Co-declining mammals and dung beetles: an impending ecological cascade

One elephant may sustain 2 million dung beetles in East African savannason any given day

In East African savannas, in the rainy season, an elephant dung bolus is usually transformed into a flat mat of dung residue within a few hours. We extracted the coprophilous beetles of a dung mat from a 1 kg bolus after a one-night exposure and counted 13,699 specimens, most of them aphodiine dung beetles. This is the largest number of dung beetles per kilogram of mammal dung ever counted. Given that an elephant produces an average of 160 kg of feces per day, we extrapolate that one adult elephant provides food for 2.12 million dung beetles on any given day. The elephant population in the Laikipia-Samburu ecosystem in central Kenya, an elephant-rich environment, can sustain, by sheer extrapolation, 14.3 billion dung beetles in an area of 55,000 km2, which translates to ca. 260,000 dung beetles/km2. The decline or extinction of elephants, at least in East African grasslands, may have a massive cascade effect on the populations of coprophagous beetles and the biota dependent on or gaining an advantage from them.

Ecological indication metrics on dung beetles metacommunities in native forests and Pinus monocultures

Beetles of the subfamily Scarabaeinae are commonly used as ecological indicators in studies about the effects of environmental changes. We analyzed the influence of the type of habitat, vegetation, mammals (as food resource), and temperature on dung beetle metacommunities in subtropical native forests and Pinus monocultures to evaluate the factors driving these assemblages. In the summer of 2018/2019, we sampled 12 areas in Southern Brazil, six Pinus monocultures and six native forests. We performed a dispersal test, applying a marking-recapture method. Some recaptures occurred in different habitats, showing low dispersal between habitats. We recorded behavioral activities confirming the use of both native forest and Pinus areas. The metrics did not reflect the difference in the environmental quality of the areas regarding species richness and diversity in different habitats. This shows that these metrics are not the best when using dung beetle assemblages as ecological indicators of biodiversity loss resulting from land-use changes, requiring complementing the analysis with composition analysis methods. When we partitioned beta diversity between habitats, we observed a dissimilarity between Pinus monocultures and native forest assemblages due to species substitution, with many species contributing to the dissimilarity between habitats. In our structural equation models, the influence of environmental factors on metacommunities showed no predictor related to dung beetle richness, but several variables influenced their abundance.

Human Disturbance Affects Dung Beetle Assemblages in French Guiana Forests

French Guiana forests are threatened by increasing human activity such as infrastructure development, facilitating access to the forest and, therefore, logging, mining, farming and hunting. To highlight the impact of human pressure on the forest fauna, dung beetle assemblage was analyzed near Saint-Georges-de-l’Oyapock and compared with other sites in French Guiana, considering the distance to the main city and forest cover loss as proxies of human activities. Hill numbers and beta diversity were calculated. Non-metric multidimensional scaling and redundancy analyses were carried out to disentangle the effect of the distance to the nearest city and forest cover loss as proxies of human pressure, but also temperature and rainfall as proxies of climatic variations on dung beetle assemblage. Species richness increased significantly with the distance to the nearest city and decreasing forest cover loss. Assemblage structure varied among sites mainly with distance to the nearest city but also with rainfall. It varied also with forest cover loss, but not significantly. This study showed that human disturbances and climatic conditions, even if represented by proxies, affected dung beetle assemblage structures in French Guiana forests.

Good news! Sampling intensity needed for accurate assessments of dung beetle diversity may be lower in the Neotropics

Ecological studies with Scarabaeinae dung beetles have increased exponentially over the past 30 years, using lethal pitfall traps baited with mammal feces or carrion as the preferred sampling method. Different studies have determined the distance between pitfall traps for effective sampling, but the number of traps is often subjective, leading to excessive or poor sampling. This study provides quantitative guidelines for establishing the sample size for optimal completeness of dung beetle diversity by systematically reviewing the relationship between sampling intensity and sampling coverage, habitat type, and the journal impact factor in peer-reviewed research. We gathered 94 studies covering a range from México to Argentina. Sampling was conducted mainly in forested habitats, followed by treeless agriculture and agroforestry systems, with a median value of 50 pitfall traps per sampled habitat. Sampling completeness was above 0.9 in 95% of the studies. Oversampling ranged from 1 to more than 96,000 individuals, and sampling deficit varied between 2 and 3,300 specimens. Sampling intensity and the journal impact factor were significantly and positively correlated with oversampling, but these variables did not explain the sampling deficit. The positive correlation between journal impact factor and oversampling may reflect a publication bias where high-impact journals and researchers seek more generalizable information obtained with a higher sampling intensity. Dung beetle oversampling was not homogeneous between habitats, being highest in old-growth forests and lowest in disturbed habitats such as pastures and forest edges. Our results show that the collection intensity used in dung beetle studies should be reconsidered carefully. By incorporating ethical principles used in animal science, we suggest sampling guidelines for a robust sampling scheme of dung beetle diversity, which would also prevent oversampling. Consciously reducing sampling intensity will make resource use more cost-effective. We suggest increasing the number of independent sampling units rather than intensifying subsampling, thereby increasing the predictive power of statistical models to obtain more robust evidence of the phenomena under study.

Replacing low-intensity cattle pasture with oil palm conserves dung beetle functional diversity when paired with forest protection

Meeting rising demand for oil palm whilst minimizing the loss of tropical biodiversity and associated ecosystem functions is a core conservation challenge. One potential solution is focusing the expansion of high-yielding crops on presently low-yielding farmlands alongside protecting nearby tropical forests that can enhance provision of ecosystem functions. A key question is how this solution would impact invertebrate functional diversity. We focus on oil palm in the Colombian Llanos, where plantations are replacing improved cattle pastures and forest fragments, and on dung beetles, which play key functional roles in nutrient cycling and secondary seed dispersal. We show that functional richness and functional diversity of dung beetles is greater in oil palm than in cattle pasture, and that functional metrics did not differ between oil palm and remnant forest. The abundance-size class profile of dung beetles in oil palm was more similar to forest than to pasture, which had lower abundances of the smallest and largest dung beetles. The abundance of tunneling and rolling dung beetles did not differ between oil palm and forest, while higher forest cover increased the abundance of diurnal and generalist-feeding beetles in oil palm landscapes. This suggests that prioritizing agricultural development on low-yielding cattle pasture will have positive effects on functional diversity and highlights the need for forest protection to maintain ecosystem functioning within agricultural landscapes.

Abundance and Diversity of Dung Beetles (Coleoptera: Scarabaeoidea) as Affected by Grazing Management in the Nebraska Sandhills Ecosystem

Dung beetles (Coleoptera: Scarabaeoidea) serve a significant role in regulating ecosystem services on rangelands. However, the influence of grazing management on dung beetle communities remains largely unknown. The purpose of this study was to investigate dung beetle abundance and diversity throughout the grazing season in the Nebraska Sandhills Ecoregion. Grazing treatments included: continuous grazing (CONT), low-stocking rotational grazing (LSR), high-stocking rotational grazing (HSR), and no grazing (NG). The abundance and diversity of dung beetles were measured in the 2014 and 2015 grazing seasons using dung-baited pitfall traps. Dung beetle abundance for each grazing treatment was characterized through four indices: peak abundance, species richness, Simpson's diversity index, and Simpson's evenness. A total of 4,192 dung beetles were collected through both years of trapping in this study. Peak abundance and species richness were greater in grazed treatments when compared to NG in both years. Peak abundance in the HSR was 200% (2014) and 120% (2015) higher than in the LSR. Species richness in the HSR was 70% (2014) and 61% (2015) higher than in the LSR, and 89% (2014) and 133% (2015) higher than in CONT. Simpson's diversity index was lower in the NG and CONT treatments when compared to the LSR or HSR treatments for both years. We conclude that rotational grazing, regardless of stocking density, promoted dung beetle abundance and diversity within the Nebraska Sandhills Ecoregion.

A decrease in taxonomic and functional diversity of dung beetles impacts the ecosystem function of manure removal in altered subtropical habitats

The loss of biodiversity-caused mainly by habitat destruction-is one of the environmental problems with major repercussions on ecosystem functioning. Nevertheless, our understanding of the functional consequences of habitat changes on the communities and ecosystems remains limited to a small number of case studies. We evaluated the change in taxonomic and functional diversity of copro-necrophagous beetles (Scarabaeinae) and their relationship with the varying environmental factors present in four habitats with different degrees of disturbance. Furthermore, we evaluated how changes in taxonomic and functional diversity affect the rates of excrement removal. The collections were carried out at four locations in the state of Santa Catarina, Southern Brazil, on natural systems with different degrees of disturbances (forests in advanced and initial succession) and agroecosystems (silviculture and pastures dedicated to livestock). We collected a total of 1266 dung beetles distributed in 35 species and classified into 11 functional groups. The taxonomic and functional diversity analyses showed that habitats that still maintain an arboreal stratum do not present differences between them, in contrast to habitats dedicated to livestock where there was a significant loss of species and functional groups. The distance between the trees, as well as the air and soil temperatures were determining factors in the selection of species and functional groups. Some of these environmental factors explain the differences in functional traits, represented as varying abundances of the species found. The rates of manure removal from the ecosystem were positively correlated to taxonomic and functional richness as well as biomass of beetles. Thus, we can conclude that habitats with tree strata have the capacity to preserve a larger proportion of the regional set of species as well as the important ones, while preserving the taxonomic and functional diversity and the ecosystem functions, such as the excrement removal rate.

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

Wood pastures are home to a variety of species, including the dung beetle. Dung beetles are an important functional group in decomposition. Specifically, in terms of livestock manure, they not only contribute to nutrient cycling but are key players in supporting human and animal health. Dung beetles, however, are declining in population, and urgent recommendations are needed to reverse this trend. Recommendations need to be based on solid evidence and specific habitats. Herein, we aimed to investigate the role of an intermediate habitat type between forests and pastures. Wood pastures are key areas for dung beetle conservation. For this reason, we compared dung beetle assemblages among forests, wood pastures, and grasslands. We complemented this with studies on the effects of dung type and season at three Hungarian locations. Pitfall traps baited with cattle, sheep, or horse dung were used in forests, wood pastures, and pasture habitats in spring, summer, and autumn. Dung beetle assemblages of wood pastures showed transient characteristics between forests and pastures regarding their abundance, species richness, Shannon diversity, assemblage composition, and indicator species. We identified a strong effect of season and a weak of dung type. Assemblage composition proved to be the most sensitive measure of differences among habitats. The conservation of dung beetles, and the decomposition services they provide, need continuous livestock grazing to provide fresh dung, as well as the maintenance of wood pastures where dung beetle assemblages typical of forests and pastures can both survive.

Environmental DNA metabarcoding of cow dung reveals taxonomic and functional diversity of invertebrate assemblages

Insects and other terrestrial invertebrates are declining in species richness and abundance. This includes the invertebrates associated with herbivore dung, which have been negatively affected by grazing abandonment and the progressive loss of large herbivores since the Late Pleistocene. Importantly, traditional monitoring of these invertebrates is time‐consuming and requires considerable taxonomic expertise, which is becoming increasingly scarce. In this study, we investigated the potential of environmental DNA (eDNA) metabarcoding of cow dung samples for biomonitoring of dung‐associated invertebrates. From eight cowpats we recovered eDNA from 12 orders, 29 families, and at least 54 species of invertebrates (mostly insects), representing several functional groups. Furthermore, species compositions differed between the three sampled habitats of dry grassland, meadow, and forest. These differences were in accordance with the species’ ecology; for instance, several species known to be associated with humid conditions or lower temperatures were found only in the forest habitat. We discuss potential caveats of the method, as well as directions for future study and perspectives for implementation in research and monitoring.

Mechanisms of diversity maintenance in dung beetle assemblages in a heterogeneous tropical landscape

Background

Anthropized landscapes play a crucial role in biodiversity conservation, as they encompass about 90% of the remaining tropical forest. Effective conservation strategies require a deep understanding of how anthropic disturbances determine diversity patterns across these landscapes. Here, we evaluated how attributes and assembly mechanisms of dung beetle communities vary across the Selva El Ocote Biosphere Reserve (REBISO) landscape.

Methods

Community attributes (species diversity, abundance, and biomass) were assessed at the landscape scale, using spatial windows and vegetation classes. Windows were categorized as intact, variegated, or fragmented based on their percent cover of tropical forest. The vegetation classes analyzed were tropical forest, second-growth forest, and pastures.

Results

We collected 15,457 individuals and 55 species. Variegated windows, tropical forests, and second-growth forests showed the highest diversity values, while the lowest values were found in intact windows and pastures. Landscape fragmentation was positively and strongly related to dung beetle diversity and negatively related to their abundance; biomass was positively associated with forest cover. Beta diversity was the primary driver of the high dung beetle diversity in the landscape analyzed.

Discussion

The landscape heterogeneity and its biodiversity-friendly matrix facilitate the complementarity of dung beetle assemblages in the Selva El Ocote Biosphere Reserve. Random processes govern beta diversity patterns in intact and variegated windows. Therefore, vegetation cover in the region is sufficient to maintain a continuous flow of dung beetles between forested landscape segments. However, intense anthropic disturbances acted as deterministic environmental filters in fragmented windows and pastures sites, leading to biotic homogenization processes. Our results suggest that increasing habitat variegation in highly fragmented sites is an effective strategy to prevent or buffer homogenization processes in the REBISO landscape.

Current status of dung beetles (Coleoptera, Scarabaeidae, Scarabaeinae) diversity and conservation in Natural Protected Areas in Chiapas (Mexico)

Natural Protected Areas (NPAs) are consider adequate tools for biodiversity conservation. Currently in Mexico there are 182 federal NPAs classified according to their management objectives. Chiapas is the Mexican state with the highest number of decreed NPAs and also allocates one of the largest territorial extensions for its protection. Unlike other taxa, and despite their proven ability to respond to ecosystem changes, the study of dung beetles within Mexican NPAs has been underestimated, as they are not considered as a priority group within their management and conservation programs. Based on the review of information available in publications and database on dung beetles, a list of 112 species and seven subspecies recorded in 16 of the 19 federal NPAs established in Chiapas is presented. The species recorded by each NPA show a significant correlation with the number of publications, but a low percentage of them correspond to studies with systematic samplings and most of the species reported in several of the NPAs come from sporadic records, which prevents the study of several basic and applied aspects of dung beetles in the region. Therefore, studies that extensively analyze the communities of arthropod groups, such as the Scarabaeinae, are necessary to understand their response to changes in the ecosystem at local and regional scale. It is advisable that these insects be included in the previous justifying studies for the designation or establishment of NPAs and, in turn, considered in the biological monitoring programs of these areas for their capacity as a bioindicator group.

Can taxonomic and functional metrics explain variation in the ecological uniqueness of ecologically-associated animal groups in a modified rainforest?

The conservation of biodiversity requires adequate information about species and ecosystem attributes. The local contribution to β-diversity (LCBD) is a community composition-based metric of ecological uniqueness of sites. Here, we tested the capability of taxonomic and functional attributes of biological communities to explain variation in LCBD at a large spatial extent. We approached this idea using data on dung beetles and mammals (medium-to-large, small and volant) recorded across the Atlantic Forest of South America due to their millennial-scale evolutionary relationship (food providers and consumers). We related LCBD values to both taxonomic and functional metrics via beta regression. Our results revealed that taxonomic and functional features of assemblages can be used to predict variation in ecological uniqueness (LCBD). High LCBD values were associated with low species and functional richness for all animal groups. For dung beetles, high LCBD values were associated with low values of all functional metrics. For mammalian groups high ecological uniqueness was associated with low abundance, low Rao's quadratic entropy, as well as high functional divergence, functional evenness, functional originality, and either low or high functional specialization. This implies that variation in ecological uniqueness can be explained by functional features at large spatial extents, although the type of functional metrics' response of assemblages may be animal group specific. The potential of the LCBD metric to inform about both taxonomic and functional changes at large scales makes its use in conservation planning a highly promising approach.

Trait responses of Peninsular Malaysian dung beetles (Scarabaeidae: Scarabaeinae) to the loss of megafauna dung

The extinction of megafauna may lead to the trophic collapse of ecosystems that depend on the dung that they produce. Some dung beetle species may undergo phenotypic changes in response to altered resource availability. The pronotal width of dung beetles is a trait that can be used as a proxy measure for the amount of dung provisioned during the larval stage. In this study conducted in Peninsular Malaysia, we compare the intraspecific difference in pronotal widths of dung beetles in forests with and without megafauna. Beetles were collected using burrowing interception traps baited with elephant dung. Six species with a minimum sample size of 55 beetles per species were used. Pronotum widths were compared using Bayesian estimation (BEST). There was no credible difference between intraspecific pronotal widths of four species, but credible differences between the mean parameters of two species, Liatongus femoratus and Oniticellus tessellatus. Both these species belong to genera that have a close association with megafauna, while the other are believed to be generalists. This may indicate that species that depend on megafauna dung as a breeding resource undergo a phenotypic change following the loss of their preferred dung type. Phenotypic changes appear to be a pathway which allows species to survive the initial trophic collapse of an ecosystem.

Dung beetle-mammal associations: methods, research trends and future directions

Dung beetles are increasingly used as a study taxon—both as bioindicators of environmental change, and as a model system for exploring ecosystem functioning. The advantages of this focal taxon approach are many; dung beetles are abundant in a wide range of terrestrial ecosystems, speciose, straightforward to sample, respond to environmental gradients and can be easily manipulated to explore species-functioning relationships. However, there remain large gaps in our understanding of the relationship between dung beetles and the mammals they rely on for dung. Here we review the literature, showing that despite an increase in the study of dung beetles linked to ecosystem functioning and to habitat and land use change, there has been little research into their associations with mammals. We summarize the methods and findings from dung beetle–mammal association studies to date, revealing that although empirical field studies of dung beetles rarely include mammal data, those that do, indicate mammal species presence and composition has a large impact on dung beetle species richness and abundance. We then review the methods used to carry out diet preference and ecosystem functioning studies, finding that despite the assumption that dung beetles are generalist feeders, there are few quantitative studies that directly address this. Together this suggests that conclusions about the effects of habitat change on dung beetles are based on incomplete knowledge. We provide recommendations for future work to identify the importance of considering mammal data for dung beetle distributions, composition and their contributions to ecosystem functioning; a critical step if dung beetles are to be used as a reliable bioindicator taxon.

The importance of ecological memory for trophic rewilding as an ecosystem restoration approach

Increasing human pressure on strongly defaunated ecosystems is characteristic of the Anthropocene and calls for proactive restoration approaches that promote self-sustaining, functioning ecosystems. However, the suitability of novel restoration concepts such as trophic rewilding is still under discussion given fragmentary empirical data and limited theory development. Here, we develop a theoretical framework that integrates the concept of 'ecological memory' into trophic rewilding. The ecological memory of an ecosystem is defined as an ecosystem's accumulated abiotic and biotic material and information legacies from past dynamics. By summarising existing knowledge about the ecological effects of megafauna extinction and rewilding across a large range of spatial and temporal scales, we identify two key drivers of ecosystem responses to trophic rewilding: (i) impact potential of (re)introduced megafauna, and (ii) ecological memory characterising the focal ecosystem. The impact potential of (re)introduced megafauna species can be estimated from species properties such as lifetime per capita engineering capacity, population density, home range size and niche overlap with resident species. The importance of ecological memory characterising the focal ecosystem depends on (i) the absolute time since megafauna loss, (ii) the speed of abiotic and biotic turnover, (iii) the strength of species interactions characterising the focal ecosystem, and (iv) the compensatory capacity of surrounding source ecosystems. These properties related to the focal and surrounding ecosystems mediate material and information legacies (its ecological memory) and modulate the net ecosystem impact of (re)introduced megafauna species. We provide practical advice about how to quantify all these properties while highlighting the strong link between ecological memory and historically contingent ecosystem trajectories. With this newly established ecological memory-rewilding framework, we hope to guide future empirical studies that investigate the ecological effects of trophic rewilding and other ecosystem-restoration approaches. The proposed integrated conceptual framework should also assist managers and decision makers to anticipate the possible trajectories of ecosystem dynamics after restoration actions and to weigh plausible alternatives. This will help practitioners to develop adaptive management strategies for trophic rewilding that could facilitate sustainable management of functioning ecosystems in an increasingly human-dominated world.

Microclimatic Conditions for Dung Beetle (Coleoptera: Scarabaeidae) Occurrence: Land Use System as a Determining Factor

Tropical forests account for 7% of the earth's surface harboring more than 50% of the biodiversity on Earth. Unfortunately, deforestation continues at high rates with negative consequences for biodiversity. With the decrease of natural habitats, biodiversity maintenance in areas degraded by human activity is a challenge. In order to maintain biodiversity, both in natural areas and in agro-ecosystems, knowledge of the structure and function of organism communities is important. Dung beetles (Scarabaeidae) play an important role in tropical ecosystems by recycling organic matter. Dung beetle diversity was appraised during 1 yr in an Atlantic forest remnant and five anthropic adjacent vegetation systems. In total, 1,047 individuals were sampled representing 17 species. Scybalocanthon nigriceps was the most abundant (523 individuals: 50%) almost exclusively in forest areas. Ataenius aff. platensis (48 individuals: 4.6%), and Canthon aff. luctuosus (109 individuals: 10.4%) were observed in all areas, while Canthon virens chalybaeus (111 individuals: 10.6%) was limited to anthropic areas. Dung beetle diversity was affected by microclimatic conditions concerning precipitation and air temperature. The greatest abundance and richness was found in the rainy season with a striking reduction in the dry period. The pasture sustained the lowest species diversity and abundance. However, there are clear signs that tree structure and microclimatic conditions similar to forests, as found in agroforestry, can help preserve biodiversity by creating a propitious habitat for native species. This is especially important in the forest regions of the Neotropics where dung beetles exhibit their greatest diversity. As dung beetles greatly depend on mammal feces and carrion, it is suggested that future studies incorporate the occurrence of mammals in investigations of the effects of landscape structure on scarab diversity.

Evidence of forest restoration success and the conservation value of community-owned forests in Southwest China using dung beetles as indicators

Protection of the world’s remaining forests and biodiversity is a matter of global concern. Yunnan, China is home to China’s only mainland tropical rainforests, and 20% of China’s total biodiversity. Despite restoration measures and establishment of new protected areas, this region is still experiencing biodiversity loss due to inadequate management and monitoring. We evaluate restoration success of China’s tropical forests in Xishuangbanna National Nature Reserve (XSBN-NNR), Yunnan, China using dung beetles as an indicator taxon. We sampled across a land-use gradient of human alteration: protected forest, restored forest, community owned forest, and rubber plantation. We collected 3,748 dung beetles from 21 species over a 3 month period. Multivariate analyses revealed unique assemblages in each land-use category, but with restored forest most similar to protected areas, suggesting restoration success in this region. Community forests were more diverse than plantations, suggesting that community forests may be a valuable and practical conservation tool in this region. Most species were generalists, although some had dietary and habitat preferences. Furthermore, dietary niche breadths were, on average, higher in disturbed areas, suggesting that disturbance may result in dietary changes. We show that restoration of tropical forests appears to be successful for a key ecological and biological indicator group- dung beetles. Furthermore, community-owned forests appear to be valuable and practical method of maintaining ecosystem health and biodiversity in the region. Future management in this region would likely benefit from encouragement to maintain community-owned forests, economic incentives for restoring farmland to forest, and increased environmental monitoring across the land-use gradient.

Soil biological responses to, and feedbacks on, trophic rewilding

Trophic rewilding-the (re)introduction of missing large herbivores and/or their predators-is increasingly proposed to restore biodiversity and biotic interactions, but its effects on soils have been largely neglected. The high diversity of soil organisms and the ecological functions they perform mean that the full impact of rewilding on ecosystems cannot be assessed considering only above-ground food webs. Here we outline current understanding on how animal species of rewilding interest affect soil structure, processes and communities, and how in turn soil biota may affect species above ground. We highlight considerable uncertainty in soil responses to and feedbacks on above-ground consumers, with potentially large implications for rewilding interactions with global change. For example, the impact of large herbivores on soil decomposers and plant-soil interactions could lead to reduced carbon sequestration, whereas herbivore interactions with keystone biota such as mycorrhizal fungi, dung beetles and bioturbators could promote native plants and ecosystem heterogeneity. Moreover, (re)inoculation of keystone soil biota could be considered as a strategy to meet some of the objectives of trophic rewilding. Overall, we call for the rewilding research community to engage more with soil ecology experts and consider above-ground-below-ground linkages as integral to assess potential benefits as well as pitfalls.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.

Elevational and Possible Bushmeat Exploitation Effects on Dung Beetle (Scarabaeidae: Scarabaeinae) Communities on Mount Cameroon, West Central Africa

Dung beetle species richness and abundance on Mt Cameroon were investigated to evaluate the effects of elevation. Surveys were done at five different elevations on the southwest facing slope from 216 to 2,102 m above sea level near the tree line at intervals of ~500 m. In total, 27 species and 1,886 specimens were collected during the study. No linear relationship between either species richness or beetle abundance and elevation was found with an expected highest diversity and abundance at low elevation and the lowest diversity and abundance at high elevation. Instead, both the highest diversity and abundance were discovered at the middle elevation (914-1,012 m) with 22 species and 48% of the total catch. The highest diversity indices (Shannon and Simpson) were found at the second lowest elevation (522-625 m). The lowest diversity found at the highest elevation (1,974-2,101 m) included only two species and represented only 4% of the beetles sampled. Unexpected low diversity and abundance at the lowest elevation are hypothesized to be due at least in part to the effects of bushmeat hunting in the more accessible lower elevations and the concomitant effects on dung beetles that mainly utilize mammal dung. The most similar faunas based on Morisita-Horn paired comparisons were those at the two highest and the two lowest elevations while the most dissimilar were the middle compared with the highest elevation. Faunas appear to be divided into high and low elevation communities with a boundary or division at c.1,500-1,750 m elevation.

Spatial and temporal variations of aridity shape dung beetle assemblages towards the Sahara desert

Background

Assemblage responses to environmental gradients are key to understand the general principles behind the assembly and functioning of communities. The spatially and temporally uneven distribution of water availability in drylands creates strong aridity gradients. While the effects of spatial variations of aridity are relatively well known, the influence of the highly-unpredictable seasonal and inter-annual precipitations on dryland communities has been seldom addressed.

Aims

Here, we study the seasonal and inter-annual responses of dung beetle (Coleoptera, Scarabaeidae) communities to the variations of water availability along a semiarid region of the Mediterranean.

Methods

We surveyed a 400 km linear transect along a strong aridity gradient from the Mediterranean coast to the Sahara (Eastern Morocco), during four sampling campaigns: two in the wet season and two in the dry season. We measured species richness, abundance and evenness. Variations in community composition between sites, seasons and years were assessed through beta diversity partitioning of dissimiliarity metrics based on species occurrences and abundances. The effects of climate, soil, vegetation and dung availability were evaluated using Spearman-rank correlations, general linear regressions and partial least-squares generalized linear regressions for community structure, and non-metric multi-dimensional scaling, Permutational Analysis of Variance (PERMANOVA) and distance-based RDA variation partitioning for compositional variations.

Results

Dung beetle abundance and species richness showed large seasonal variations, but remained relatively similar between years. Indeed, aridity and its interaction with season and year were the strongest correlates of variations in species richness and composition. Increasing aridity resulted in decreasing species richness and an ordered replacement of species, namely the substitution of the Mediterranean fauna by desert assemblages dominated by saprophagous and generalist species both in space towards the Sahara and in the dry season.

Discussion

Our study shows that aridity determines composition in dung beetle communities, filtering species both in space and time. Besides the expected decrease in species richness, such environmental filtering promotes a shift towards generalist and saprophagous species in arid conditions, probably related to changes in resource quality along the transect and through the year. Our results highlight the importance of considering the effects of the highly-unpredictable seasonal and inter-annual variations in precipitation when studying dryland communities.

Biodiversity thresholds in invertebrate communities: The responses of dung beetle subgroups to forest loss

Extinction thresholds have been predicted to be critical values of habitat loss in which an abrupt reduction in populations occurs through the interaction between reduced habitat and increased isolation in the landscape. In communities, extinction thresholds are referred to as ‘biodiversity thresholds’. The biodiversity threshold values documented so far occur between 30% and 50% of habitat cover in landscapes. However, the assessment of biodiversity thresholds has mainly focused on vertebrate and plant communities. Here, we evaluated the occurrence of biodiversity thresholds in dung beetle communities by sampling ten 3,600 ha Atlantic Forest landscapes with forest cover ranging from 5% to 55%. We analysed the response patterns (abundance, gamma and mean alpha diversity) of community subgroups with different levels of forest dependency (forest species, generalist species, and open-area species) using model selection, comparing null, linear, bell-shaped and logistic models. The response of the community of forest species equally fits both linear and logistic models predicting a biodiversity threshold at 25% forest cover. Generalist species showed peak abundance at 20% forest cover although this result reflects a very poor generalist assembly. Open-area specialists did not respond to the amount of forest. The two most plausible models for forest species suggest two different biodiversity management options. Since the biodiversity threshold model represents a more dramatic scenario for the loss of biodiversity in Atlantic forest landscapes, we suggest, based on precautionary principle, that our results should strength guidelines that consider minimum values of forest cover in management strategies to avoid abrupt biodiversity loss and impacts on ecosystem services.

Diet shifts by adult flightless dung beetles Circellium bacchus, revealed using DNA metabarcoding, reflect complex life histories

Life history changes may change resource use. Such shifts are not well understood in the dung beetles, despite recognised differences in larval and adult feeding ability. We use the flightless dung beetle Circellium bacchus to explore such shifts, identifying dung sources of adults using DNA metabarcoding, and comparing these with published accounts of larval dung sources. C. bacchus is traditionally considered to specialise on the dung of large herbivores for both larval and adult feeding. We successfully extracted mammal DNA from 151 adult C. bacchus fecal samples, representing 16 mammal species (ranging from elephants to small rodents), many of which are hitherto undescribed in the diet. Adult C. bacchus showed clear dung source preferences, especially for large herbivores inhabiting dense-cover vegetation. Our approach also confirmed the presence of cryptic taxa in the study area, and we propose that this may be used for biodiversity survey and monitoring purposes. Murid rodent feces were the most commonly fed-upon dung source (77.5%) for adult C. bacchus, differing markedly from the large and megaherbivore dung sources used for larval rearing. These findings support the hypothesis of life history-specific shifts in resource use in dung beetles, and reveal a hitherto unsuspected, but ecologically important, role of these dung beetles in consuming rodent feces. The differences in feeding abilities of the larval and adult life history stages have profound consequences for their resource use and foraging strategies, and hence the ecological role of dung beetles. This principle and its ecological consequences should be explored in other scarabaeids.

High variability of dung beetle diversity patterns at four mountains of the Trans-Mexican Volcanic Belt

Insect diversity patterns of high mountain ecosystems remain poorly studied in the tropics. Sampling dung beetles of the subfamilies Aphodiinae, Scarabaeinae, and Geotrupinae was carried out at four volcanoes in the Trans-Mexican Volcanic Belt (TMVB) in the Mexican transition zone at 2,700 and 3,400 MASL, and on the windward and leeward sides. Sampling units represented a forest–shrubland–pasture (FSP) mosaic typical of this mountain region. A total of 3,430 individuals of 29 dung beetle species were collected. Diversity, abundance and compositional similarity (CS) displayed a high variability at all scales; elevation, cardinal direction, or FSP mosaics did not show any patterns of higher or lower values of those measures. The four mountains were different regarding dispersion patterns and taxonomic groups, both for species and individuals. Onthophagus chevrolati dominated all four mountains with an overall relative abundance of 63%. CS was not related to distance among mountains, but when O. chevrolati was excluded from the analysis, CS values based on species abundance decreased with increasing distance. Speciation, dispersion, and environmental instability are suggested as the main drivers of high mountain diversity patterns, acting together at different spatial and temporal scales. Three species new to science were collected (>10% of all species sampled). These discoveries may indicate that speciation rate is high among these volcanoes—a hypothesis that is also supported by the elevated number of collected species with a restricted montane distribution. Dispersion is an important factor in driving species composition, although naturally limited between high mountains; horizontal colonization events at different time scales may best explain the observed species composition in the TMVB, complemented by vertical colonization events to a lesser extent. Environmental instability may be the main factor causing the high variability of diversity and abundance patterns found during sampling. Together, we interpret these results as indicating that species richness and composition in the high mountains of the TMVB may be driven by biogeographical history while variability in diversity is determined by ecological factors. We argue that current conservation strategies do not focus sufficiently on protecting high mountain fauna, and that there is a need for developing and applying new conservation concepts that take into account the high spatial and temporal variability of this system.

Historical domestication-driven population expansion of the dung beetle Gymnopleurus mopsus (Coleoptera: Scarabaeidae) from its last refuge in Mongolia

Populations of Gymnopleurus mopsus (family Scarabaeidae), a dung beetle that displays dung-rolling behavior (i.e., a telecoprid), have recently experienced sharp declines, and many populations are now at high risk of local extinction. However, Mongolia, which constitutes a major portion of the species' distribution, still sustains a relatively large population. Here, we used mitochondrial COI sequences to investigate the within-population genetic diversity and both the genetic and phylogeographic structures of 24 G. mopsus populations across the species' main distribution in Mongolia. Several lines of evidence indicated that the phylogeographic structure of G. mopsus had been influenced by a recent and sudden demographic expansion. Interestingly, the expansion of Mongolia's G. mopsus population corresponded to the advent of livestock domestication in the region, and the species' genetic structure coincided with road networks, which presumably serve as migration routes for livestock that might mediate the beetle's dispersal. In addition, we also found that G. mopsus possesses high levels of haplotype diversity, which is generally indicative of large effective population sizes (N_e). Overall, the present study contributes to the current understanding of G. mopsus' demographic history and dispersal patterns and also provides valuable information for the species' conservation and management.

JD, Valencia E. Estructura de un ensamblaje de escarabajos coprófagos (Coleoptera: Scarabaeinae) en tres sitios con diferente uso del suelo en Antioquia, Colombia

Los bosques andinos se encuentran sometidos a fuertes procesos de perturbación y fragmentación debido a la creación de pastizales y explotación de monocultivos, especialmente, cafetales. Adicionalmente, es poca la información acerca de la capacidad que tienen estos relictos de bosque para mantener su biodiversidad. Se realizó un estudio en una finca cafetalera-ganadera en el municipio de Tarso (Antioquia), Colombia, utilizando a los escarabajos coprófagos como grupo bioindicador. Se realizaron tres muestreos en tres hábitats: bosque, cafetal y pastizal, cada uno de ellos con un transecto de nueve trampas de caída, cebadas con excremento de cerdo por 48 h. Se recolectaron un total de 779 individuos, distribuidos en 13 especies y 7 géneros. Las especies: Onthophagus curvicornis (n = 196, 25,2%) y Oxysternon conspicillatum (n = 159, 20,4%) fueron las especies dominantes. No hubo diferencias significativas en la riqueza, abundancia, ni en la diversidad entre hábitats, pero si en la biomasa. El ensamblaje estuvo dominado por cavadores, algunos endocópridos y ninguna especie rodadora, evidenciando el alto grado de perturbación del bosque. El cafetal fue el hábitat que presentó la mayor diversidad, posiblemente debido a una mayor oferta alimenticia. Las diferencias entre las biomasas encontradas responden a los procesos de perturbación y fragmentación, ocasionando que el ensamblaje estuviera dominado por O. conspicillatum, lo cual sugiere que la presencia de esta especie en esta localidad sería indispensable para el mantenimiento de la funcionalidad ecosistémica.

Ecological and evolutionary legacy of megafauna extinctions

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna.

Drivers of community assembly in tropical forest restoration sites: role of local environment, landscape, and space

There is increasing recognition that community assembly theory can offer valuable insights for ecological restoration. We studied community assembly processes following tropical forest restoration efforts, using dung beetles (Scarabaeinae) as a focal taxon to investigate taxonomic and functional patterns of biodiversity recovery. We evaluated the relative importance of the local environment (i.e., canopy cover, understory cover, tree basal area, and soil texture), landscape context (i.e., habitat patch proximity and availability and percentage of surrounding area classified as natural forest or Eucalyptus spp. plantation), and space (i.e., spatial proximity of the study areas to estimate dispersal limitation or unmeasured spatially structured processes) on dung beetle species and functional trait composition across a gradient of 15 restoration sites in Brazilian Atlantic Forest. We also assessed which factors were the primary determinants in the establishment of individual dung beetle functional groups, classified according to size, food relocation habit, diet, and period of flight activity. Both species and functional trait composition were most strongly influenced by the local environment, indicating that assembly was predominantly driven by niche-based processes. Most of the variation explained by space was co-explained by local environment and landscape context, ruling out a strong influence of dispersal limitation and random colonization on assembly following restoration. In addition, nearly all of the variance explained by landscape context was co-explained by local environment, suggesting that arrival and establishment at a site depends on both local and landscape-scale environmental factors. Despite strong evidence for niche-based assembly, a large amount of variation remained unexplained in all models, suggesting that stochastic processes and/or unmeasured environmental variables also play an important role. The relative importance of local environment, landscape context, and space changed considerably when analyzing the assembly mechanisms of each functional group separately. Therefore, to recover distinct functional traits in restoration sites, it may be necessary to manipulate different components of the local environment and surrounding landscape. Overall, this study shows that assembly rules can help to better understand recovery processes, enabling improvement of future restoration efforts.

Decline of Ecological Functions Performed by Dung Beetles in Areas of Atlantic Forest and Contribution of Rollers and Tunnellers in Organic Matter Removal

The feeding behavior of the Scarabaeinae subfamily has positive implications on ecosystem functioning. We characterize the necrophagous and coprophagous dung beetle assemblages, and we quantify the removal of swine carrion and domestic dog dung in two areas with different degrees of environmental disturbance in an Atlantic Forest remnant located in Florianopolis, SC, Brazil. The experiment was setup at eight sampling points in each area, by installing one control and two collection and removal assessment arenas for collecting necrophagous dung beetles while simultaneously evaluating the removal of carrion (50 g of rotting pork for 48 h). We used the same sample design with 50 g of domestic dog dung for evaluating the coprophagous dung beetle assemblage and dung removal. Our results indicated that necrophagous dung beetles were more sensitive to environmental disturbance owing to a lower richness and changes in species dominance, which resulted in a lower removal in the areas with greater disturbance and lower environmental quality (39.6% carrion removal) in relation to less disturbed areas (75.1% carrion removal). The dung beetle assemblages were similar in structure and removal rates between areas (80% of dung was removed). In assessing the influence of richness, abundance, and biomass of dung beetles on resource removal both for the whole assemblage and for each separate functional guild, only the abundance and biomass of rollers contributed significantly to dung removal. These results highlight the implications of environmental disturbances on the functions of dung beetles, which respond differently according to the resource they use.

Can dung beetles (Scarabaeinae) indicate the status of Amazonia’s ecosystems? Insights integrating anthropogenic disturbance with seasonal patterns

Temporal and spatial variation in dung beetles abundances is a pattern observed in many tropical forests. The present study evaluated the seasonal patterns of dung beetles in a range of increasingly disturbed ecosystems of the state of Pará, northern Brazil, to identify valuable disturbance indicators. The areas included native forest, agriculture, pasture for extensive livestock grazing and secondary forests. Fieldwork was carried out encompassing the complete range of environmental conditions encountered during the year. In total, 13,649 individuals were captured within 23 genera and 99 species but with pronounced differences among ecosystems and seasons. The obtained results seem to demonstrate that dung beetles can be used to help identify ecosystems under very complex and variable environmental conditions. The ecological drift observed also demonstrates the possibility of using dung beetles as ecological indicators of disturbance in Amazonia.

Wild Herbivore Grazing Enhances Insect Diversity over Livestock Grazing in an African Grassland System

Southern Africa's grassland biodiversity is threatened by habitat transformation such as commercial forestry. Ecological networks (ENs) have been instigated to alleviate the pressure of habitat transformation on local biodiversity. ENs are large scale webs of corridors and patches of natural vegetation criss-crossing production landscapes that can simulate conditions in protected areas (PAs). Many ENs have lost many native large mammal species, which have been replaced by domestic livestock to retain natural grazing dynamics, which could have an impact on the long-term value of ENs for insects. Here we compared dung beetle, butterfly and grasshopper diversity in ENs across a landscape mosaic of timber plantations, where 1) wild megaherbivores were maintained, 2) in ENs where these herbivores were replaced by livestock and, 3) in a nearby World Heritage PA which retained its natural complement of megaherbivores. Sites in the PA far from any plantation were similar in composition to those in the wild grazed EN. Presence of the wild grazers improved the alpha- and beta-diversity of all focal insect taxa when compared to domestic grazing. Furthermore, species composition shows significant differences between the two grazing systems indicating that an assemblage of native large mammals facilitates insect diversity conservation. We support the maintenance or introduction of large native mammals in ENs or similar conservation areas in production landscapes to simulate the ecological conditions and natural heterogeneity in nearby PAs.