Thomas Hörnschemeyer

Morphological and molecular evidence converge upon a robust phylogeny of the megadiverse Holometabola

We present the largest morphological character set ever compiled for Holometabola. This was made possible through an optimized acquisition of data. Based on our analyses and recently published hypotheses based on molecular data, we discuss higher‐level phylogeny and evolutionary changes. We comment on the information content of different character systems and discuss the role of morphology in the age of phylogenomics. Microcomputer tomography in combination with other techniques proved highly efficient for acquiring and documenting morphological data. Detailed anatomical information (356 characters) is now available for 30 representatives of all holometabolan orders. A combination of traditional and novel techniques complemented each other and rapidly provided reliable data. In addition, our approach facilitates documenting the anatomy of model organisms. Our results show little congruence with studies based on rRNA, but confirm most clades retrieved in a recent study based on nuclear genes: Holometabola excluding Hymenoptera, Coleopterida (= Strepsiptera + Coleoptera), Neuropterida excl. Neuroptera, and Mecoptera. Mecopterida (= Antliophora + Amphiesmenoptera) was retrieved only in Bayesian analyses. All orders except Megaloptera are monophyletic. Problems in the analyses are caused by taxa with numerous autapomorphies and/or inapplicable character states due to the loss of major structures (such as wings). Different factors have contributed to the evolutionary success of various holometabolan lineages. It is likely that good flying performance, the ability to occupy different habitats as larvae and adults, parasitism, liquid feeding, and co‐evolution with flowering plants have played important roles. We argue that even in the “age of phylogenomics”, comparative morphology will still play a vital role. In addition, morphology is essential for reconstructing major evolutionary transformations at the phenotypic level, for testing evolutionary scenarios, and for placing fossil taxa.
© The Willi Hennig Society 2010.

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.

Insect morphology in the age of phylogenomics: innovative techniques and its future role in systematics

A brief account of the history of insect morphology is given. Different techniques and analytical methods used in current projects on insect morphology and phylogeny and their optimized combined application are described. These include fixation, dissection, maceration, histology (microtome sectioning), scanning electron microscopy (SEM), transmission electron microscopy (TEM), serial block‐face scanning electron microscopy (SBFSEM), focused ion beam scanning electron microscopy (FIB/SEM), confocal laser scanning microscopy (CLSM), bleaching, micro‐computed tomography (μCT), computer‐based three‐dimensional reconstruction, focus stacking of digital images, geometric morphometrics and the storage of morphological metadata. The role of insect morphology in the “age of phylogenomics” is discussed.

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.

Investigation of insect morphology by MRI: assessment of spatial and temporal resolution

Classically, the investigation of the internal morphology of insects relies on histologic methods, e.g., the preparation of thin tissue sections. However, the preparation of serial sections is time consuming and means the irreversible loss of the animal. In the present investigation, we have analyzed the potential of NMR imaging as a tool for the morphologic classification of insects with sufficient spatial resolution. With a 512 matrix, 15 mm FOV, 200 microm slice thickness, images with an in-plane spatial resolution of 30 microm are obtained with a signal-to-noise ratio of 70. These conditions require only seven averages, resulting in an experimental time of only 50 min. Such image quality already permits the differentiation of fine structural and morphologic details such as e.g., intestinal tracts and copulation organ in a beetle. Also, wing controlling dorsal muscle groups as well as leg structures and joints are clearly distinguishable. We conclude that the spatial resolution and contrast condition of MR imaging are quite promising for the new approach of zoological insect classification using NMR imaging. Further principally available technical enhancement of sensitivity and spatial resolution will provide an attractive alternative to invasive techniques for the classification of, sometimes, rare and precious insect specimen.

The thorax of Mantophasmatodea, the morphology of flightlessness, and the evolution of the neopteran insects

Mantophasmatodea was described as a new insect order in 2002. Since then, this small group of wingless insects has developed into one of the best investigated insect taxa. Nevertheless, many aspects of mantophasmatodean morphology as well as their evolutionary relationships remain ambiguous. To determine the phylogenetic relationships of Mantophasmatodea based on an extended character set and to elucidate possible morphological adaptions towards flightlessness, we investigated the thoracic morphology of two species, Austrophasma caledonensis and Mantophasma sp. The morphological similarity between these two species is striking and no differences in musculature were found. The mantophasmatodean thorax strongly resembles that of ice crawlers (Grylloblattodea), especially with respect to the presence of pleural processes in the meso‐ and metathorax, branched furcae in all segments, and similar muscle equipment. In a cladistic analysis containing all major lineages of Neoptera, the monophyly of Polyneoptera is supported by the presence of an anal fan and several modifications of the wing joint. Within Polyneoptera, a sister‐group relationship between stoneflies and the remaining Polyneoptera is supported. A clade comprising Mantophasmatodea and the Grylloblattodea gains strong support from thoracic morphology and can be considered assured. Potential thoracic apomorphies include prothoracic paracoxal invaginations, pterothoracic pleural arms that originate from the epimeron, and a unique metathoracic sterno‐coxal musculature. The monophyly of Orthoptera and Dictyoptera is further supported while the deeper polyneopteran nodes remain unresolved. Among the wingless taxa investigated we found few general morphological adaptations whereas, in other aspects, especially in the musculature, strong differences could be observed. However, much more research on the strongly neglected topic of flightlessness is required to make reliable statements.

Late Palaeozoic Paoliida is the sister group of Dictyoptera (Insecta: Neoptera)

Paoliida is an insect group of highly controversial composition and equally controversial affinities. Based on comprehensive reinvestigations we propose a new delimitation of the insect order Paoliida sensu nov. associating the families Paoliidae and Blattinopsidae on the basis of the following main wing venation characters: veins CuA convex and CuP concave separating from a rather long basal stem Cu; a short, more or less distinct, but generally convex arculus brace (crossvein) between M and CuA (more distinct in forewing than in hind wing), and a broad area containing veinlets, between CuP and CuA, with a general course of CuA making a double curve (autapomorphy); CuP straight or sigmoidal. The Paoliida is considered as a neopteran clade and potential sister group of the Dictyoptera on the basis of the presence of well-defined anterior branches of CuA, with the same convexity as the median vein and more concave than the posterior branches of the same vein (synapomorphy). The polarities of the other characters shared by these clades are discussed. New diagnoses of the order Paoliida and the family Paoliidae are provided after re-examination of the type material. We attribute Herbstiala herbsti to Paoliidae and consider Herbstialidae as a junior synonym of this family. The grylloblattid family Ideliidae is considered as a junior synonym of Paoliidae, transferring genera Stenaropodites, Aenigmidelia, Archidelia, Sojanidelia, Micaidelia, Acropermula and Mongoloidelia to this family. Kochopteron hoffmannorum and Protoblattina bouvieri are newly included in Paoliidae. Protoblattinopsis stubblefieldi is reinterpreted as a hind wing having highly specialized cubito-anal structures functionally analogous to the anal loop structure of the hind wing of the Mesozoic Isophlebioidea (Odonatoptera). We attribute Protoblattinopsis to Paoliida and consider Protoblattinidae as a junior synonym of Paoliidae. Furthermore, a new Paoliidae, Silesiapteron jarmilae gen. et sp. nov. is described from Upper Carboniferous sphaerosiderite concretion of Poland. http://zoobank.org/urn:lsid:zoobank.org:pub:296A17BD-2A84-4C1F-B19E-737DDFE7E17C

The species-level phylogeny of archostematan beetles - where do Micromalthus debilis and Crowsoniella relicta belong?

A species‐level phylogenetic analysis comprising 37 of the 45 known extant species of archostematan beetles and a total of 110 morphological characters from adults and larvae is presented. For the first time, characters of the male genitalia are included in a phylogenetic analysis of Archostemata. The dataset is analysed with parsimony as well as with Bayesian algorithms. Analyses with differently arranged datasets, with larval characters included or excluded, and including or excluding Micromalthus debilis and Crowsoniella relicta are conducted. The resulting hypothesis of the species‐level phylogeny of Archostemata confirms Cupedidae and Ommatidae as monophyletic taxa. Within Cupedidae, the South American Paracupes and the North American Priacma together are the sister group to all remaining Cupedidae. Among the latter, the identification of a clade comprising Rhipsideigma, Cupes capitatus and Tenomerga leucophaea renders Tenomerga polyphyletic. Ascioplaga scalenacomb. nov. is transferred from Adinolepis. Characters of the male genitalia support phylogenetic affinities of Micromalthus debilis with Ommatidae and of Crowsoniella relicta with Cupedidae.

The thorax musculature of Anisoptera ( Insecta: Odonata) nymphs and its evolutionary relevance

BackgroundAmong the winged insects (Pterygota) the Odonata (dragon- and damselflies) are special for several reasons. They are strictly aerial predators showing remarkable flight abilities and their thorax morphology differs significantly from that of other Pterygota in terms of the arrangement and number of muscles. Even within one individual the musculature is significantly different between the nymphal and adult stage.ResultsHere we present a comparative morphological investigation of the thoracic musculature of dragonfly (Anisoptera) nymphs. We investigated representatives of the Libellulidae, Aeshnidae and Cordulegasteridae and found 71 muscles: 19 muscles in the prothorax, 26 in the mesothorax and 27 in the metathorax. Nine of these muscles were previously unknown in Odonata, and for seven muscles no homologous muscles could be identified in the neopteran thorax.ConclusionOur results support and extend the homology hypotheses for the thoracic musculatures of Odonata and Neoptera, thus supplementing our understanding of the evolution of Pterygota and providing additional characters for phylogenetic analyses comprising all subgroups of Pterygota.

Serial block-face imaging and its potential for reconstructing diminutive cell systems: a case study from arthropods.

Until recently, three-dimensional reconstruction on an ultrastructural level was only possible using serial section transmission electron microscopy (ssTEM). However, ssTEM is highly challenging and prone to artifacts as, e.g., section loss and image distortions. New methods, such as serial block-face scanning electron microscopy (SBFSEM) overcome these limitations and promise a high lateral resolution. However, little is known about the usability of SBFSEM in diminutive, but highly complex cellular systems. We used spider sperm (~3 µm in diameter), which fulfills these conditions, to analyze the potential of SBFSEM compared with ssTEM. Our data suggest that the resolution obtained by SBFSEM allows depicting structures on a cellular level and is sufficient to discriminate subcellular components, but is highly dependent on previous staining procedures and electron density of the target structures.