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Phylogeny of the Oniticellini and Onthophagini dung beetles (Scarabaeidae, Scarabaeinae) from morphological evidence.

ABSTRACT: A phylogenetic study was conducted to hypothesize relationships of most of the genera of the Oniticellini and Onthophagini for the first time using morphological characters from a diverse array of external and internal sclerites. The monophyly and sister relationship of both tribes was found using Bayesian and parsimony analyses with heavily to moderately weighted data. An alternative hypothesis based on parsimony analyses of unweighted or slightly weighted data show a paraphyletic Oniticellini without the Onthophagini, although recognition of the subtribe Helictopleurina as a tribe would eliminate non-monophyly. Of the three Oniticellini subtribes, the Helictopleurina and Drepanocerina are monophyletic. There is no support for the monophyly of the Oniticellina or the Onthophagini subtribe Alloscelina, as currently defined. The genus Liatongus is paraphyletic, while strong support was found for monophyly of the Madagascan genus, Helictopleurus. The genus Onthophagus is never monophyletic in any analysis performed. Two new subtribes are also proposed: Liatongina subtr. n. including the genus Liatongus and Attavicina subtr. n. including the genera Attavicinus and Paroniticellus. Topological evidence shows that the ancestral oniticellines and onthophagines were all coprophagous with alternative food sources evolving relatively recently. Both myrmecophily and termitophily probably evolved only once in the onthophagines. The phylogenetic analysis supports an African origin for the two tribes, with a relatively early age for the split of the Madagascar helictopleurines from the remaining oniticellines via dispersal. Furthermore, the presence of the oniticellines in the New World is hypothesized to be due to two relatively old dispersal events via Beringia and two relatively recent trans-Atlantic invasions of the Caribbean.

SUBMITTER: Philips TK

PROVIDER: S-EPMC4829968 | biostudies-other | 2016

REPOSITORIES: biostudies-other

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Project description:Scarabaeine dung beetles are the dominant dung feeding group of insects and are widely used as model organisms in conservation, ecology and developmental biology. Due to the conflicts among 13 recently published phylogenies dealing with the higher-level relationships of dung beetles, the phylogeny of this lineage remains largely unresolved. In this study, we conduct rigorous phylogenetic analyses of dung beetles, based on an unprecedented taxon sample (110 taxa) and detailed investigation of morphology (205 characters). We provide the description of morphology and thoroughly illustrate the used characters. Along with parsimony, traditionally used in the analysis of morphological data, we also apply the Bayesian method with a novel approach that uses anatomy ontology for matrix partitioning. This approach allows for heterogeneity in evolutionary rates among characters from different anatomical regions. Anatomy ontology generates a number of parameter-partition schemes which we compare using Bayes factor. We also test the effect of inclusion of autapomorphies in the morphological analysis, which hitherto has not been examined. Generally, schemes with more parameters were favored in the Bayesian comparison suggesting that characters located on different body regions evolve at different rates and that partitioning of the data matrix using anatomy ontology is reasonable; however, trees from the parsimony and all the Bayesian analyses were quite consistent. The hypothesized phylogeny reveals many novel clades and provides additional support for some clades recovered in previous analyses. Our results provide a solid basis for a new classification of dung beetles, in which the taxonomic limits of the tribes Dichotomiini, Deltochilini and Coprini are restricted and many new tribes must be described. Based on the consistency of the phylogeny with biogeography, we speculate that dung beetles may have originated in the Mesozoic contrary to the traditional view pointing to a Cenozoic origin.

Project description:Gut microbes play an important role in the biology and evolution of insects. Australian native dung beetles (Scarabaeinae) present an opportunity to study gut microbiota in an evolutionary context as they come from two distinct phylogenetic lineages and some species in each lineage have secondarily adapted to alternative or broader diets. In this study, we characterised the hindgut bacterial communities found in 21 species of dung beetles across two lineages using 16S rRNA sequencing. We found that gut microbial diversity was more dependent on host phylogeny and gut morphology than specific dietary preferences or environment. In particular, gut microbial diversity was highest in the endemic, flightless genus Cephalodesmius that feeds on a broad range of composted organic matter. The hindgut of Cephalodesmius harbours a highly conserved core set of bacteria suggesting that the bacteria are symbiotic. Symbiosis is supported by the persistence of the core microbiota across isolated beetle populations and between species in the genus. A co-evolutionary relationship is supported by the expansion of the hindgut to form a fermentation chamber and the fermentative nature of the core microbes. In contrast, Australian species of the widespread dung beetle genus Onthophagus, specialise on a single food resource such as dung or fungus, exhibit minimal food processing behaviour, have a short, narrow hindgut and a variable gut microbiota with relatively few core bacterial taxa. A conserved, complex gut microbiota is hypothesised to be unnecessary for this highly mobile genus.IMPORTANCE Dung beetles are a very important part of an ecosystem because of their role in the removal and decomposition of vertebrate dung. It has been suspected that symbiotic gut bacteria facilitate this role, a hypothesis that we have explored with high throughput barcoding. We found that differences in hindgut morphology had the greatest effect on the bacterial community composition. Species with a hindgut fermentation chamber harboured a distinctly different hindgut community compared to those species with a narrow, undifferentiated hindgut. Diet and phylogeny were also associated with differences in gut community. Further understanding of the relationships between dung beetles and their gut microbes will provide insights into the evolution of their behaviours and how gut communities contribute to their fitness.

Project description:Background Increasing temperatures and changes in precipitation patterns threaten the existence of many organisms. It is therefore informative to identify the functional traits that underlie differences in desiccation resistance to understand the response of different species to changes in water availability resulting from climate change. We used adult dung beetles as model species due to their importance to ecosystem services. We investigated: (i) the effect of physiological (water loss rate, water loss tolerance, body water content), morphological (body mass) and ecological (nesting behaviour) traits on desiccation resistance; (ii) the role of phylogenetic relatedness in the above associations; and, (iii) whether relatively large or small individuals within a species have similar desiccation resistance and whether these responses are consistent across species. Results Desiccation resistance decreased with increasing water loss rate and increased with increasing water loss tolerance (i.e. proportion of initial water content lost at the time of death). A lack of consistent correlation between these traits due to phylogenetic relatedness suggests that the relationship is not determined by a shared evolutionary history. The advantage of a large body size in favouring desiccation resistance depended on the nesting behaviour of the dung beetles. In rollers (one species), large body sizes increased desiccation resistance, while in tunnelers and dwellers, desiccation resistance seemed not to be dependent on body mass. The phylogenetic correlation between desiccation resistance and nesting strategies was significant. Within each species, large individuals showed greater resistance to desiccation, and these responses were consistent across species. Conclusions Resistance to desiccation was explained mainly by the dung beetles’ ability to reduce water loss rate (avoidance) and to tolerate water loss (tolerance). A reduction in water availability may impose a selection pressure on body size that varies based on nesting strategies, even though these responses may be phylogenetically constrained. Changes in water availability are more likely to affect dweller species, and hence the ecosystem services they provide. Supplementary Information The online version contains supplementary material available at 10.1186/s40850-021-00089-3.

Project description:Wildlife as a source of microbial contamination is a food safety concern. Deer feces (scat) have been determined as a point source for Escherichia coli O157:H7 contamination of fresh produce. The ecological role of the scooped scarab (Onthophagus hecate (Panzer)), a generalist dung beetle species common in Maine blueberry fields, was explored as a biological control agent and alternatively as a pathogen vector between deer scat and food. A large-scale field survey of wildlife scat indicated that pathogenic E. coli O157:H7 was present, albeit at a low prevalence (1.9% of samples, n = 318), in the Maine lowbush blueberry agroecosystem. A manipulative field experiment verified that, should contact occur between deer scat and blueberry plants and fruit during the summer, contamination with E. coli O157:H7 can occur and persist for more than 72 h. For both the positive control and an experimental scat inoculation treatment, the levels of the bacterial population decreased over time, but at different rates (treatment x time interaction: F (1.9,18.8) = 358.486, P < 0.0001). The positive control inoculation, which resulted in a higher initial E. coli level on fruit, decayed at a faster rate than inoculation of fruit via scat in the experimental treatment. We conducted 2 laboratory studies to elucidate aspects of dung beetle feeding ecology as it relates to suppression of E. coli O157:H7 from deer scat to lowbush blueberry fruit. In both experiments, dung beetles buried the same amount of scat whether or not the scat was inoculated with the pathogen (F(1,6) = 0.001; P = 0.999 and (F (2,17) = 4.10, P = 0.147). Beetles feeding on E. coli inoculated deer scat were not found to vector the pathogen to fruit. In two studies, beetles lowered the amount of pathogenic E. coli persisting in soils compared to soils without beetles (F (2,9) = 7.757; P = 0.05 and F (2,17) = 8.0621, P = 0.004). Our study suggests that the dung beetle species, Onthophagus hecate, has the potential to contribute to the suppression of E. coli O157:H7 in agricultural landscapes.

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Phylogeny of the Oniticellini and Onthophagini dung beetles (Scarabaeidae, Scarabaeinae) from morphological evidence.

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