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.

Phylogenetic relationships in the coleopteran Series Elateriformia (click beetles, jewel beetles, fireflies and allies) were investigated using > 3800 nucleotides of partial nuclear (small and large subunit rRNA genes) and mitochondrial (large subunit rRNA and cytochrome oxidase subunit I) gene sequences. The Elateriformia includes several soft-bodied lineages, some of which retain larviform features in the adult stage (neoteny), and several major bioluminescent groups, including the families Lampyridae (fireflies), Phengodidae and Rhagophthalmidae whose relationships have been contentious. All recognized superfamilies (Elateroidea, Cantharoidea, Byrrhoidea, Buprestoidea, Dascilloidea, Scirtoidea) and 28 of the 37 families, represented in 112 individuals, were included in the analysis. Sequence alignment was based on static and dynamic homology assignments and partial removal of sequences of uncertain homology. Alignment variable regions caused a great deal of uncertainty but also contributed much of the phylogenetic signal that was insufficient to resolve deep relationships when these were removed. The main features of most analyses were the monophyly of Elateroidea + Cantharoidea (¼ Elateroidea sensu lato), with Omethidae + Telegeusidae frequently occupying the basal node in this group; the affinities of Dascilloidea, Buprestoidea and a (broadly paraphyletic) Byrrhoidea, with unclear relationships among them; and the monophyly of Scirtoidea (including Decliniidae) as a rather distant outgroup to all others. When mapped on the resulting trees, soft-bodied lineages were polyphyletic, contradicting the former Cantharoidea that had been united by this trait. Transitions to neoteny were either simultaneous with, or subsequent to, the origin of soft-bodiedness in a minimum of seven lineages. The bioluminescent groups Lampyridae (including the enigmatic genus Drilaster) and the tightly allied Phengodidae + Rhagophthalmidae were never monophyletic. The former showed close relationship to the species-rich, soft-bodied families Lycidae and Cantharidae, while the latter grouped with poorly resolved lineages at the base of Elateridae (click beetles). Hence, although key features as soft-bodiedness, neoteny and bioluminescence in Coleoptera are largely confined to the Elateriformia, they appear to result from multiple origins, showing the propensity of closely related lineages to acquire similar features independently.

Neoteny, the maintenance of larval features in sexually mature adults, is a radical way of generating evolutionary novelty through shifts in relative timing of developmental programmes. While controlled by the environment in facultative neotenics, retention of larval features is obligatory in many species of Lycidae (net-winged beetles). They are studied here as an example of how developmental shifts and ecology interact to produce macroevolutionary impacts. We conducted a phylogenetic analysis of Lycidae based on DNA sequences from nuclear (18S and 28S rRNA) and mitochondrial (rrnL, cox1, cob and nad5) genes from a representative set of lineages (73 species), including 17 neotenic taxa. Major changes of basal relationships compared with those implied in the current classification generally supported three independent origins of neotenics in Lycidae. The southeast Asian Lyropaeinae and Ateliinae were in basal positions indicating evolutionary antiquity, also confirmed by molecular clock estimates, unlike the neotropical leptolycines nested within Calopterini and presumably much younger. neotenics exhibit typical K-selected traits including slow development, large body size, high investment in offspring and low dispersal. This correlated with low species richness and restricted ranges of neotenic lineages compared with their sisters. Yet, these factors did not impede the evolutionary persistence of affected lineages, even without reversals to fully metamorphosed forms, contradicting earlier suggestions of recent evolution from dispersive non-neotenics.

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BackgroundRhinorhipidae Lawrence, 1988 is an enigmatic beetle family represented by a single species, Rhinorhipus tamborinensis Lawrence, 1988, from Australia, with poorly established affinities near the superfamily Elateroidea (click beetles, soldier beetles and fireflies) or the more inclusive series (infraorder) Elateriformia. Its evolutionary position may inform the basal relationships of the suborder Polyphaga, the largest clade of Coleoptera.ResultsWe analyzed four densely sampled DNA datasets of major coleopteran lineages for mitogenomes, rRNA genes and single copy nuclear genes. Additionally, genome sequencing was used for incorporation of R. tamborinensis into a set of 4220 orthologs for 24 terminals representing 12 polyphagan superfamilies. Topologies differed to various degrees, but all consistently refute the proposed placement of Rhinorhipidae in Elateroidea and instead indicate either sister relationships with other Elateriformia, frequently together with Nosodendridae, another divergent small family hitherto placed in Derodontoidea, or in an isolated position among the deepest lineages of Polyphaga. The phylogenomic analyses recovered Rhinorhipus in a sister position to all other Elateriformia composed of five superfamilies. Therefore, we erect the new superfamily Rhinorhipoidea Lawrence, 1988, stat. Nov., with the type-family Rhinorhipidae. The origins of the Rhinorhipidae were dated to the Upper Triassic/Lower Jurassic at the very early phase of polyphagan diversification.ConclusionsThus, Rhinorhipidae adds another example to several recently recognized ancient relict lineages which are interspersed within contemporaneous hugely species-rich lineages of Coleoptera.Electronic supplementary materialThe online version of this article (10.1186/s12983-018-0262-0) contains supplementary material, which is available to authorized users.

The melyrid lineage of beetles form a distinct group of the superfamily Cleroidea with a high level of soft‐bodiedness. Here we present the first molecular phylogenetic analysis of this group. The data matrix included partial sequences of the small and large subunits of rRNA, the mitochondrial large subunit rRNA, and cytochrome oxidase subunit I of 67 melyrid and eight outgroup taxa. The concatenated sequences were analysed using maximum‐parsimony (MP), maximum‐likelihood (ML) and Bayesian analysis (BA) approach. The results strongly supported the monophyly of the melyrid lineage splitting into six major clades: Rhadalidae, Mauroniscidae, Prionoceridae, Melyridae sensu stricto, Dasytidae and Malachiidae. The rhadalids were placed in the most basal position, followed by mauroniscids and prionocerids. Three terminal lineages—the true melyrids, dasytids, and malachiids—are well supported by all analyses, but their mutual relationships remain uncertain as MP analysis proposed alternative topologies to that of the ML and BA trees, with often low node support in the latter two methods. The monophyly of the subfamily Danacaeinae (Dasytidae) with respect to the danacaeine genera of the southern hemisphere (Hylodanacaea, Listrocerus, Amecocerus) was challenged as they were found to be polyphyletic. Similarly, the monophyly of Attalus was rejected by our analyses and shown to be polyphyletic. Based on the preferred phylogenetic hypothesis, the subfamilies Rhadalinae, Dasytinae and Malachiinae are elevated to family rank. © The Willi Hennig Society 2011.

The relationships of the monogeneric family Plastoceridae Crowson, 1972 (Coleoptera: Elateroidea) have remained contentious due to its modified morphology, incorrect information on incomplete metamorphosis of females and the absence of molecular data. We produced the sequences for P. angulosus (Germar, 1844) (the type-species of Plastocerus Schaum, 1852) and performed molecular phylogenetic analyses to estimate its position. The analyses of Elateroidea (186 spp.) and Elateridae (110 spp.) molecular datasets of two mitochondrial and two nuclear gene fragments repeatedly placed Plastocerus Schaum, 1852 in relationships with the elaterid genera Oxynopterus Hope, 1842 and Pectocera Hope, 1842. Alternative topologies were rejected by likelihood tests. Therefore, Plastoceridae Crowson, 1972 are down-ranked to the subfamily Plastocerinae in Elateridae Leach, 1815. We suggest that the morphology-based placement and high rank for some elateroid lineages were inferred from the presence of homoplasies which evolved due to incomplete sclerotization. Distantly related soft-bodied elateroids share freely movable and transverse coxae, a shortened prosternum, and a weakly sclerotized abdomen with free ventrites. Importantly, the apomorphic structures characteristic for their closest relatives, such as the prosternal process, mesoventral cavity, and intercoxal keel in the first abdominal ventrite are regularly absent. Consequently, morphology-based phylogenetic analyses suggest deeply rooted positions for lineages without expressed apomorphic character states. Molecular data represent an independent character system that is not affected by the convergent morphological evolution, and therefore molecular phylogenies can elucidate the relationships of incompletely sclerotized lineages.