Goodbye Halteria? The thoracic morphology of Endopterygota (Insecta) and its phylogenetic implications

Characters of the thorax of 30 representatives of all endopterygote orders and four hemimetabolous outgroup taxa were examined. In total, 126 characters potentially useful for phylogenetic reconstruction are discussed and presented as a data matrix. The thoracic features were analysed with different approaches combined with an additional large set of morphological data. Endopterygota were confirmed as monophyletic and new morphological autapomorphies of the group are suggested. The highly controversial Strepsiptera are not placed as sistergroup of Diptera (Halteria‐concept) but consistently as sistergroup of Coleoptera. This clade was mainly supported by characters associated with posteromotorism. The traditionally proposed relationship of Neuropterida + Coleoptera was not confirmed. Hymenoptera was placed as sistergroup of all remaining orders in parsimony analyses. The inclusion of Strepsiptera + Coleoptera in Mecopterida in parsimony analyses is probably artificial and potential thoracic autapomorphies of Mecopterida in the traditional sense are suggested. Mecopterida are confirmed as a clade in Bayesian analyses. Amphiesmenoptera and Antliophora are well supported. The paraphyly of Mecoptera is due to a clade comprising Nannochoristidae and Siphonaptera + Diptera. The phylogenetic reconstruction using characters of the thorax is impeded by functional constraints, parallel losses, a general trend to reinforce the skeleton and to simplify the muscular apparatus, and also by different specializations occurring in potential outgroup taxa. The addition of a large additional morphological data set only partly compensated for these problems. It is apparent that the inclusion of more outgroup and ingroup taxa is required, notably presumably basal representatives of Mecoptera, Trichoptera, and Diptera. This may reduce the effect of an artificial attraction of branches caused by homoplasy, notably character losses occurring within different lineages.© The Willi Hennig Society 2010.     

Phylogenetic relationships among insect orders based on three nuclear protein-coding gene sequences

Many attempts to resolve the phylogenetic relationships of higher groups of insects have been made based on both morphological and molecular evidence; nonetheless, most of the interordinal relationships of insects remain unclear or are controversial. As a new approach, in this study we sequenced three nuclear genes encoding the catalytic subunit of DNA polymerase delta and the two largest subunits of RNA polymerase II from all insect orders. The predicted amino acid sequences (In total, approx. 3500 amino acid sites) of these proteins were subjected to phylogenetic analyses based on the maximum likelihood and Bayesian analysis methods with various models. The resulting trees strongly support the monophyly of Palaeoptera, Neoptera, Polyneoptera, and Holometabola, while within Polyneoptera, the groupings of Isoptera/"Blattaria"/Mantodea (Superorder Dictyoptera), Dictyoptera/Zoraptera, Dermaptera/Plecoptera, Mantophasmatodea/Grylloblattodea, and Embioptera/Phasmatodea are supported. Although Paraneoptera is not supported as a monophyletic group, the grouping of Phthiraptera/Psocoptera is robustly supported. The interordinal relationships within Holometabola are well resolved and strongly supported that the order Hymenoptera is the sister lineage to all other holometabolous insects. The other orders of Holometabola are separated into two large groups, and the interordinal relationships of each group are (((Siphonaptera, Mecoptera), Diptera), (Trichoptera, Lepidoptera)) and ((Coleoptera, Strepsiptera), (Neuroptera, Raphidioptera, Megaloptera)). The sister relationship between Strepsiptera and Diptera are significantly rejected by all the statistical tests (AU, KH and wSH), while the affinity between Hymenoptera and Mecopterida are significantly rejected only by AU and KH tests. Our results show that the use of amino acid sequences of these three nuclear genes is an effective approach for resolving the relationships of higher groups of insects.     

The Strepsiptera problem: phylogeny of the holometabolous insect orders inferred from 18S and 28S ribosomal DNA sequences and morphology

Phylogenetic relationships among the holometabolous insect orders were inferred from cladistic analysis of nucleotide sequences of 18S ribosomal DNA (rDNA) (85 exemplars) and 28S rDNA (52 exemplars) and morphological characters. Exemplar outgroup taxa were Collembola (1 sequence), Archaeognatha (1), Ephemerida (1), Odonata (2), Plecoptera (2), Blattodea (1), Mantodea (1), Dermaptera (1), Orthoptera (1), Phasmatodea (1), Embioptera (1), Psocoptera (1), Phthiraptera (1), Hemiptera (4), and Thysanoptera (1). Exemplar ingroup taxa were Coleoptera: Archostemata (1), Adephaga (2), and Polyphaga (7); Megaloptera (1); Raphidioptera (1); Neuroptera (sensu stricto = Planipennia): Mantispoidea (2), Hemerobioidea (2), and Myrmeleontoidea (2); Hymenoptera: Symphyta (4) and Apocrita (19); Trichoptera: Hydropsychoidea (1) and Limnephiloidea (2); Lepidoptera: Ditrysia (3); Siphonaptera: Pulicoidea (1) and Ceratophylloidea (2); Mecoptera: Meropeidae (1), Boreidae (1), Panorpidae (1), and Bittacidae (2); Diptera: Nematocera (1), Brachycera (2), and Cyclorrhapha (1); and Strepsiptera: Corioxenidae (1), Myrmecolacidae (1), Elenchidae (1), and Stylopidae (3). We analyzed approximately 1 kilobase of 18S rDNA, starting 398 nucleotides downstream of the 5' end, and approximately 400 bp of 28S rDNA in expansion segment D3. Multiple alignment of the 18S and 28S sequences resulted in 1,116 nucleotide positions with 24 insert regions and 398 positions with 14 insert regions, respectively. All Strepsiptera and Neuroptera have large insert regions in 18S and 28S. The secondary structure of 18S insert 23 is composed of long stems that are GC rich in the basal Strepsiptera and AT rich in the more derived Strepsiptera. A matrix of 176 morphological characters was analyzed for holometabolous orders. Incongruence length difference tests indicate that the 28S + morphological data sets are incongruent but that 28S + 18S, 18S + morphology, and 28S + 18S + morphology fail to reject the hypothesis of congruence. Phylogenetic trees were generated by parsimony analysis, and clade robustness was evaluated by branch length, Bremer support, percentage of extra steps required to force paraphyly, and sensitivity analysis using the following parameters: gap weights, morphological character weights, methods of data set combination, removal of key taxa, and alignment region. The following are monophyletic under most or all combinations of parameter values: Holometabola, Polyphaga, Megaloptera + Raphidioptera, Neuroptera, Hymenoptera, Trichoptera, Lepidoptera, Amphiesmenoptera (Trichoptera + Lepidoptera), Siphonaptera, Siphonaptera + Mecoptera, Strepsiptera, Diptera, and Strepsiptera + Diptera (Halteria). Antliophora (Mecoptera + Diptera + Siphonaptera + Strepsiptera), Mecopterida (Antliophora + Amphiesmenoptera), and Hymenoptera + Mecopterida are supported in the majority of total evidence analyses. Mecoptera may be paraphyletic because Boreus is often placed as sister group to the fleas; hence, Siphonaptera may be subordinate within Mecoptera. The 18S sequences for Priacma (Coleoptera: Archostemata), Colpocaccus (Coleoptera: Adephaga), Agulla (Raphidioptera), and Corydalus (Megaloptera) are nearly identical, and Neuropterida are monophyletic only when those two beetle sequences are removed from the analysis. Coleoptera are therefore paraphyletic under almost all combinations of parameter values. Halteria and Amphiesmenoptera have high Bremer support values and long branch lengths. The data do not support placement of Strepsiptera outside of Holometabola nor as sister group to Coleoptera. We reject the notion that the monophyly of Halteria is due to long branch attraction because Strepsiptera and Diptera do not have the longest branches and there is phylogenetic congruence between molecules, across the entire parameter space, and between morphological and molecular data.     

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.     

The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid‐Cretaceous

Many extant insects have developed pad structures, euplantulae or arolia on their tarsi to increase friction or enhance adhesion for better mobility. Many polyneopteran insects with euplantulae, for example, Grylloblattodea, Mantophasmatodea and Orthoptera, have been described from the Mesozoic. However, the origin and evolution of stick insects' euplantulae are poorly understood due to rare fossil records. Here, we report the earliest fossil records of Timematodea hitherto, Tumefactipes prolongates gen. et sp. nov. and Granosicorpes Urates gen. et sp. nov., based on three specimens from mid-Cretaceous Burmese amber. Specimens of Tumefactipes prolongates gen. et sp. nov. have extremely specialized and expanded euplantulae on their tarsomere II. These new findings are the first known and the earliest fossil records about euplantula structure within Phasmatodea, demonstrating the diversity of euplantulae in Polyneoptera during the Mesozoic. Such tarsal pads might have increased friction and helped these mid-Cretaceous stick insects to climb more firmly on various surfaces, such as broad leaves, wetted tree branches or ground. These specimens provide more morphological data for us to understand the relationships of Timematodea, Euphasmatodea, Orthoptera and Embioptera, suggesting that Timematodea might be monophyletic with Euphasmatodea rather than Embioptera and Phasmatodea should have a closer relationship with Orthoptera rather than Embioptera.     

Monophyletic Polyneoptera recovered by wing base structure

Phylogenetic relationships among the winged orders of Polyneoptera [Blattodea, Dermaptera, Embiodea (=Embioptera), Isoptera, Mantodea, Orthoptera, Phasmatodea, Plecoptera and Zoraptera] were estimated based on morphological data selected from the hindwing base structure. Cladistic analyses were carried out using hindwing base data alone and in combination with other, more general, morphological data. Both datasets resulted in similar trees and recovered the monophyly of Polyneoptera. Deepest phylogenetic relationships among the polyneopteran orders were not confidently estimated, but the monophyly of Mystroptera (= Embiodea + Zoraptera), Orthopterida (= Orthoptera + Phasmatodea) and Dictyoptera (= Blattodea + Mantodea + Isoptera) was supported consistently. In contrast, placements of Plecoptera and Dermaptera were unstable, although independent analysis of the wing base data supported their sister‐group relationship with two nonhomoplasious synapomorphies (unique conditions in the ventral basisubcostale, and in the articulation between the antemedian notal wing process and first axillary sclerite). Results from the combined wing base plus general morphology data were consistent, even if the wingless orders Grylloblattodea and Mantophasmatodea were included in the analysis. Generally, trees obtained from the present analyses were concordant with the results from other morphological and molecular analyses, but Isoptera were placed inappropriately to be the sister of Blattodea + Mantodea by the inclusion of the wing base data, probably as a result of morphological regressions of the order.     

Evolution of locomotory attachment pads in the Dermaptera (Insecta)

This contribution is the first comparative SEM study of tarsal and pretarsal structures of 18 dermapteran species, including epizoic Hemimeridae, rare Apachyidae, as well as basal Pygidicranidae. Our data reject the apparent uniformity of this taxon and show that representatives of Dermaptera have independently evolved both types of attachment mechanisms: hairy and smooth. Dermaptera possess a wide spectrum of attachment devices: arolia, euplantulae, tarsal surfaces covered with specialised tenent setae and other types of cuticular outgrowths. The groundpattern of the pretarsal and tarsal attachment structures was reconstructed by mapping their characters onto a cladogram, generated without tarsal characters. In the groundpattern of recent Dermaptera, the tarsus consists of three tarsomeres. Presumably, the last common ancestor of the Dermaptera possessed an arolium, since this structure occurs in the most basal taxa: Diplatyidae, Karschiellidae (partim, adults), Pygidicranidae partim, and Apachyidae. The absence of arolium in two of the pygidicranid taxa is probably due to a secondary loss. The arolium seems to be reduced in the 'higher Dermaptera' and amongst them, only the Geracinae, which belong to the Spongiphoridae and, hence, to the well supported Eudermaptera [European Journal of Entomology, 98 (2001), 445], evolved this structure convergently. The character state distribution for euplantulae suggests their evolution being similar to that of the arolium. All species of Tagalina possess a specialised tarsus with a strongly dilated second tarsomere. The same applies to the Forficulidae. However, their relatively remote phylogenetic position to Tagalina burri is a convincing reason to assume convergent evolution of this character. The Chelisochidae, with a slender, elongated second tarsomere, possess a unique structure, which supports their monophyly. The special, heart shaped structure of the second tarsal segments in the Forficulidae suggests their monophyly. The attachment structures of Hemimerus vosseleri are highly derived and probably autapomorphic for this taxon.     

Relationships among the major lineages of Dictyoptera: the effect of outgroup selection on dictyopteran tree topology

Abstract Dictyoptera, comprising Blattaria, Isoptera, and Mantodea, are diverse in appearance and life history, and are strongly supported as monophyletic. We downloaded COII, 16S, 18S, and 28S sequences of 39 dictyopteran species from GenBank. Ribosomal RNA sequences were aligned manually with reference to secondary structure. We included morphological data (maximum of 175 characters) for 12 of these taxa and for an additional 15 dictyopteran taxa (for which we had only morphological data). We had two datasets, a 59‐taxon dataset with five outgroup taxa, from Phasmatodea (2 taxa), Mantophasmatodea (1 taxon), Embioptera (1 taxon), and Grylloblattodea (1 taxon), and a 62‐taxon dataset with three additional outgroup taxa from Plecoptera (1 taxon), Dermaptera (1 taxon) and Orthoptera (1 taxon). We analysed the combined molecular?morphological dataset using the doublet and MK models in Mr Bayes , and using a parsimony heuristic search in paup . Within the monophyletic Mantodea, Mantoida is recovered as sister to the rest of Mantodea, followed by Chaeteessa; the monophyly of most of the more derived families as defined currently is not supported. We recovered novel phylogenetic hypotheses about the taxa within Blattodea (following Hennig, containing Isoptera). Unique to our study, one Bayesian analysis places Polyphagoidea as sister to all other Dictyoptera; other analyses and/or the addition of certain orthopteran sequences, however, place Polyphagoidea more deeply within Dictyoptera. Isoptera falls within the cockroaches, sister to the genus Cryptocercus. Separate parsimony analyses of independent gene fragments suggest that gene selection is an important factor in tree reconstruction. When we varied the ingroup taxa and/or outgroup taxa, the internal dictyopteran relationships differed in the position of several taxa of interest, including Cryptocercus, Polyphaga, Periplaneta and Supella. This provides further evidence that the choice of both outgroup and ingroup taxa greatly affects tree topology.