured 8707 beetles belonging to 37 species and 17 genera in the subfamily Scarabaeinae. We found that grazing areas only had a negative effect on dung beetle diversity in tropical forest; conversely, in dry environments (pine–oak forest and xerophilous scrubland) diversity in grazing areas was higher than in the native vegetation sites. We did not detect a clear effect in cloud forest sites. Species turnover between the native vegetation and pastures was high locally, and low over larger spatial scales (vegetation type or biogeographical province). In all four vegetation types grazing was associated with differences in dung beetle community composition. Main conclusions The impact of grazing on dung beetle diversity is dependent to a considerable degree on the local ecological conditions and the biogeographical context that has shaped the composition of communities over time.

A dirty job: manure removal by dung beetles in both a cattle ranch and laboratory setting

“…Furthermore, the topography in pastures is plain, with few rocks and big roots, thus allowing beetles to bury dung more rapidly than in forests. This response is similar to that detected in pine-oak forest of the Sierra Madre Oriental, and in xerophilous scrublands of the Mexican Plateau (Verd u et al, 2007;Barrag an et al, 2014). However, the increase in beetle abundance in pastures is a response to current ecological conditions and to the biogeographical history of these mixed temperate forests of central Mexico (Favila, 2012;Barrag an et al, 2014).…”

“…This may contribute to their high abundance, because dung beetles require a proper surface to construct tunnels and chambers for food and nesting. However, the increase in beetle abundance in pastures is a response to current ecological conditions and to the biogeographical history of these mixed temperate forests of central Mexico (Favila, 2012;Barrag an et al, 2014). This response is similar to that detected in pine-oak forest of the Sierra Madre Oriental, and in xerophilous scrublands of the Mexican Plateau (Verd u et al, 2007;Barrag an et al, 2014).…”

“…In pastures, livestock management modifies environmental conditions (e.g., reducing forested areas, impeding natural regeneration, growing non-native pastures, and polluting water and soil), apparently without a drastic effect on the diversity of dung beetle communities inhabiting the highlands in our study area. This work is the first to document dung removal in temperate forests of the MTZ, where dung beetle species with different biogeographic affinities coexist, including species that tolerate habitat modifications related to grazing Verd u et al, 2007;R€ os et al, 2012;Barrag an et al, 2014). The amount of dung removed both in field mesocosms and in the laboratory was positively related to species biomass, with the largest beetles (>110 mg) removing the most dung.…”

“…This work is the first to document dung removal in temperate forests of the MTZ, where dung beetle species with different biogeographic affinities coexist, including species that tolerate habitat modifications related to grazing Verd u et al, 2007;R€ os et al, 2012;Barrag an et al, 2014). Therefore, this ecosystem process may not only depend on species richness as the relationship between biodiversity and ecosystem functioning asserts.…”

“…Traps were plastic containers (19 cm diameter, 9 cm deep) buried flush with the soil, with ethylene glycol inside (30%) to preserve the insects. Traps were left open for 48 h. More details on this sampling method and its efficiency for dung beetle inventories in the region are described in Verd u et al (2007) and Barrag an et al (2014). Species identification was done by comparison with a local reference collection, and with the help of Fernando Escobar (Instituto de Ecolog ıa, A.C., Xalapa, Mexico).…”