High-throughput DNA sequencing has the potential to accelerate species discovery if it is able to recognize evolutionary entities from sequence data that are comparable to species. The general mixed ...Yule-coalescent (GMYC) model estimates the species boundary from DNA surveys by identifying independently evolving lineages as a transition from coalescent to speciation branching patterns on a phylogenetic tree. Applied here to 12 families from 4 orders of insects in Madagascar, we used the model to delineate 370 putative species from mitochondrial DNA sequence variation among 1614 individuals. These were compared with data from the nuclear genome and morphological identification and found to be highly congruent (98% and 94%). We developed a modified GMYC that allows for a variable transition from coalescent to speciation among lineages. This revised model increased the congruence with morphology (97%), suggesting that a variable threshold better reflects the clustering of sequence data into biological species. Local endemism was pronounced in all 5 insect groups. Most species (60–91%) and haplotypes (88–99%) were found at only 1 of the 5 study sites (40–1000 km apart). This pronounced endemism resulted in a 37% increase in species numbers using diagnostic nucleotides in a population aggregation analysis. Sample sizes between 7 and 10 individuals represented a threshold above which there was minimal increase in genetic diversity, broadly agreeing with coalescent theory and other empirical studies. Our results from > 1.4 Mb of empirical data suggest that the GMYC model captures species boundaries comparable to those from traditional methods without the need for prior hypotheses of population coherence. This provides a method of species discovery and biodiversity assessment using single-locus data from mixed or environmental samples while building a globally available taxonomic database for future identifications.
Insects are involved in the biogeochemical cycles of multiple elements and influence soil fertility. In particular, soil insects and the functions that they support can affect the response of ...terrestrial ecosystems to environmental changes. We experimentally studied the role of dung beetles as recyclers of cow dung in drylands of the Central Monte in mid-western Argentina; and we extrapolated these results to ecosystem impact in a grazing field, considering the dung beetle's abundance in summer. We conducted experiments with four species of dung beetles (Sulcophanaeus imperator, Eucranium arachnoides, Digitonthophagus gazella and Malagoniella puncticollis), and quantified their abundance on the field. Dung beetles incorporated nitrogen, ammonium, and phosphorous to the soil, but this activity varied substantially among species. The highest quantity of organic matter, nitrogen and phosphate was incorporated to the soil by S. imperator, one of the larger beetle studied. While the per capita effect of S. imperator is superior to other species studied, the impact on the ecosystem of the invasive D. gazella might be superior due to their major abundance in grazing fields. Our results highlight the importance of considering both components, per capita effect and abundance, to estimate with more reliability the relative importance of dung beetle species. Given that the effect of dung beetles on nutrient cycling is variable among species, and their abundance is variable in space, it is important to conserve beetle diversity in order to maximize their beneficial impacts on soils. Therefore, dung beetle effect on soil might be crucial in drylands to mitigate the nitrogen losses caused by grazing.
•Dung beetles incorporated nitrogen, ammonium and phosphorous to the soil.•Nutrient incorporation to the soil varied substantially among study species.•Ecosystem impact of different dung beetle species varies according to per capita effect and abundance.•Dung beetles play an important ecological role in drylands.
•Hundreds of arthropod species were found in dung from eastern South Dakota.•Avermectin in dung lowered dung beetle abundance.•Replacing avermectin with frequent, high intensity grazing fostered dung ...arthropods.•Herd management mimicking ancestral grazing favored dung biota biodiversity.
Agroecosystems represent a large geographical footprint in most terrestrial landscapes, and management decisions within these systems affect their function in species conservation. We evaluated the effects that rangeland management systems (based on stocking density, rotation frequency, and the number of avermectin applications) have on conserving the dung arthropod community in the Northern Great Plains of North America. Comprehensive bioinventories of arthropods were collected from 16 rangelands using core samples of dung pats. Ivermectin was quantified in pats from each ranch using enzyme-linked immunosorbant assay (ELISA). Arthropods in dung were abundant (116,244 specimens) and diverse in eastern South Dakota (172 morphospecies). Rangelands managed with more regenerative practices (frequent rotation at high stocking densities and lack of ivermectin applications) had greater species richness, diversity, predator species abundance, and dung beetle abundance than more conventionally managed rangelands. Ivermectin quantity in cattle pats was negatively correlated with dung beetle abundance and diversity. This work shows that herd management (specifically high-intensity, frequent rotational grazing and eliminating prophylactic ivermectin use) that aims to mimic intensive grazing of large migrating herds of ruminants can foster dung arthropod community structure, a key trait correlated with nutrient cycling, pest suppression, and productivity of cattle-grazed rangelands.
Dung beetles (subfamily Scarabaeinae) are popular model organisms in ecology and developmental biology, and for the last two decades they have experienced a systematics renaissance with the adoption ...of modern phylogenetic approaches. Within this period 16 key phylogenies and numerous additional studies with limited scope have been published, but higher-level relationships of this pivotal group of beetles remain contentious and current classifications contain many unnatural groupings. The present study provides a robust phylogenetic framework and a revised classification of dung beetles.
We assembled the so far largest molecular dataset for dung beetles using sequences of 8 gene regions and 547 terminals including the outgroup taxa. This dataset was analyzed using Bayesian, maximum likelihood and parsimony approaches. In order to test the sensitivity of results to different analytical treatments, we evaluated alternative partitioning schemes based on secondary structure, domains and codon position. We assessed substitution models adequacy using Bayesian framework and used these results to exclude partitions where substitution models did not adequately depict the processes that generated the data. We show that exclusion of partitions that failed the model adequacy evaluation has a potential to improve phylogenetic inference, but efficient implementation of this approach on large datasets is problematic and awaits development of new computationally advanced software. In the class Insecta it is uncommon for the results of molecular phylogenetic analysis to lead to substantial changes in classification. However, the results presented here are congruent with recent morphological studies and support the largest change in dung beetle systematics for the last 50 years. Here we propose the revision of the concepts for the tribes Deltochilini (Canthonini), Dichotomiini and Coprini; additionally, we redefine the tribe Sisyphini. We provide and illustrate synapomorphies and diagnostic characters supporting the new concepts to facilitate diagnosability of the redefined tribes. As a result of the proposed changes a large number of genera previously assigned to these tribes are now left outside the redefined tribes and are treated as incertae sedis.
The present study redefines dung beetles classification and gives new insight into their phylogeny. It has broad implications for the systematics as well as for various ecological and evolutionary analyses in dung beetles.
Dryland cattle pastures often yield sub-optimal economic returns while it intervenes with natural ecosystems functioning. Dung beetles improve soil conditions but little is known about how their ...functioning changes with different land management intensities. We assessed the role of the telecoprid dung beetle Canthon humectus in soil nutrient mobilization and commercial crop growth in arid grasslands with contrasting cattle managements. We set up a mesocosm experiment where we monitored dung beetle activity in containers filled with dung and soil from sites with three different cattle managements. Dung removal rates due to beetle burial activity were 10% higher than due to dehydration alone but was not affected by cattle management. After 60 days of beetle activity nitrates and ammonium levels increased significantly as compared with control pots without beetles. Additionally, we monitored corn plant growth in pots with soil with and without beetle activity. Plants significantly increased their biomass due to beetle activity in the substrate with the highest and lowest pasture management intensity. In the latter case, more biomass was allocated to shoots. The ability of C. humectus to increase soil nutrients and enhance plant growth is affected by local cattle management.
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•Telecoprid dung beetle activity increases soil nitrogen and ammonium.•Plant growth is accelerated in soils with dung beetle activity.•Dung beetle function of C. humectus changes with grassland management intensity.
Abstract
Nestedness is widely observed in natural metacommunities, but its underlying mechanisms are still poorly understood. The distribution of habitats in the landscape and differences in ...dispersal rates of distinct insect taxa can determine the nestedness of the metacommunity. Here, we evaluated how species habitat specialization contributes to metacommunity nestedness in insect groups with different dispersal capacities in a mountaintop landscape in south-eastern Brazil. We sampled ants, butterflies and dung beetles in two main habitats, naturally fragmented forest islands and a grassland matrix (campo rupestre), during both dry and rainy seasons. We classified species according to their degree of habitat specialization (generalists or specialists) based on the relative frequencies and abundances between these two contrasting habitats. Forty of 211 species were classified as habitat specialists, seven as habitat generalists. It was not possible to classify the remaining species. The metacommunity was nested in structure, with habitat generalist species contributing more to nestedness than habitat specialists. Nonetheless, habitat distribution in the landscape did not affect the nestedness of the metacommunity. Our findings reveal that species sorting (for habitat specialists) and mass effects (for habitat generalists) are concurrent processes in the mountaintop forest–grassland mosaic. Our study helps to advance our understanding of the differences in the distribution of generalist and specialist species in a tropical mountaintop landscape and improves our ability to predict and manage the increasingly adverse effects of changes in land use and climate on metacommunities and ecosystem functions.
The impact of large herbivores on ecosystems before modern human activities is an open question in ecology and conservation. For Europe, the controversial wood—pasture hypothesis posits that grazing ...by wild large herbivores supported a dynamic mosaic of vegetation structures at the landscape scale under temperate conditions before agriculture. The contrasting position suggests that European temperate vegetation was primarily closed forest with relatively small open areas, at most impacted locally by large herbivores. Given the role of modern humans in the world-wide decimations of megafauna during the late Quaternary, to resolve this debate it is necessary to understand herbivore—vegetation interactions before these losses. Here, a synthetic analysis of beetle fossils from Great Britain shows that beetles associated with herbivore dung were better represented during the Last Interglacial (132,000—110,000 y B.P., before modern human arrival) than in the early Holocene (10,000—5,000 y B.P.). Furthermore, beetle assemblages indicate closed and partially closed forest in the early Holocene but a greater mixture of semiopen vegetation and forest in the Last Interglacial. Hence, abundant and diverse large herbivores appear to have been associated with high structural diversity of vegetation before the megafauna extinctions at the end of the Pleistocene. After these losses and in the presence of modern humans, large herbivores generally were less abundant, and closed woodland was more prevalent in the early Holocene. Our findings point to the importance of the formerly rich fauna of large herbivores in sustaining structurally diverse vegetation in the temperate forest biome and provide support for recent moves toward rewilding-based conservation management.
Describes a collaboration between scientists and an artist focussing on the dung beetle. Explains the relationship between soil and dung in pastoral New Zealand, provides a background on dung beetles ...and discusses the release of dung beetles into New Zealand. Source: National Library of New Zealand Te Puna Matauranga o Aotearoa, licensed by the Department of Internal Affairs for re-use under the Creative Commons Attribution 3.0 New Zealand Licence.
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