Explore the vast range of titles available.

Significance Many suggest we are approaching a sixth mass extinction event, and yet estimates of how many species exist, and thus how many might become extinct, vary by as much as an order of magnitude. There are few statistically robust methods to estimate global species richness, and here we introduce several new methods, including one that builds on the observation that larger species are often described before smaller species. We combine these, giving equal weight to each, to provide mean global species estimates for the most speciose order, class, and phylum on Earth, beetles, insects, and arthropods (terrestrial). We attempt to aid conservation planning by broadening the range of methods used and bringing greater stability to global estimates for these taxa. It has been suggested that we do not know within an order of magnitude the number of all species on Earth [May RM (1988) Science 241(4872):1441–1449]. Roughly 1.5 million valid species of all organisms have been named and described [Costello MJ, Wilson S, Houlding B (2012) Syst Biol 61(5):871–883]. Given Kingdom Animalia numerically dominates this list and virtually all terrestrial vertebrates have been described, the question of how many terrestrial species exist is all but reduced to one of how many arthropod species there are. With beetles alone accounting for about 40% of all described arthropod species, the truly pertinent question is how many beetle species exist. Here we present four new and independent estimates of beetle species richness, which produce a mean estimate of 1.5 million beetle species. We argue that the surprisingly narrow range (0.9–2.1 million) of these four autonomous estimates—derived from host-specificity relationships, ratios with other taxa, plant:beetle ratios, and a completely novel body-size approach—represents a major advance in honing in on the richness of this most significant taxon, and is thus of considerable importance to the debate on how many species exist. Using analogous approaches, we also produce independent estimates for all insects, mean: 5.5 million species (range 2.6–7.8 million), and for terrestrial arthropods, mean: 6.8 million species (range 5.9–7.8 million), which suggest that estimates for the world’s insects and their relatives are narrowing considerably.

Beetles (Coleoptera) are the most diverse and species-rich group of insects, and a robust, time-calibrated phylogeny is fundamental to understanding macroevolutionary processes that underlie their diversity. Here we infer the phylogeny and divergence times of all major lineages of Coleoptera by analyzing 95 protein-coding genes in 373 beetle species, including ~67% of the currently recognized families. The subordinal relationships are strongly supported as Polyphaga (Adephaga (Archostemata, Myxophaga)). The series and superfamilies of Polyphaga are mostly monophyletic. The species-poor Nosodendridae is robustly recovered in a novel position sister to Staphyliniformia, Bostrichiformia, and Cucujiformia. Our divergence time analyses suggest that the crown group of extant beetles occurred ~297 million years ago (Mya) and that ~64% of families originated in the Cretaceous. Most of the herbivorous families experienced a significant increase in diversification rate during the Cretaceous, thus suggesting that the rise of angiosperms in the Cretaceous may have been an ‘evolutionary impetus’ driving the hyperdiversity of herbivorous beetles. The phylogeny of beetles, which represent ~25% of known extant animal species, has been a challenge to resolve. Here, Zhang et al. infer a time-calibrated phylogeny for Coleoptera based on 95 protein-coding genes in 373 species and suggest an association between the hyperdiversification of beetles and the rise of angiosperms.

DNA barcoding-type studies assemble single-locus data from large samples of individuals and species, and have provided new kinds of data for evolutionary surveys of diversity. An important goal of many such studies is to delimit evolutionarily significant species units, especially in biodiversity surveys from environmental DNA samples. The Generalized Mixed Yule Coalescent (GMYC) method is a likelihood method for delimiting species by fitting within- and between-species branching models to reconstructed gene trees. Although the method has been widely used, it has not previously been described in detail or evaluated fully against simulations of alternative scenarios of true patterns of population variation and divergence between species. Here, we present important reformulations to the GMYC method as originally specified, and demonstrate its robustness to a range of departures from its simplifying assumptions. The main factor affecting the accuracy of delimitation is the mean population size of species relative to divergence times between them. Other departures from the model assumptions, such as varying population sizes among species, alternative scenarios for speciation and extinction, and population growth or subdivision within species, have relatively smaller effects. Our simulations demonstrate that support measures derived from the likelihood function provide a robust indication of when the model performs well and when it leads to inaccurate delimitations. Finally, the so-called single-threshold version of the method outperforms the multiple-threshold version of the method on simulated data: we argue that this might represent a fundamental limit due to the nature of evidence used to delimit species in this approach. Together with other studies comparing its performance relative to other methods, our findings support the robustness of GMYC as a tool for delimiting species when only single-locus information is available.

DNA-based species delimitation may be compromised by limited sampling effort and species rarity, including \"singleton\" representatives of species, which hampers estimates of intra-versus interspecies evolutionary processes. In a case study of southern African chafers (beetles in the family Scarabaeidae), many species and subclades were poorly represented and 48.5% of species were singletons. Using cox1 sequences from >500 specimens and ~100 species, the Generalized Mixed Yule Coalescent (GMYC) analysis as well as various other approaches for DNA-based species delimitation (Automatic Barcode Gap Discovery (ABGD), Poisson tree processes (PTP), Species Identifier, Statistical Parsimony), frequently produced poor results if analyzing a narrow target group only, but the performance improved when several subclades were combined. Hence, low sampling may be compensated for by \"clade addition\" of lineages outside of the focal group. Similar findings were obtained in reanalysis of published data sets of taxonomically poorly known species assemblages of insects from Madagascar. The low performance of undersampled trees is not due to high proportions of singletons per se, as shown in simulations (with 13%, 40% and 52% singletons). However, the GMYC method was highly sensitive to variable effective population size (Ne), which was exacerbated by variable species abundances in the simulations. Hence, low sampling success and rarity of species affect the power of the GMYC method only if they reflect great differences in Ne among species. Potential negative effects of skewed species abundances and prevalence of singletons are ultimately an issue about the variation in Ne and the degree to which this is correlated with the census population size and sampling success. Clade addition beyond a limited study group can overcome poor sampling for the GMYC method in particular under variable Ne. This effect was less pronounced for methods of species delimitation not based on coalescent models.

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.

With 400 K described species, beetles (Insecta: Coleoptera) represent the most diverse order in the animal kingdom. Although the study of their diversity currently represents a major challenge, DNA barcodes may provide a functional, standardized tool for their identification. To evaluate this possibility, we performed the first comprehensive test of the effectiveness of DNA barcodes as a tool for beetle identification by sequencing the COI barcode region from 1872 North European species. We examined intraspecific divergences, identification success and the effects of sample size on variation observed within and between species. A high proportion (98.3%) of these species possessed distinctive barcode sequence arrays. Moreover, the sequence divergences between nearest neighbor species were considerably higher than those reported for the only other insect order, Lepidoptera, which has seen intensive analysis (11.99% vs up to 5.80% mean NN divergence). Although maximum intraspecific divergence increased and average divergence between nearest neighbors decreased with increasing sampling effort, these trends rarely hampered identification by DNA barcodes due to deep sequence divergences between most species. The Barcode Index Number system in BOLD coincided strongly with known species boundaries with perfect matches between species and BINs in 92.1% of all cases. In addition, DNA barcode analysis revealed the likely occurrence of about 20 overlooked species. The current results indicate that DNA barcodes distinguish species of beetles remarkably well, establishing their potential to provide an effective identification tool for this order and to accelerate the discovery of new beetle species.

Recent progress in remote sensing provides much-needed, large-scale spatio-temporal information on habitat structures important for biodiversity conservation. Here we examine the potential of a newly launched satellite-borne radar system (Sentinel-1) to map the biodiversity of twelve taxa across five temperate forest regions in central Europe. We show that the sensitivity of radar to habitat structure is similar to that of airborne laser scanning (ALS), the current gold standard in the measurement of forest structure. Our models of different facets of biodiversity reveal that radar performs as well as ALS; median R² over twelve taxa by ALS and radar are 0.51 and 0.57 respectively for the first non-metric multidimensional scaling axes representing assemblage composition. We further demonstrate the promising predictive ability of radar-derived data with external validation based on the species composition of birds and saproxylic beetles. Establishing new area-wide biodiversity monitoring by remote sensing will require the coupling of radar data to stratified and standardized collected local species data. Satellite-borne radar systems are promising tools to obtain spatial habitat data with complete geographic coverage. Here the authors show that freely available Sentinel-1 radar data perform as well as standard airborne laser scanning data for mapping biodiversity of 12 taxa across temperate forests in Germany.

Here, we review the taxonomy and population genetic structure of diving beetles in the genus Liodessus Guignot, 1939 from the high Andes of southern Colombia and Ecuador. Liodessus quillacinga ecuadoriensis ssp. nov. is described from the type locality Otavalo, Laguna San Pablo. Liodessus quimbaya azufralis Megna, Hendrich & Balke, 2019 stat. nov. is now regarded as a subspecies of Liodessus quimbaya Megna, Hendrich & Balke, 2019 based on new morphological and genetical data. Liodessus quimbaya paletara ssp. nov. is described from the Paletará Valley (Colombia: Cauca).

Bacterial communities play a crucial role in the biology, ecology, and evolution of multicellular organisms. In this research, the microbiome of 24 selected beetle species representing five families (Carabidae, Staphylinidae, Curculionidae, Chrysomelidae, Scarabaeidae) and three trophic guilds (carnivorous, herbivorous, detrivorous) was examined using 16S rDNA sequencing on the Illumina platform. The aim of the study was to compare diversity within and among species on various levels of organization, including evaluation of the impact of endosymbiotic bacteria. Collected data showed that beetles possess various bacterial communities and that microbiota of individuals of particular species hosts are intermixed. The most diverse microbiota were found in Carabidae and Scarabaeidae; the least diverse, in Staphylinidae. On higher organization levels, the diversity of bacteria was more dissimilar between families, while the most distinct with respect to their microbiomes were trophic guilds. Moreover, eight taxa of endosymbiotic bacteria were detected including common genera such as Wolbachia, Rickettsia, and Spiroplasma, as well as the rarely detected Cardinium, Arsenophonus, Buchnera, Sulcia, Regiella, and Serratia. There were no correlations among the abundance of the most common Wolbachia and Rickettsia; a finding that does not support the hypothesis that these bacteria occur interchangeably. The abundance of endosymbionts only weakly and negatively correlates with diversity of the whole microbiome in beetles. Overall, microbiome diversity was found to be more dependent on host phylogeny than on the abundance of endosymbionts. This is the first study in which bacteria diversity is compared between numerous species of beetles in a standardized manner.

Beetles represent almost one-fourth of all described species, and knowledge about their relationships and evolution adds to our understanding of biodiversity. We performed a comprehensive phylogenetic analysis of Coleoptera inferred from three genes and nearly 1900 species, representing more than 80% of the world's recognized beetle families. We defined basal relationships in the Polyphaga supergroup, which contains over 300,000 species, and established five families as the earliest branching lineages. By dating the phylogeny, we found that the success of beetles is explained neither by exceptional net diversification rates nor by a predominant role of herbivory and the Cretaceous rise of angiosperms. Instead, the pre-Cretaceous origin of more than 100 present-day lineages suggests that beetle species richness is due to high survival of lineages and sustained diversification in a variety of niches.