The effects of land use change on native dung beetle diversity and function in Australia's Wet Tropics

The impacts of land use change on biodiversity and ecosystem functions are variable, particularly in fragmented tropical rainforest systems with high diversity. Dung beetles (Scarabaeinae) are an ideal group to investigate the relationship between land use change, diversity and ecosystem function as they are easily surveyed, sensitive to habitat modification and perform many ecosystem functions. Although this relationship has been investigated for dung beetles in some tropical regions, there has been no study assessing how native dung beetles in Australia's tropical rainforests respond to deforestation, and what the corresponding consequences are for dung removal (a key ecosystem function fulfilled by dung beetles). In this study we investigated the relationship between dung beetle community attributes (determined through trapping) and function (using dung removal experiments that allowed different dung beetle functional groups to access the dung) in rainforest and cleared pasture in a tropical landscape in Australia's Wet Tropics. Species richness, abundance and biomass were higher in rainforest compared to adjacent pasture, and species composition between these land use types differed significantly. However, average body size and evenness in body size were higher in pasture than in rainforest. Dung removal was higher in rainforest than in pasture when both functional groups or tunnelers only could access the dung. Increased dung removal in the rainforest was explained by higher biodiversity and dominance of a small number of species with distinct body sizes, as dung removal was best predicted by the evenness in body size of the community. Our findings suggest that functional traits (including body size and dung relocation behaviour) present in a dung beetle community are key drivers of dung removal. Overall, our results show that deforestation has reduced native dung beetle diversity in Australian tropical landscapes, which negatively impacts on the capacity for dung removal by dung beetles in this region.     

Nesting strategies affect altitudinal distribution and habitat use in Alpine dung beetle communities

1. Dung beetles are key contributors to a suite of ecosystem services. Understanding the factors that dictate their distributions is a necessary step towards preventing negative impacts of biodiversity loss. 2. Alpine dung beetle communities were analysed along altitudinal gradients to assess how different components of the community, defined in terms of nesting strategy [dung‐ovipositing Aphodiidae (DOAs), soil‐ovipositing Aphodiidae (SOAs) and two paracoprid (PAR) groups, Geotrupidae and Scarabaeidae] and parameters relevant to dung removal rates (species richness, total biomass and functional diversity), are distributed, and to identify to which environmental factors they respond. 3. Species richness declined with altitude. There was no significant variation in functional diversity or total biomass in relation to altitude. There were significant variations when considered by nesting group: DOA species richness and biomass decreased, SOA biomass increased, and Geotrupidae biomass showed a non‐linear trend, as altitude increased. 4. Functional diversity and total species richness were positively related to vegetation cover. DOA species richness was highest in forest and scrub; SOA species richness was highest in grassland and PAR species richness was lowest in rocky areas. 5. Dung beetle species show different trends in species richness and biomass depending on nesting strategy. Management to promote the dung beetle community should include maintenance of a mosaic of habitat types. Given the likely importance of species richness and biomass to ecosystem functioning, and the complimentary effect of different dung beetle groups, such a strategy may protect and enhance the ecosystem services that Alpine dung beetles provide.     

Dung beetle communities as biological indicators of riparian forest widths in southern Brazil

Riparian forests provide important habitat for many wildlife species and are sensitive to landscape change. Among terrestrial invertebrates, dung beetles have been used to investigate the effects of environmental disturbances on forest structure and diversity. Since many studies demonstrated a negative response of dung beetle communities to increasing forest fragmentation, and that most dung beetle species had a more pronounced occurrence during warmest seasons, three hypotheses were tested: (1) Scarabaeinae richness, abundance, diversity and evenness are lower in thinner riparian zone widths than in wider widths during the warmest seasons; (2) Scarabaeinae richness and abundance are positively influenced by leaf litter coverage and height and canopy cover; and (3) Scarabaeinae composition varies with the reduction in riparian vegetation and among annual seasons. We selected four fragments with different riparian zone widths in three secondary streams in southern Brazil. In each fragment, four sampling periods were carried out seasonally between spring 2010 and winter 2011. We collected dung beetles using pitfall traps with two types of bait. We collected 1289 specimens distributed among 29 species. In spring and summer, dung beetle richness was higher in fragments with the widest riparian zone than in those with a thinner riparian zone, and it did not vary between fragments in fall and winter seasons. Dung beetle abundance did not differ among fragments with different riparian zone widths, but it was higher in spring and summer than fall and winter. Richness and abundance were positively influenced by leaf litter. While dung beetle diversity was higher in fragments with wider riparian zone widths than in those with thinner widths, the evenness was similar among fragments. Dung beetle composition differed between the fragments with the widest and thinnest riparian zones, and it also varied among the seasons. Our results suggest that decreased riparian zones affect negatively to dung beetle community structure in southern Brazil. Fragments with thinner riparian zones had lower beetle richness in warmest seasons and an altered community composition. In this sense, the dung beetles are potentially good indicators of riparian forest fragmentation since some species were indicators of a particular riparian zone width. From a conservation perspective, our results demonstrate that the new Brazilian Forest Code will greatly jeopardize not only the terrestrial and aquatic biodiversity of these ecosystems, but also countless other ecological functions.     

Disentangling the ‘brown world’ faecal–detritus interaction web: dung beetle effects on soil microbial properties

Many ecosystem services are sustained by the combined action of microscopic and macroscopic organisms, and shaped by interactions between the two. However, studies tend to focus on only one of these two components. We combined the two by investigating the impact of macrofauna on microbial community composition and functioning in the context of a major ecosystem process: the decomposition of dung. We compared bacterial communities of pasture soil and experimental dung pats inhabited by one (Aphodius), two (Aphodius and Geotrupes), or no dung beetle genera. Overall, we found distinct microbial communities in soil and dung samples, and that the communities converged over the course of the experiment. Characterising the soil microbial communities underlying the dung pats revealed a significant interactive effect between the microflora and macrofauna, where the diversity and composition of microbial communities was significantly affected by the presence or absence of dung beetles. The specific identity of the beetles had no detectable impact, but the microbial evenness was lower in the presence of both Aphodius and Geotrupes than in the presence of Aphodius alone. Differences in microbial community composition were associated with differences in substrate usage as measured by Ecoplates. Moreover, microbial communities with similar compositions showed more similar substrate usage. Our study suggests that the presence of macrofauna (dung beetles) will modify the microflora (bacteria) of both dung pats and pasture soil, including community diversity and functioning. In particular, the presence of dung beetles promotes the transfer of bacteria across the soil–dung interface, resulting in increased similarity in community structure and functioning. The results demonstrate that to understand how microbes contribute to the ecosystem process of dung decomposition, there is a need to understand their interactions with larger co‐occurring fauna.     

The impact of overgrazing on dung beetle diversity in the Italian Maritime Alps

Dung beetles (Coleoptera: Scarabaeidae) are undoubtedly the most typical and ecologically relevant insects of grazed alpine habitats because they provide valuable ecological services such as biological pest control and soil fertilization. Despite the great ecological contribution of these insects to pasture ecosystem functioning, little is known about their direct or indirect relationships with pastoral activities. The main aim of the study was to assess whether dung beetle diversity was influenced by different intensities of cattle grazing. Dung beetle communities of two adjacent alpine valleys within the Maritime Alps Natural Park (north-western Italian Alps), representing overgrazed and ungrazed pastures, were studied by pitfall trapping. A hierarchical design (three levels: valleys, transects, and replicates) was established for additive partitioning of γ-diversity and Indicator Species Analysis. Evenness and Shannon diversity were significantly higher at the ungrazed than at the overgrazed site because abundances were much more evenly distributed at the former than at the latter site (where one species was dominant over all the others). Dung beetle abundance and species richness of the overgrazed graminaceous pasture vegetation types were in most cases significantly lower than those of the ungrazed nongraminaceous vegetation type. In the additive partitioning of γ -diversity analysis relative to the whole study area, the randomization procedure indicated that the contribution of β to γ-diversity was significantly different from that expected by chance, suggesting that one or more environmental factors has intervened to change the partition of total diversity in the system considered. The analysis of the preferences and fidelity of species (Indicator Species Analysis) showed that only one species chose overgrazed pastures; all the others positively selected the ungrazed site, or the only ungrazed pasture vegetation type (Rumicetum alpini Beger) occurring at the overgrazed site. Results conformed to evidences that overgrazing represents a serious threat to the conservation of alpine dung beetles. To conserve local dung beetle assemblages, especially in protected areas, cattle overgrazing should be avoided. This does not mean, however, that pastoral activities are incompatible with biodiversity conservation. The contemporaneous presence of wild ungulates and low intensity extensive pastoral activities may be useful to preserve both local dung beetle assemblages and alpine pasture ecosystems.     

Using dung beetles to evaluate the effects of urbanization on Atlantic Forest biodiversity

We used dung beetles to evaluate the impact of urbanization on insect biodiversity in three Atlantic Forest fragments in Londrina, Paraná, Brazil. This study provides the first empirical evidence of the impact of urbanization on richness, abundance, composition and guild structure of dung beetle communities from the Brazilian Atlantic Forest. We evaluated the community aspects (abundance, richness, composition and food guilds) of dung beetles in fragments with different degrees of immersion in the urban matrix using pitfall traps with four alternative baits (rotten meat, rotten fish, pig dung and decaying banana). A total of 1 719 individuals were collected, belonging to 29 species from 11 genera and six Scarabaeinae tribes. The most urban‐immersed fragment showed a higher species dominance and the beetle community captured on dung presented the greatest evenness. The beetle communities were distinct with respect to the fragments and feeding habits. Except for the dung beetle assemblage in the most urbanized forest fragment, all others exhibited contrasting differences in species composition attracted to each bait type. Our results clearly show that the degree of urbanization affects Atlantic Forest dung beetle communities and that the preservation of forest fragments inside the cities, even small ones, can provide refuges for Scarabaeinae.     

Fire? They don't give a dung! The resilience of dung beetles to fire in a tropical savanna

1. Disturbance is a strong driver of community assembly and fire has long been recognised as one of the main disturbances of terrestrial ecosystems. This study tested the resilience of dung beetles to fire events in campos rupestres, which is a tropical savanna ecosystem that evolved under a frequent fire regime, by assessing the resistance and recovery of their communities. 2. Dung beetles were sampled before and after a fire event and the effect of fire on dung beetle richness, abundance, mean community biomass and composition was tested. The effects of time since last fire and fire frequency on the community were also tested. 3. No effect of fire occurrence, time since last fire and fire frequency on any community variable was found. 4. Some non‐mutually exclusive mechanisms promoting the resistance and recovery of dung beetles in campos rupestres could be acting in synergy. One potential mechanism is the mismatched seasonality between fire events and dung beetle occurrence, as fires occur during the dry season and dung beetles are present above ground during the rainy season. Furthermore, dung beetles are insects that remain buried during most of their lifetime, which could protect individuals from being burned. Another potential mechanism is the replacement of species in burned areas by the movement of individuals from unburned areas, attracted by resources and/or by metacommunity dynamics. 5. It is concluded that in this ‘fire‐dependent’ ecosystem, dung beetle communities are resilient to fire and seem not to be structured by this disturbance.     

Down‐sizing of dung beetle assemblages over the last 53 000 years is consistent with a dominant effect of megafauna losses

The ongoing down‐sizing of the global mammal communities is assumed to have subsequent effects on mutualistic species communities. Dung beetles co‐evolved with large‐sized animals since millennia and depend on the megafauna feces of an appropriate size. Mammal community down‐sizing as a result of past and ongoing megafauna losses is therefore likely to result in a down‐sizing of dung beetle communities. However, empirical evidence for this co‐down‐sizing is lacking especially on larger spatial scales and over extended periods of time. Here, we show a significant down‐sizing of European dung beetle assemblages over the last ~53 000 years by relating Quaternary fossil records with trait information on body size of beetles. This significant down‐sizing of dung beetle communities was thereby not linear, but characterized by a weak decrease until the early Holocene but a strong acceleration in the recent pre‐history, from 6–7000 years BP onwards. This acceleration of down‐sizing coincides with the completion of the Quaternary megafauna extinction and the start of major shifts in human agricultural land‐use. In contrast, assemblage mean body size of non‐coprophagous scarabids as well as ground beetles – two groups of beetles with no or weak relations to megafauna – was observed to increase towards the present with an acceleration of body size increase coinciding with the onset of late‐glacial warming (14 200 years BP). In summary, the observed late‐Quaternary down‐sizing of European dung beetle communities is consistent with an effect of pre‐historic megafauna losses, and not with the coincident general warming. Ongoing down‐sizing of mammal communities is therefore likely to result in further down‐sizing of dung beetle assemblages, with potential effects on their important role for nutrient cycling and secondary seed dispersal in natural and extensive agro‐ecosystems. Future nature management initiatives could halt or even reverse this functional diversity loss via effective protection or restoration of megafauna communities.     

Relationship between land uses and diversity of dung beetles (Coleoptera: Scarabaeinae) in the southern Atlantic forest of Argentina: which are the key factors?

The loss of natural habitats is one of the main drivers of biodiversity decline. Anthropogenic land uses preserving biotic and abiotic conditions of the native ecosystem are more suitable to preserve the native biodiversity. In this study, we explored changes in species richness and composition in different land uses of the southern Atlantic forest, considering three independent factors: (1) canopy (presence–absence), (2) type of vegetation (native–exotic) and (3) livestock (presence–absence). We expected a gradient of response in the richness and composition of the native forest dung beetle community, from land uses preserving canopy and native vegetation to open land uses with exotic vegetation. Dung beetles were sampled in protected native forests and four land uses, using two potential food resources: human dung and carrion. The species richness and composition of each habitat, as well as differences in composition and the influence of factors over diversity, were then analyzed. As expected, our results showed that land uses preserving canopy and native vegetation maintain the dung beetle diversity of the native forest. Moreover, while the three factors analyzed influenced dung beetle diversity, canopy cover was the main driver of dung beetle diversity loss. The main conclusion of this study is that the conservation of canopy (either native or exotic) is determinant to preserve highly diverse dung beetle communities and subsequently, the ecological functions performed by this taxon. However, the ecophysiological mechanism behind the response of dung beetles to habitat disturbance is poorly understood.     

Dung beetles and their ecological functions in three agroforestry systems in the Lacandona rainforest of Mexico

There is growing interest in evaluating the impact that management intensity of agroecosystems has on animal communities and their ecological functions. Dung beetles are a highly used focal taxon for assessing the effects of anthropogenic disturbances and management practices on biodiversity. In the Lacandona rainforest region in southern Mexico, we quantified several metrics of the dung beetle community (number of species, number of individuals, total biomass, mean beetle size) and four of their ecological functions (dung removal, soil excavation, seed dispersal, seed exhumation) in conserved rainforest and three agroforestry systems with different management intensities: rustic cocoa, polyculture cocoa, and rubber monoculture. We also assessed the correlation between dung removal and the other functions, as well as the relationships between functions and community metrics. Land-use type affected the dung beetle communities as well as their functions, with negative effects on response variables in the most intensely managed agroecosystems (polyculture cocoa and rubber). Rustic cocoa had values similar to those of the conserved forest for all functions and community metrics, except the mean number of species per trap. Dung removal was correlated with the other ecological functions. The mean number of species per trap was significantly associated with all four functions. In our study region rustic cocoa plantations favor the maintenance of a high proportion of dung beetle species and maintain their ecological functions. Our findings corroborate that agroecosystems with less intense management may contribute to buffering the effects of landscape homogenization caused by more intensely managed agroecosystems, such as rubber plantations.     

Dung beetle community composition affects dung turnover in subtropical US grasslands

1. An important service in many ecosystems is the turnover and degradation of dung deposited by cattle. Dung beetles are the primary group of insects responsible for dung turnover, and factors affecting their abundance and distribution thus impact dung degradation. Lands lost to grazing due to dung buildup and pasture contamination total millions of acres per year in US pastures.
2. We evaluated the structural differences in dung beetle assemblages in natural grasslands versus a managed agroecosystem in subtropical southeastern Florida (USA). We measured the direct effect of dung longevity when dung beetle fauna normally inhabiting dung pats were excluded.
3. Our results indicate dung beetle abundance, functional diversity, and species richness have a substantial impact on the rate of dung turnover in subtropical pastoral lands with ~70% of dung removed from the soil surface after three months. Functional diversity and evenness did not have a significant positive effect on dung removal in managed, versus natural grasslands demonstrating a strong relationship between dung beetle assemblage composition and delivery of a key ecological process, dung degradation.
4. We suggest the importance of trees, which provide a thermal refuge for beetles, should be dispersed within matrixes of open pasture areas and within proximity to adjacent closed‐canopy hammocks to facilitate the exchange of dung beetles between habitats and therefore maintain the provisioning of dung degradation services by dung beetle assemblages.

     

The Importance of Maize Management on Dung Beetle Communities in Atlantic Forest Fragments

Dung beetle community structures changes due to the effects of destruction, fragmentation, isolation and decrease in tropical forest area, and therefore are considered ecological indicators. In order to assess the influence of type of maize cultivated and associated maize management on dung beetle communities in Atlantic Forest fragments surrounded by conventional and transgenic maize were evaluated 40 Atlantic Forest fragments of different sizes, 20 surrounded by GM maize and 20 surrounded by conventional maize, in February 2013 and 2014 in Southern Brazil. After applying a sampling protocol in each fragment (10 pitfall traps baited with human feces or carrion exposed for 48 h), a total of 3454 individuals from 44 species were captured: 1142 individuals from 38 species in GM maize surrounded fragments, and 2312 from 42 species in conventional maize surrounded fragments. Differences in dung beetle communities were found between GM and conventional maize communities. As expected for fragmented areas, the covariance analysis showed a greater species richness in larger fragments under both conditions; however species richness was greater in fragments surrounded by conventional maize. Dung beetle structure in the forest fragments was explained by environmental variables, fragment area, spatial distance and also type of maize (transgenic or conventional) associated with maize management techniques. In Southern Brazil’s scenario, the use of GM maize combined with associated agricultural management may be accelerating the loss of diversity in Atlantic Forest areas, and consequently, important ecosystem services provided by dung beetles may be lost.     

Linking Biodiversity,the Environment and Ecosystem Functioning: Ecological Functions of Dung Beetles Along a Tropical Elevational Gradient

Biodiversity loss and anthropogenic environmental changes are known to impact ecosystem functions and services. However, there are still some uncertainties such as confounding environmental factors other than community attributes that affect ecosystem functioning. Our goal was to understand what factors influence the performance of Scarabaeinae dung beetle functions, testing the hypothesis that both community attributes and environmental variables influence the performance. Toward this aim, we collected dung beetles along an elevational gradient (800–1400 m a.s.l.) in the Espinhaço mountain range (Brazil) and quantified dung beetle functions, that is, dung removal, soil excavation and secondary seed dispersal. We recorded data on environmental factors related to climate, soil and vegetation and evaluated their effects on dung beetle functions. Dung beetle ecological functions declined with elevation and the decrease was more pronounced than richness, indicating that there are other factors involved in functions performance besides diversity of beetles. Indeed, we found that the ecological functions measured were dependent on both dung beetle community attributes and environmental factors. Climate, soil and vegetation influenced dung beetle function performance as much as richness, abundance and body size. Dung beetle functional diversity did not explain any of the functions measured. Our study demonstrates that ecological functions are directly influenced by both community attributes and environmental variables and confirms the link between biodiversity, environment and ecosystem functioning.     

Cumulative annual dung beetle diversity in Mediterranean seasonal environments

Species diversity assessments should consider the dynamic nature of ecological communities, especially in highly seasonal ecosystems. Here we provide a comprehensive framework for analysing seasonal changes in species composition, richness and diversity in two local dung beetle (Coleoptera: Scarabaeoidea: Aphodiidae, Geotrupidae, and Scarabaeidae) communities from Western Tuscany (Italy), in the Mediterranean ecoregion. We test whether, in this highly seasonal region, cumulative annual diversity is an oversimplification of well differentiated seasonal communities. Data were obtained through repeated standardised samples collected regularly over an entire year. We clearly identify different summer and winter communities at each site based on species composition and abundance. Seasonal richness and diversity values are different from the cumulative annual values, as a consequence of beta diversity between seasons, and some dung beetle species are identified as idiosyncratic of each particular season. Both ecological (niche partitioning) and biogeographical factors are suggested as drivers of these temporal variations. Thus, because local inventories of fauna that include records over long time periods actually reflect situations where coexistence and interactions are unlikely to occur, highly seasonal sites must be viewed as having temporally differentiated communities in order to reach feasible and reliable baselines for local diversity assessments.     

Use of habitat resources by scarab dung beetles in an savanna

In the Queen Elizabeth National Park, Uganda, we compared the scarab beetle assemblages in the dung of three wild ungulates (African buffalo, a ruminant foregut fermenter; hippopotamus, nonruminant foregut fermenter; and warthog, nonruminant hindgut fermenter). Dung was collected from two sandy-clay soils with different percentage of coarse sand. We aimed at investigating habitat resource selection by dung beetle species within a savanna natural contest with abundant and diverse food availability. Analyses were performed to detect differences for dung beetle assemblages in abundance, diversity, functional groups. Species richness in the three dung types and in the two soil types was similar. However, warthog dung and sandy-rich soil appeared the preferred habitat resources, in terms of abundance and biomass, while hippopotamus dung hosted the lowest values for these parameters. The analysis of functional groups revealed that slow-burying tunnellers held the major role, both in terms of abundance and biomass, and were mainly found in warthog dung.     

Patterns of alimentary resource use by dung beetles in introduced Brazilian pastures: Cattle versus sheep dung

Dung beetles (Coleoptera: Scarabaeidae) perform essential ecological functions in pastures, such as dung removal, nutrient recycling and parasite control. However, the patterns of alimentary use by dung beetles in introduced Brazilian pastures are poorly known. Here, we compared dung beetle species richness, abundance and species composition in cattle and sheep dung, and identified the dung beetle species preference by each dung type. In January 2019, dung beetles were sampled with pitfall traps baited with cattle and sheep dung in 12 introduced pastures (Urochloa spp.), in Aquidauana, Mato Grosso do Sul, Brazil. A total of 592 individuals belonging to 14 species of dung beetles were collected. Of the 14 species sampled, nine were recorded in both dung types, five were found exclusively in sheep dung and no species was exclusive to cattle dung. Species richness and abundance were higher in sheep dung. Species composition was different between the dung types. Dichotomius bos (Blanchard), Genieridium bidens (Balthasar), Onthophagus aeneus Blanchard and Trichillum externepunctatum Preudhomme de Borre were associated with sheep dung. Our results provide evidence that sheep dung is more attractive to dung beetles with a distinct community species between the two dung types, although the studied pastures have never been used before for sheep breeding. Thus, our data shows that the introduction of a new alimentary resource (e.g. sheep dung) can be an important strategy to help to obtain a more diverse dung beetle assemblage in introduced Brazilian pastures.     

Edge and land use effects on dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) in Brazilian cerrado vegetation

The Edge Influence is one of the most pervasive effects of habitat fragmentation, as many forest remnants in anthropogenic landscapes are within 100 m of edges. Forest remnants may also affect the surrounding anthropogenic matrix, possibly resulting in a matrix–edge–remnant diversity gradient for some species groups. We sampled dung beetles in 15 agricultural landscapes using pitfall traps placed along transects in matrix–edge–remnant gradients. The remnants were a native savanna-like vegetation, the cerrado, and the matrix was composed of three human-dominated environments (sugarcane, eucalyptus, pasture). More species were observed in cerrado remnants than in adjacent land uses. Dung beetles were also more abundant in the cerrado than in the landscape matrix of sugarcane and eucalypt, but not of pasture. Dung beetles were severely affected by anthropogenic land uses, and notwithstanding their high abundance in some land uses such as pasture, the species richness in these areas tended to be smaller than in the cerrado remnants. We also found that the influence of the edge was evident only for abundance, particularly in landscapes with a pasture matrix. However, this land use disrupts the species composition of communities, indicating that communities located in cerrado and pasture have a distinct species composition, and that both communities are affected by edge distance. Thus, anthropogenic land uses may severely affect dung beetles, and this impact can extend to communities located in cerrado remnants as well as to those in matrices, with possible consequences for ecological processes such as decomposition and nutrient cycling.     

Intermediate disturbance promotes diversity and the conservation of dung beetles (Scarabaeoidea: Scarabaeidae and Aphodiidae) in the Eastern Cape,South Africa

Environmental fluctuations, such as changes in climate, agricultural management and anthropogenic land-use patterns can affect the diversity of organisms inhabiting an area. Losses of biodiversity alter ecosystems processes, eroding their capacity to deliver ecosystem services. Dung beetles are critical ecosystem service providers, making them an ideal ecological indicator to explore the effects of land-use change on biodiversity. Dung beetles were sampled across three land-use types, in the summers of 2015 and 2016 in the Eastern Cape province, South Africa. Game ranching is regarded as a relatively low-intensity land use type. It was compared with cattle ranching (medium intensity) and dairy farming (high intensity) to examine their effect on dung beetle assemblage metrics (abundance, species richness and true Shannon diversity index), guild diversity (as nesting guilds) and spatial turnover. The intermediate grazing intensity of cattle ranching supported a higher abundance and diversity of both whole dung beetle assemblage and the nesting guilds, followed by the game ranches and then dairy farms. Differences between the sampling years were dependent on the beetle nesting guild, and largely correlated with rainfall and temperature. Cattle and game ranches shared a higher number of species than either shared with dairy farms. Whittaker's Beta-diversity index showed the highest species turnover between game ranches and dairy farms. A mix of game and cattle ranching, minimising dairy farming or restricting it to already ecological degraded sites, appears the best alternative for maintenance of dung beetle diversity and their ecosystem services. The year-to-year trends of the data were in general consistent, confirming that dung beetles are reliable ecological indicators; but also suggest that climate change that affects rainfall will result in the reduction of the abundance and diversity of this key ecological group.     

Effects of the progressive abandonment of grazing on dung beetle biodiversity: body size matters

Dung beetles are an ecologically important group of insect species inhabiting semi-natural grasslands in Europe. Despite their ecological importance, several dung beetle species are currently facing local threats mainly stemming from changes in land use practices, including the abandonment of pasturelands. The aim of this study was to analyze the impact of the progressive abandonment of grazing lands on dung beetle alpha diversity, abundance, biomass and body size classes. Areas representing a range of trophic resource availability were compared: (i) abandoned, (ii) low and (iii) moderate grazing intensity. A total of 136,884 specimens belonging to 56 species (3 Geotrupinae; 16 Scarabaeinae; 37 Aphodiinae) of dung beetle were collected. Pastureland abandonment was shown to lead to a decrease in alpha diversity and biomass density, a reduction of 22 and 78% respectively in abandoned areas. From a biomass standpoint, the effects of pastureland abandonment varied according to the body size classes of the dung beetles, with larger species proving more susceptible to local extinction. Such body-size dependent variations led us to propose the use of both biomass and abundance data in making assessments since they are differentially sensitive to trophic resource availability. Hence, from a conservationist standpoint, the obtained results suggest that traditional pastureland management with low-moderate grazing intensity should be maintained.