Basal relationships of Coleoptera inferred from 18S rDNA sequences

The basal relationships of the hyperdiverse insect order Coleoptera (beetles) have proven difficult to resolve. Examination of beetle suborder relationships using 18S ribosomal DNA reveals a previously unproposed relationship among the four major lineages: [(Archostemata(Myxophaga(Adephaga, Polyphaga)))]. Adding representatives of most other insect orders results in a non-monophyletic Coleoptera. However, constraining Coleoptera and its suborders to be monophyletic, in analyses of beetle and outgroup sequences, also results in the above beetle relationships, with the root placed between Archostemata and the remaining suborders.     

The thoracic morphology of Archostemata and the relationships of the extant suborders of Coleoptera (Hexapoda)

Thoracic structures of Tetraphalerus bruchi are described in detail. The results were compared with features found in other representatives of Archostemata and other coleopteran suborders. Differences between thoracic structures of Tetraphalerus and members of other archostematan subgroups are discussed. External and internal characters of larval and adult representatives of 37 genera of the coleopteran suborders are outlined, coded and analysed cladistically, with four groups of Neuropterida as outgroup taxa. The results strongly suggest the branching pattern Archostemata + [Adephaga + (Myxophaga + Polyphaga)]. Coleoptera excluding Archostemata are supported with a high Bremer support. Important evolutionary changes linked with this branching event are simplifications of the thoracic skeleton resulting in reduced degrees of freedom (i.e. a restricted movability, especially at the leg bases), and a distinct simplification of the muscle system. This development culminates in Polyphaga, which are also strongly supported as a clade. Internalization of the partly reduced propleura, further muscle losses, and the fusion of the mesoventrites and metaventrites—with reversal in Scirtoidea and Derodontidae—are autapomorphies of Polyphaga. Archostemata is a small relict group in contrast to highly successful xylobiontic groups of Polyphaga. The less efficient thoracic locomotor apparatus, the lack of cryptonephric Malpighian tubules, and the rise of angiosperms with beetle groups primarily adjusted to them may have contributed to the decline of Archostemata.
© The Willi Hennig Society 2008.     

Monophyly of terrestrial adephagan beetles as indicated by three nuclear genes (Coleoptera: Carabidae and Trachypachidae)

The beetle suborder Adephaga is traditionally divided into two sections on the basis of habitat, terrestrial Geadephaga and aquatic Hydradephaga. Monophyly of both groups is uncertain, and the relationship of the two groups has implications for inferring habitat transitions within Adephaga. Here we examine phylogenetic relationships of these groups using evidence provided by DNA sequences from all four suborders of beetles, including 60 species of Adephaga, 4 Archostemata, 3 Myxophaga, and 10 Polyphaga. We studied 18S ribosomal DNA and 28S ribosomal DNA, aligned with consideration of secondary structure, as well as the nuclear protein-coding gene wingless . Independent and combined Bayesian, likelihood, and parsimony analyses of all three genes supported placement of Trachypachidae in a monophyletic Geadephaga, although for analyses of 28S rDNA and some parsimony analyses only if Coleoptera is constrained to be monophyletic. Most analyses showed limited support for the monophyly of Hydradephaga. Outside of Adephaga, there is support from the ribosomal genes for a sister group relationship between Adephaga and Polyphaga. Within the small number of sampled Polyphaga, analyses of 18S rDNA, wingless , and the combined matrix supports monophyly of Polyphaga exclusive of Scirtoidea. Unconstrained analyses of the evolution of habitat suggest that Adephaga was ancestrally aquatic with one transition to terrestrial. However, in analyses constrained to disallow changes from aquatic to terrestrial habitat, the phylogenies imply two origins of aquatic habit within Adephaga.     

Phylogenetic analyses and evolutionary timescale of Coleoptera based on mitochondrial sequence

Coleopteran phylogeny was analysed using mitochondrial genome (mitogenome) sequence. The optimal tree topology was given by the dataset consisted of all coding genes except for the exclusion of the 3rd codon sites (mtDNA12) using Bayesian Inference Method. This topology supports the monophyly of four suborders, and the sister group relationship between Adephaga and Myxophaga and between Polyphaga and Archostemata. In Polyphaga, Cucujiformia and Elateroidea formed independent node respectively, the remaining species grouped together except for Cyphon sp, among which, only Cucujiformia and Scarabaeiformia were supported as monophyletic group, respectively. Within Cucujiformia, the monophyly of Chrysomeloidea, Curculionoidea and Tenebrionoidea were supported respectively, among which Tenebrionoidea occupied the basal position of Cucujiformia. Cleroidea grouped together with Bothrideridae and Coccinellidae, and formed an independent node, which lead to the paraphyly of Cucujoidea. The monophyly of Elateriformia was not supported because of the division of Scirtoidea and Buprestoidea. Furthermore, using a Bayesian relaxed clock calibrated with fossil data, we estimated that most superfamilies within Polyphaga originated in the Jurassic period.     

Sequence alignment of 18S ribosomal RNA and the basal relationships of Adephagan beetles: evidence for monophyly of aquatic families and the placement of Trachypachidae

Current hypotheses regarding family relationships in the suborder Adephaga (Coleoptera) are conflicting. Here we report full-length 18S ribosomal RNA sequences of 39 adephagans and 13 outgroup taxa. Data analysis focused on the impact of sequence alignment on tree topology, using two principally different approaches. Tree alignments, which seek to minimize indels and substitutions on the tree in a single step, as implemented in an approximate procedure by the computer program POY, were contrasted with a more traditional procedure based on alignments followed by phylogenetic inference based on parsimony, likelihood, and distance analyses. Despite substantial differences between the procedures, phylogenetic conclusions regarding basal relationships within Adephaga and relationships between the four suborders of Coleoptera were broadly similar. The analysis weakly supports monophyly of Adephaga, with Polyphaga usually as its sister, and the two small suborders Myxophaga and Archostemata basal to them. In some analyses, however, Polyphaga was reconstructed as having arisen from within Hydradephaga. Adephaga generally split into two monophyletic groups, corresponding to the terrestrial Geadephaga and the aquatic Hydradephaga, as initially proposed by Crowson in 1955, consistent with a single colonization of the aquatic environment by adephagan ancestors and contradicting the recent proposition of three independent invasions. A monophyletic Hydradephaga is consistently, though not strongly, supported under most analyses, and a parametric bootstrapping test significantly rejects an hypothesis of nonmonophyly. The enigmatic Trachypachidae, which exhibit many similarities to aquatic forms but whose species are entirely terrestrial, were usually recovered as a basal lineage within Geadephaga. Strong evidence opposes the view that terrestrial trachypachids are related to the dytiscoid water beetles.     

The head morphology of Clambidae and its implications for the phylogeny of Scirtoidea (Coleoptera: Polyphaga)

External and internal structures of the head of adults of Clambus are described and illustrated in detail. The results are compared with structural features found in the clambid genus Calyptomerus, in representatives of other scirtoid families, and also in species of other coleopteran suborders, notably Myxophaga. The results tentatively support the monophyly of Scirtoidea and a close relationship between Clambidae and Eucinetidae is suggested by one shared derived feature of the mandible, a long and slender apical tooth with a serrate edge. The monophyly of Clambidae is very strongly supported and Acalyptomerus is probably the sistergroup of a clade Calyptomerus + Clambinae. Potential scirtoid autapomorphies are the loss of the dorsal tentorial arms, a bulging gula, a strongly transverse labrum, and a ridge separating the mediostipes from the lacinia. However, all these features are homoplasious. The monophyly of Clambidae is supported by modifications of the head capsule which is strongly flattened and broadened, by a deep clypeofrontal incision enabling vertical antennal movements, and a series of antennal features. Synapomorphies of Clambinae + Calyptomerus (Clambidae excluding Acalyptomerus) are the conglobate body form with the ventral side of the head capsule in contact with the mesocoxae, and compound eyes integrated in the contour of the head. The completely subdivided eye is an autapomorphy of Clambus. An entire series of features is shared by Clambidae (or Scirtoidea) and Myxophaga. Most of them are apomorphies that apparently evolved independently in both groups. However, the presence of well‐developed maxillary and labial glands is arguably a retained groundplan feature of Coleoptera, with parallel loss in Archostemata, Adephaga and various groups of Polyphaga. J. Morphol. 277:615–633, 2016. © 2016 Wiley Periodicals, Inc.     

Phylogenetic analysis of Staphyliniformia (Coleoptera) based on characters of larvae and adults

Abstract. One hundred and twenty-one morphological characters of larvae and adults of the series Staphyliniformia were scored (multistate coding) and analysed to determine the family group relationships of the polyphagan groups Scarabaeoidea, Histeroidea, Hydrophiloidea and Staphylinoidea. Cladograms were rooted with exemplars of Adephaga, Archostemata, Myxophaga and the polyphagan families Dascillidae, Derodontidae, Eucinetidae and Scirtidae. Analyses of the same dataset with multistate characters re-coded as presence/absence (144 characters) produced cladograms that were similar to those produced from analyses of the original characters. Cladograms produced from partitioned larval and adult characters differed strongly, with adult-only trees more similar to those produced by combined data. The results confirm the monophyly of Hydrophiloidea + Histeroidea and of Staphylinoidea (including Hydraenidae). The Epimetopidae + Georissidae are the only strongly supported clade within Hydrophiloidea. A clade comprising Hydrochidae, Spercheidae and Hydrophilidae, and a sister-group relationship between the latter two families were confirmed in analyses of the data with presence/absence coding. Helophoridae, Epimetopidae and Georissidae are probably not a monophyletic unit, and additional evidence is needed for a reliable placement of Helophoridae. Scarabaeoidea are placed as a sister taxon of Hydrophiloidea + Histeroidea, but support for this relationship is weak. The branching pattern ((Hydraenidae + Ptiliidae) + (Leiodidae + Agyrtidae)), and a clade comprising Scydmaenidae, Silphidae and Staphylinidae (= ‘staphylinid group’) are well founded. The branching pattern (Orchymontiinae + (Prosthetopinae + (Ochthebiinae + Hydraeninae))) within Hydraenidae is confirmed. Poor resolution at the base of the trees and the placement of some nonstaphyliniform taxa (Dascillidae, Derodontidae, Scirtidae and Eucinetidae) as a sister group to a clade comprising Scarabaeoidea, Hydrophiloidea and Histeroidea suggests that Staphyliniformia may be paraphyletic. It is recommended that series names are eliminated from the classification of Polyphaga, at least for the more ‘primitive’ groups.     

鞘翅目高级阶元分子系统学： 研究现状及存在的问题

鞘翅目是世界上物种最丰富的类群, 分为原鞘亚目（Archostemata Kolbe, 1908）、 藻食亚目（Myxophaga Crowson, 1955）、 肉食亚目（Adephaga Schellenberg, 1806）和多食亚目（Polyphaga Emery, 1886）。随着分子生物学的发展,分子系统学的技术被广泛应用于鞘翅目系统学研究中。本文综述了鞘翅目高级阶元的分子系统学的研究进展及存在问题。基于分子生物学手段, 分子分类学家提出了关于鞘翅目高级阶元分子系统学很多假说, 分子分析结果支持鞘翅目的4个亚目各为单系, 而亚目间的系统关系还不统一。基于分子手段对于亚目内的系统发育关系的研究也有了一定的进展, 比如： 分子系统学结果支持肉食亚目的水生类群和陆生类群分别为单系, 水生类群为一次起源。目前, 鞘翅目高级阶元分子系统学的研究还不够成熟和完善, 主要表现为： 材料选择有限且不均衡、 基因数目和适合度不理想, 以及一些关键节点研究的欠缺。     

On the head morphology of Tetraphalerus, the phylogeny of Archostemata and the basal branching events in Coleoptera

Internal and external features of Tetraphalerus bruchi were studied using X‐ray microtomography (µ‐CT) and other techniques, and head structures were described in detail. µ‐Ct is highly efficient for the assessment of anatomical data. A data matrix with 90 morphological characters of recent and fossil beetles was analyzed with different approaches (parsimony, Bayesian analysis). The results of the parsimony analysis resulted in the following branching pattern: (?Tshekardocoleidae + (?Permocupedidae, ?Rhombocoleidae + (?Triadocupedidae + ((Adephaga + (Myxophaga + Polyphaga))) + Archostemata s.str. [including Jurodidae]))). Sikhotealinia is placed as sister group of ?Jurodes (Jurodidae), and Jurodidae as sister group of the remaining Archostemata (Bayesian analysis) or of a clade comprising Micromalthidae, Crowsoniellidae, ?Ademosynidae, ?Schizophoridae and ?Catiniidae. The monophyly of Ommatidae and Cupedidae is well supported and Priacma is placed as the sister group of all other Cupedidae. Important events in the early evolution of Coleoptera are the shortening of the elytra and the transformation of the elytral venation (Coleoptera excluding ?Tshekardocoleidae), the formation of a closed subelytral space (Coleoptera excluding ?Tshekardocoleidae and ?Permocupedidae), the reduction of two apical antennomeres, and the loss of the broad prothoracic postcoxal bridge (Coleoptera excluding ?Tshekardocoleidae, ?Permocupedidae and ?Rhombocoleidae). Plesiomorphic features preserved in extant Archostemata are the tuberculate cuticle, the elytral pattern with parallel longitudinal ribs and window punctures, a mesoventrite with a transverse ridge, triangular mesocoxae with a distinct meron, and the exposed metatrochantin. The fossils included in the analyses do not only contribute to the reconstruction of character evolution but also influence the branching pattern. An understanding of the major evolutionary events in Coleoptera would not be possible without considering the rich fossil record of Permian and Mesozoic beetles. © The Willi Hennig Society 2007.     

The male postabdomen of the "ancestral" archostematan beetle Tetraphalerus bruchi Heller, 1913 (Ommatidae) and its phylogenetic significance

External and internal features of the male postabdomen of Tetraphalerus bruchi were examined with a broad spectrum of morphological techniques and are described in detail. The conditions found in males of Tetraphalerus are compared to those in other archostematan beetles and members of other coleopteran suborders. The far-reaching reduction of the sternite I, structural modifications of sternite II, the retracted condition of the terminal segments, and ventromedially fused apodemes arising from the anterior margin of tergite IX are likely autapomorphies of Coleoptera. The male postabdomen of Tetraphalerus is less derived than in most other groups of Coleoptera. The sclerotized elements are symmetrical. In contrast to earlier statements on the archostematan male genital apparatus a distinctly developed, sclerotized basal piece is present. The aedeagus is trilobed and all elements of the copulatory apparatus are distinct. The muscular equipment is simple and moderately developed. All muscles (except the transverse muscles 61 and 62) occur pairwise and symmetrically. The distinct increase of the number of postabdominal muscles in representatives of the higher lineages of Coleoptera is likely linked with a torsion of the copulatory apparatus, which also results in asymmetries of the sclerotised parts. The testes of Tetraphalerus are long, multi-coiled tubes like in other archostematans, Myxophaga (Torridincola) and Adephaga. The presence of a deep notch on the parameres is a synapomorphy of Tetraphalerus and Omma. Curved parameres, a shortened distal portion, and a distinctly shortened penis are potential synapomorphies of Omma rutherfordi and Omma mastersi. The large size of the sclerotized part of the phallobase ('basal piece') and the division of the sclerotization of sternum IX are potential ground-plan autapomorphies of Archostemata, with secondary modification of the latter feature in Cupedidae. The reduced condition of the sclerotization of sternum VIII is an apomorphic condition which has likely evolved independently in Tetraphalerus and Paracupes. Further anatomical investigation of the male genital apparatus of Coleoptera and holometabolous insects in general is required for a reliable morphological and phylogenetic interpretation. Concerning the presence or absence of particular sclerotizations (e.g., 'basal piece' of phallobase) histological section series and Confocal Laser Scanning Microscopy can add more precise information to what can be observed using permanent preparations of macerated specimens.     

Complete mitochondrial genome sequence of the yellow-spotted long-horned beetle <Emphasis Type="Italic">Psacothea hilaris</Emphasis> (Coleoptera: Cerambycidae) and phylogenetic analysis among coleopteran insects

We have determined the complete mitochondrial genome of the yellow-spotted long horned beetle, Psacothea hilaris (Coleoptera: Cerambycidae), an endangered insect species in Korea. The 15,856-bp long P. hilaris mitogenome harbors gene content typical of the animal mitogenome and a gene arrangement identical to the most common type found in insect mitogenomes. As with all other sequenced coleopteran species, the 5-bp long TAGTA motif was also detected in the intergenic space sequence located between tRNA^Ser(UCN) and ND1 of P. hilaris. The 1,190-bp long non-coding A+T-rich region harbors an unusual series of seven identical repeat sequences of 57-bp in length and several stretches of sequences with the potential to form stem-and-loop structures. Furthermore, it contains one tRNA^Arg-like sequence and one tRNA^Lys-like sequence. Phylogenetic analysis among available coleopteran mitogenomes using the concatenated amino acid sequences of PCGs appear to support the sister group relationship of the suborder Polyphaga to all remaining suborders, including Adephaga, Myxophaga, and Archostemata. Among the two available infraorders in Polyphaga, a monophyletic Cucujiformia was confirmed, with the placement of Cleroidea as the basal lineage for Cucujiformia. On the other hand, the infraorder Elateriformia was not identified as monophyletic, thereby indicating that Scirtoidea and Buprestoidea are the basal lineages for Cucujiformia and the remaining Elateriformia.     

Larval morphology and phylogenetic position of Micromalthus debilis LeConte (Coleoptera: Micromalthidae)

Abstract External and internal structures of the cerambycoid and triungulin larvae of Micromalthus debilis are described and compared to features found in larvae of other groups of Coleoptera. The morphological data are evaluated with respect to the systematic position of Micromalthidae. A cladistic analysis was carried out with fifty characters. Micromalthidae are not closely related to Lymexylidae (Polyphaga: Cucujiformia) but belong to Archostemata, which is confirmed as a monophyletic unit. Micromalthidae are specialized in terms of morphology and life cycle and are characterized by a considerable number of larval autapomorphies. Their sister-group relationship with Cupedidae is supported by several apomorphic features, which are probably correlated with xylobiontic habits: head transverse and strongly rounded laterally, absence of stemmata, shortened antennae, presence of sternal asperities and presence of eversible lobes of segment IX. Cupedidae is monophyletic and Priamca is the sister group of the remaining genera of Cupedidae included in the analysis. A closer relationship between Tenomerga and Rhipsideigma is supported by several larval synapomorphies. The ancestral life style of larvae of Archostemata was probably xylobiontic. This is suggested by derived groundplan features of the suborder, which are also found in larvae of non-related, wood-associated families.     

Parthenogenesis and Polyploidy in Beetles

SYNOPSIS. Most contemporary authorities on the taxonomy of Coleopteraagree that its three-quarter million described species and subspeciesshould be placed in three suborders: Archostemata, Adephaga,and Polyphaga. Judged by the absence of males or the occurrenceof variant sex ratios, parthenogenesis occurs in all three.Those that have been studied cytologically and a tew that cansafely be surmised are discussed with reference to their probableorigin and evolutionary significance.     

Das Prothorakalskelett vonAtractocerus (Lymexylonidae) und seine Bedeutung für die Phylogenie der Coleopteren,besonders der Polyphagen (Insecta: Coleoptera)

Zusammenfassung Das Prothorakalskelett vonAtractocerus (Lymexylonidae) wird untersucht. In der sogenannten Praecoxalbrücke ist das Anepisternum durch eine als Anapleuralnaht gedeutete Furche abgeteilt. Au\erdem ist caudal ein sternaler Bereich (Basisternum und Furcasternum) abgegliedert.Die Trochantinopleura ist durch eine Naht (Pleuralnaht) in Epimeron und Katepisternum + Trochantinus unterteilt.Die Trochantinopleura samt der Coxa ist nur durch eine Membran mit dem Tergum verbunden, spezielle Gelenkstrukturen fehlen in beiden Skleriten. Die Cryptopleura ist daher weniger entwickelt als bei sonstigen Polyphagen.Ein sehr gut skierotisiertes, ausgedehntes Spinasternum ist vorhanden, au\erdem treten je zwei gro\e Postpleuralsklerite auf.Im Halsbereich findet sich au\er den Laterocervicalia jederseits ein gro\es dorsales Cervicale.Im Prothorakalbereichvon Atractocerus ist folglich eine Reihe von Strukturen erhalten und erkennbar, die bei den übrigen Coleoptera (auch bei Adephaga und Cupedidae) verschwunden sind. Die aufgefundenen VerhÄltnisse werden als sehr ursprünglich für die Polyphaga angesehen.Daher wird vermutet, da\ der ursprüngliche Prothorax der Polyphaga dem der Neuropteria sehr Ähnlich war, nÄmlich eine wenig verfestigte Pleura, die mit dem Tergum nur in lockerer Verbindung stand und distal freie und frei bewegliche Coxae besa\. Der ursprüngliche Polyphagenprothorax kommt demnach dem Grundplan des Holometabolenprothorax sehr nahe.Angesichts der Ursprünglichkeit des Polyphagenprothorax wird die Hypothese eines SchwestergruppenverhÄltnisses zwischen Coleoptera und allen übrigen Holometabola erneut zur Diskussion gestellt.Es wird die Ansicht vertreten, der Polyphagenprothorax sei gegenüber dem Prothorax der Adephaga und Cupedidae in vielen Merkmalen plesiomorph. Daher wird die Möglichkeit erwogen, da\ Cupedidae und Adephaga in einem engeren VerwandtschaftsverhÄltnis zueinander stehen als jede dieser Gruppen zu den Polyphagen.Die Stellung der Myxophaga wird diskutiert, kann jedoch zur Zeit nicht entschieden werden. Es wird die Möglichkeit erwogen, da\ die Myxophaga den Adephaga und Cupedidae verwandtschaftlich nÄher stehen als den Polyphaga, sofern die Myxophaga überhaupt eine monophyletische Einheit bilden.

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The prothoracic skeleton ofAtractocerus (Lymexylonidae) and its significance for the phylogeny of Coleoptera, especially of polyphaga (Insecta: Coleoptera)

Summary The prothoracic skeleton ofAtractocerus (Lymexylonidae) is described. In the so-called precoxal bridge the anepisternum is separated by a suture which is recognized as anapleural suture. In the caudal part of the precoxal bridge a sternal plate (basisternum and furcasternum) is separated.The trochantinopleural plate is divided by a pleural suture in epimeron and katepisternum + trochantin.The connexion of trochantinopleura and tergum is only membranous. Specialized joint structures are absent in both sclerites. The cryptopleural invagination is not as much developed as in other Polyphaga.A fairly well sclerotized and large spinasternal plate exists. Two large laterospinae are present on both sides.In the cervical region a large dorsal cervical sclerite and two lateral cervical sclerites are to be found on both sides.Some structures are recognizable in the porthoracic region ofAtractocerus which have been lost in other Coleoptera (also in Adephaga and Cupedidae). Conditions as seenm Atractocerus are believed to be very primitive among Polyphaga.Hence it is supposed, that the original prothorax of Polyphaga has been very alike the neuropterian one in possessing a pleura, membranous over lager areas, the connexion of which to the tergum was not solid. The coxae are supposed to have been free distal being able to free movement. The most primitive polyphagous prothorax is believed to come very close to the generalized prothorax of the holometabolous insects.Concerning the primitiveness of the polyphagous prothorax the hypothesis of a sister-group relation of Coleoptera and the remaining Holometabola is discussed once more.The highly plesiomorphic status of the polyphagous prothorax as compared with the prothorax of Adephaga and Cupedidae is stressed. For this reason it is considered that Cupedidae and Adephaga might be more closely related to each other, than either to the Polyphaga.The position of the Myxophaga is discussed, but is not possible to decide at present. A closer relation of the Myxophaga to Adephaga and Cupedidae than to Polyphaga is taken into consideration. It is not shure at all, however, whether the Myxophaga constitute a monophyletic group.

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Abkürzungen Aes Anepisternum - Apl Anapleuralnaht - Cpl Cryptopleura - Cx Coxa - DCv Dorsales Cervicale - Em Epimeron - Fu Furcaleinstülpung - Kes Katepisternum - LCv Laterales Cervicale - M Ansatz der Membran zwischen Pronotum und Trochantinopleura - Pl-cx Pleurocoxalgelenk - Pln Pleuralnaht - Pn Pronotum - Pps Postpleuralsklerit - Prs Praeepisternum - Sp Spinasternum - Spl Sternopleuralnaht - St Sternum - Stg Stigma - Ti Trochantinus - Ti-cx Trochantinocoxalgelenk     

Extremely miniaturised and highly complex: The thoracic morphology of the first instar larva of Mengenilla chobauti (Insecta,Strepsiptera)

Thoracic structures of the extremely small first instar larva of the strepsipteran species Mengenilla chobauti (ca. 200 μm) were examined, described and reconstructed 3-dimensionally. The focus is on the skeletomuscular system. The characters were compared to conditions found in other insect larvae of very small (Ptiliidae) or large (Dytiscus) size (both Coleoptera) and features of “triungulin” larvae, first instar larvae of Rhipiphoridae, Meloidae (both Coleoptera), and Mantispidae (Neuroptera).The specific lifestyle and the extreme degree of miniaturisation result in numerous thoracic modifications. Many sclerites of the exo- and endoskeleton are reduced. Cervical sclerites, pleural ridges, furcae and spinae are absent. Most of the longitudinal muscles are connected within the thorax, and a pair of ventral longitudinal muscles is present in the pleural region of the meso- and metathorax. This results in a high intersegmental flexibility. Due to the size reduction and the correlated shift of the brain to the thorax, with 94 identified muscles the thoracic musculature appears highly compact. Compared to larger larvae the number of both the individual muscles and the muscle bundles are distinctly reduced. The thorax of the first instar larvae displays many additional strepsipteran autapomorphies. At least partly due to the highly specialised condition, potential synapomorphies with other groups were not found.     

Permian parallelisms: Reanalysis of †Tshekardocoleidae sheds light on the earliest evolution of the Coleoptera

The Coleoptera provides an excellent example of the value of fossils for understanding the evolutionary patterns of recent lineages. We reevaluate the morphology of the Early Permian †Tshekardocoleidae to test alternative phylogenetic hypotheses relating to the Palaeozoic evolution of the order. We discuss prior interpretations and revise an earlier data matrix. Both Bayesian and parsimony analyses support the monophyly of Coleoptera excluding †Tshekardocoleidae (= Mesocoleoptera), and of Coleoptera excluding †Tshekardocoleidae and †Permocupedidae (= Metacoleoptera). Plesiomorphies preserved in †Tshekardocoleidae are elytra, which rest over the body in a loose tent-like manner, with flat lateral flanges, projecting beyond the abdominal apex, and abdomens that are flexible and nearly cylindrical. Apomorphies of Mesocoleoptera include shortening of the elytra and a closer fit with the flattened and probably more rigid abdomen. A crucial synapomorphy of Metacoleoptera is the tightly sealed subelytral space, which may have been advantageous during the Permian aridification. Taxon exclusion experiments show that †Tshekardocoleidae is crucial for understanding the early evolution of Coleoptera and that its omission strongly affects ancestral state polarities as well as topology, including crown-group taxa. By constraining the relationships of extant taxa to match those supported by phylogenomic analysis, we demonstrate that features shared by Archostemata with Permian stem groups are most reasonably supported as plesiomorphic and that the smooth and simplified body forms of Polyphaga, Adephaga, Myxophaga, and Micromalthidae were derived in parallel. Our study highlights the reciprocal illumination of molecular, morphological, and paleontological data, and paves the way for tip-dating analysis across the order.     

The beetle tree of life reveals that Coleoptera survived end‐Permian mass extinction to diversify during the Cretaceous terrestrial revolution

Here we present a phylogeny of beetles (Insecta: Coleoptera) based on DNA sequence data from eight nuclear genes, including six single‐copy nuclear protein‐coding genes, for 367 species representing 172 of 183 extant families. Our results refine existing knowledge of relationships among major groups of beetles. Strepsiptera was confirmed as sister to Coleoptera and each of the suborders of Coleoptera was recovered as monophyletic. Interrelationships among the suborders, namely Polyphaga (Adephaga (Archostemata, Myxophaga)), in our study differ from previous studies. Adephaga comprised two clades corresponding to Hydradephaga and Geadephaga. The series and superfamilies of Polyphaga were mostly monophyletic. The traditional Cucujoidea were recovered in three distantly related clades. Lymexyloidea was recovered within Tenebrionoidea. Several of the series and superfamilies of Polyphaga received moderate to maximal clade support in most analyses, for example Buprestoidea, Chrysomeloidea, Coccinelloidea, Cucujiformia, Curculionoidea, Dascilloidea, Elateroidea, Histeroidea and Hydrophiloidea. However, many of the relationships within Polyphaga lacked compatible resolution under maximum‐likelihood and Bayesian inference, and/or lacked consistently strong nodal support. Overall, we recovered slightly younger estimated divergence times than previous studies for most groups of beetles. The ordinal split between Coleoptera and Strepsiptera was estimated to have occurred in the Early Permian. Crown Coleoptera appeared in the Late Permian, and only one or two lineages survived the end‐Permian mass extinction, with stem group representatives of all four suborders appearing by the end of the Triassic. The basal split in Polyphaga was estimated to have occurred in the Triassic, with the stem groups of most series and superfamilies originating during the Triassic or Jurassic. Most extant families of beetles were estimated to have Cretaceous origins. Overall, Coleoptera experienced an increase in diversification rate compared to the rest of Neuropteroidea. Furthermore, 10 family‐level clades, all in suborder Polyphaga, were identified as having experienced significant increases in diversification rate. These include most beetle species with phytophagous habits, but also several groups not typically or primarily associated with plants. Most of these groups originated in the Cretaceous, which is also when a majority of the most species‐rich beetle families first appeared. An additional 12 clades showed evidence for significant decreases in diversification rate. These clades are species‐poor in the Modern fauna, but collectively exhibit diverse trophic habits. The apparent success of beetles, as measured by species numbers, may result from their associations with widespread and diverse substrates – especially plants, but also including fungi, wood and leaf litter – but what facilitated these associations in the first place or has allowed these associations to flourish likely varies within and between lineages. Our results provide a uniquely well‐resolved temporal and phylogenetic framework for studying patterns of innovation and diversification in Coleoptera, and a foundation for further sampling and resolution of the beetle tree of life.