A molecular phylogeny of Hemiptera inferred from mitochondrial genome sequences

Inconsistencies in the Classification of the Family Cydnidae (Hemiptera: Heteroptera: Pentatomoidea) Revealed by Molecular Apomorphies in the Secondary and Tertiary Structures of 18S rRNA Length-Variable Region L (LVR L)

The SSU nuclear rDNA (encoding 18S ribosomal RNA) is one of the most frequently sequenced genes in the molecular analysis of insects. Molecular apomorphies in the secondary and tertiary structures of several 18S rRNA length-variable regions (LVRs) located within the V2, V4, and V7 hypervariable regions can be good indicators for recovering monophyletic groups within some heteropteran families. Among the LVRs that have been analysed, the LVR L in the V4 hypervariable region is the longest and most crucial for such assessments. We analysed the 18S rRNA V4 hypervariable region sequences of 45 species from the family Cydnidae, including all 6 subfamilies (Amaurocorinae, Amnestinae, Cephalocteinae, Cydninae, Garsauriinae, and Sehirinae) and three pentatomoid families (Parastrachiidae, Thaumastellidae, and Thyreocoridae), which have often been included in the broadly defined Cydnidae family. This is the first time that representatives of all Cydnidae subfamilies have been included in a molecular analysis. Only taxa from two subfamilies, Sehirinae and Cydninae, have been used in previous molecular studies. The secondary and tertiary structures of the LVR L were predicted for each species using the two-step procedure already accepted for such analyses to recover any molecular apomorphy essential for determining monophyly. The results of our comparative studies contradict the current understanding of the relationships among burrowing bugs and the current family classification.

Comparative study of neuropeptide signaling systems in Hemiptera

Numerous physiological processes in insects are tightly regulated by neuropeptides and their receptors. Although they form an ancient signaling system, there is still a great deal of variety in neuropeptides and their receptors among different species within the same order. Neuropeptides and their receptors have been documented in many hemipteran insects, but the differences among them have been poorly characterized. Commercial grapevines worldwide are plagued by the bug Daktulosphaira vitifoliae (Hemiptera: Sternorrhyncha). Here, 33 neuropeptide precursors and 48 putative neuropeptide G protein-coupled receptor (GPCR) genes were identified in D. vitifoliae. Their expression profiles at the probe and feeding stages reflected potential regulatory roles in probe behavior. By comparison, we found that the Releasing Hormone-Related Peptides (GnRHs) system of Sternorrhyncha was differentiated from those of the other 2 suborders in Hemiptera. Independent secondary losses of the adipokinetic hormone/corazonin-related peptide receptor (ACP) and corazonin (CRZ) occurred during the evolution of Sternorrhyncha. Additionally, we discovered that the neuropeptide signaling systems of Sternorrhyncha were very different from those of Heteroptera and Auchenorrhyncha, which was consistent with Sternorrhyncha's phylogenetic position at the base of the order. This research provides more knowledge on neuropeptide systems and sets the groundwork for the creation of novel D. vitifoliae management strategies that specifically target these signaling pathways.

Reduction of embryonic E93 expression as a hypothetical driver of the evolution of insect metamorphosis

The early embryo of the cockroach Blattella germanica exhibits high E93 expression. In general, E93 triggers adult morphogenesis during postembryonic development. Here we show that E93 is also crucial in early embryogenesis in the cockroach, as a significant number of E93-depleted embryos are unable to develop the germ band under maternal RNAi treatment targeting E93. Moreover, transcriptomic analysis indicates that E93 depletion results in important gene expression changes in the early embryo, and many of the differentially expressed genes are involved in development. Then, using public databases, we gathered E93 expression data in embryo and preadult stages, finding that embryonic expression of E93 is high in hemimetabolan species (whose juveniles, or nymphs, are similar to the adult) and low in holometabolans (whose juveniles, or larvae, are different from the adult). E93 expression is also low in Thysanoptera and in Hemiptera Sternorrhyncha, hemimetabolans with postembryonic quiescent stages, as well as in Odonata, the nymph of which is very different from the adult. In ametabolans, such as the Zygentoma Thermobia domestica, E93 transcript levels are very high in the early embryo, whereas during postembryonic development they are medium and relatively constant. We propose the hypothesis that during evolution, a reduction of E93 expression in the embryo of hemimetabolans facilitated the larval development and the emergence of holometaboly. Independent decreases of E93 transcripts in the embryo of Odonata, Thysanoptera, and different groups of Hemiptera Sternorrhyncha would have allowed the development of modified juvenile stages adapted to specific ecophysiological conditions.

Characterizing the Complete Mitochondrial Genomes of Three Bugs (Hemiptera: Heteroptera) Harming Bamboo

Herein, we report the mitochondrial genomic characteristics of three insect pests, Notobitus meleagris, Macropes harringtonae, and Homoeocerus bipunctatus, collected from bamboo plants in Guizhou Province, China. For the first time, the damaged conditions and life histories of M. harringtonae and H. bipunctatus are described in detail and digital photographs of all their life stages are provided. Simultaneously, the mitochondrial genome sequences of three bamboo pests were sequenced and analyzed. Idiocerus laurifoliae and Nilaparvata lugens were used as outgroups, and the phylogenetic trees were constructed. The mitochondrial genomes of the three bamboo pests contained 37 classical genes, including 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNAs (tRNAs), and a control region, with a total length of 16,199 bp, 15,314 bp, and 16,706 bp, respectively. The A+T values of the three bamboo pests were similar, and trnS1 was a cloverleaf structure with missing arms. The phylogenetic analyses, using the Bayesian inference (BI) and Maximum likelihood (ML), supported that N. meleagris and H. bipunctatus belonged to the Coreoidea family, whereas M. harringtonae belonged to the Lygaeoidea family with high support values. This study involves the first complete sequencing of the mitochondrial genomes of two bamboo pests. By adding these newly sequenced mitochondrial genome data and detailed descriptions of life histories, the database of bamboo pests is improved. These data also provide information for the development of bamboo pest control methods by quick identification techniques and the use of detailed photographs.

Description of mitochon genome and phylogenetic considerations of Sabethes bipartipes, Sabethes cyaneus, Sabethes quasicyaneus, and Sabethes tarsopus (Diptera: Culicidae)

The genus Sabethes (Diptera: Culicidae) comprises species of great epidemiological relevance, particularly involved in transmission cycles of the Yellow fever virus in South America. Given the unavailability of information related to aspects of evolutionary biology and molecular taxonomy of species of this genus of mosquitoes, we report here the first sequencing of the mitochondrial genomes of Sabethes bipartipes, Sabethes cyaneus, Sabethes tarsopus, and Sabethes quasicyaneus. The sequences obtained showed an average length of 14,920 bp, comprising 37 functional genes (13 PCGs, 22 tRNA, and 02 rRNA). The phylogenies reconstructed by Maximum likelihood and Bayesian inference methods, based on the concatenated sequences of all 13 PCGs, produced similar topologies and strongly supported the monophyletic relationship between the Sabethes subgenera, corroborating the known taxonomic classification based on aspects of the external morphology of the taxa assessed. The data and information produced from the Sabethes species evaluated here may be useful for future taxonomic and evolutionary studies of the genus, as well as the Culicidae family.

A complex interplay of evolutionary forces continues to shape ancient co-occurring symbiont genomes

Many insects depend on ancient associations with intracellular bacteria for essential nutrition. The genomes of these bacteria are often highly reduced. Although drift is a major driver of symbiont evolution, other evolutionary forces continue to influence them. To understand how ongoing molecular evolution and gene loss shape symbiont genomes, we sequenced two of the most ancient symbionts known, Sulcia and Nasuia, from 20 Hawaiian Nesophrosyne leafhoppers. We leveraged the parallel divergence of Nesophrosyne lineages throughout Hawaii as a natural experimental framework. Sulcia and Nasuia experience ongoing-but divergent-gene loss, often in a convergent fashion. Although some genes are under relaxed selection, purifying and positive selection are also important drivers of genome evolution, particularly in maintaining certain nutritional and cellular functions. Our results further demonstrate that symbionts experience dramatically different evolutionary environments, as evidenced by the finding that Sulcia and Nasuia have one of the slowest and fastest rates of molecular evolution known.

Comparative Analysis of the Complete Mitochondrial Genomes of Five Species of Ricaniidae (Hemiptera: Fulgoromorpha) and Phylogenetic Implications

Ricaniidae is a relatively small planthopper family with about 69 genera and 442 species worldwide. Members of this family occur throughout the warm temperate and tropical regions. Some species cause devastating damage to major agricultural and economic plants. However, the relationship between Ricaniidae and other families of Fulgoroidea needs to be further explored. The morphological definitions of the two biggest genera, Pochazia Amyot & Serville, 1843 and Ricania Germar, 1818 (the type genus of Ricaniidae) remain controversial. In this study, mitogenomes of five representatives in these two genera were decoded using the next-generation sequence method and genome assembly. Results showed that their complete mitogenomes are circular DNA molecules with 15,457 to 16,411 bp. All protein-coding genes (PCGs) begin with the start codon ATN, GTG or TTG and end with TAA, TAG, an incomplete stop codon single T or an incomplete stop codon single A. A lost DHU arm was discovered in the trnS gene of the five mitogenomes and the trnV gene within Pochaziaconfusa, Pochazia guttifera and Ricania simulans. The remnant tRNAs folded into clover-leaf structures. The sliding window, genetic distance, and Ka/Ks analyses indicated that the cox1 gene is the slowest evolving and is relatively conserved. The phylogenetic tree topologies support (Delphacidae + (((Issidae + (Lophopidae + Caliscelidae)) + (Flatidae + Ricaniidae)) + (Achilidae + (Dictyopharidae + Fulgoridae)))) as the best topology, as recognized by both PhyloBayes, RAxML and MrBayes based on four data sets (PCG, PCGRNA, PCG12, PCG12RNA). The monophyly of Ricaniidae and the sister group status of two families Flatidae and Ricaniidae are supported, but all analyses failed to support the monophyly of Pochazia and Ricania. The diagnoses between these two genera cannot be resolved until more evidence is acquired.

First Description of the Mitogenome and Phylogeny of Culicinae Species from the Amazon Region

The Culicidae family is distributed worldwide and comprises about 3587 species subdivided into the subfamilies Anophelinae and Culicinae. This is the first description of complete mitochondrial DNA sequences from Aedes fluviatilis, Aedeomyia squamipennis, Coquillettidia nigricans, Psorophora albipes, and Psorophora ferox. The mitogenomes showed an average length of 15,046 pb and 78.02% AT content, comprising 37 functional subunits (13 protein coding genes, 22 tRNAs, and two rRNAs). The most common start codons were ATT/ATG, and TAA was the stop codon for all PCGs. The tRNAs had the typical leaf clover structure, except tRNA^Ser1. Phylogeny was inferred by analyzing the 13 PCGs concatenated nucleotide sequences of 48 mitogenomes. Maximum likelihood and Bayesian inference analysis placed Ps. albipes and Ps. ferox in the Janthinosoma group, like the accepted classification of Psorophora genus. Ae. fluviatilis was placed in the Aedini tribe, but was revealed to be more related to the Haemagogus genus, a result that may have been hampered by the poor sampling of Aedes sequences. Cq. nigricans clustered with Cq. chrysonotum, both related to Mansonia. Ae. squamipennis was placed as the most external lineage of the Culicinae subfamily. The yielded topology supports the concept of monophyly of all groups and ratifies the current taxonomic classification.

Characterization of the complete mitochondrial genome of Myrmuslateralis (Heteroptera, Rhopalidae) and its implication for phylogenetic analyses

Mitochondrial genomes (mitogenomes) are widely used in research studies on phylogenetic relationships and evolutionary history. Here, we sequenced and analyzed the mitogenome of the scentless plant bug Myrmuslateralis Hsiao, 1964 (Heteroptera, Rhopalidae). The complete 17,309 bp genome encoded 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a control region. The mitogenome revealed a high A+T content (75.8%), a positive AT-skew (0.092), and a negative GC-skew (-0.165). All 13 PCGs were found to start with ATN codons, except for cox1, in which TTG was the start codon. The Ka/Ks ratios of 13 PCGs were all lower than 1, indicating that purifying selection evolved in these genes. All tRNAs could be folded into the typical cloverleaf secondary structure, except for trnS1 and trnV, which lack dihydrouridine arms. Phylogenetic trees were constructed and analyzed based on the PCG+rRNA from 38 mitogenomes, using maximum likelihood and Bayesian inference methods, showed that M.lateralis and Chorosomamacilentum Stål, 1858 grouped together in the tribe Chorosomatini. In addition, Coreoidea and Pyrrhocoroidea were sister groups among the superfamilies of Trichophora, and Rhopalidae was a sister group to Alydidae + Coreidae.

Complete Mitochondrial Genomes of Metcalfa pruinosa and Salurnis marginella (Hemiptera: Flatidae): Genomic Comparison and Phylogenetic Inference in Fulgoroidea

The complete mitochondrial genomes (mitogenomes) of two DNA barcode-defined haplotypes of Metcalfa pruinosa and one of Salurnis marginella (Hemiptera: Flatidae) were sequenced and compared to those of other Fulgoroidea species. Furthermore, the mitogenome sequences were used to reconstruct phylogenetic relationships among fulgoroid families. The three mitogenomes, including that of the available species of Flatidae, commonly possessed distinctive structures in the 1702-1836 bp A+T-rich region, such as two repeat regions at each end and a large centered nonrepeat region. All members of the superfamily Fulgoroidea, including the Flatidae, consistently possessed a motiflike sequence (TAGTA) at the ND1 and trnS₂ junction. The phylogenetic analyses consistently recovered the familial relationships of (((((Ricaniidae + Issidae) + Flatidae) + Fulgoridae) + Achilidae) + Derbidae) in the amino acid-based analysis, with the placement of Cixiidae and Delphacidae as the earliest-derived lineages of fulgoroid families, whereas the monophyly of Delphacidae was not congruent between tree-constructing algorithms.

Characterization, Comparative Analysis and Phylogenetic Implications of Mitogenomes of Fulgoridae (Hemiptera: Fulgoromorpha)

The complete mitogenomes of nine fulgorid species were sequenced and annotated to explore their mitogenome diversity and the phylogenetics of Fulgoridae. All species are from China and belong to five genera: Dichoptera Spinola, 1839 (Dichoptera sp.); Neoalcathous Wang and Huang, 1989 (Neoalcathous huangshanana Wang and Huang, 1989); Limois Stål, 1863 (Limois sp.); Penthicodes Blanchard, 1840 (Penthicodes atomaria (Weber, 1801), Penthicodes caja (Walker, 1851), Penthicodes variegata (Guérin-Méneville, 1829)); Pyrops Spinola, 1839 (Pyrops clavatus (Westwood, 1839), Pyrops lathburii (Kirby, 1818), Pyrops spinolae (Westwood, 1842)). The nine mitogenomes were 15,803 to 16,510 bp in length with 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs) and a control region (A + T-rich region). Combined with previously reported fulgorid mitogenomes, all PCGs initiate with either the standard start codon of ATN or the nonstandard GTG. The TAA codon was used for termination more often than the TAG codon and the incomplete T codon. The nad1 and nad4 genes varied in length within the same genus. A high percentage of F residues were found in the nad4 and nad5 genes of all fulgorid mitogenomes. The DHU stem of trnV was absent in the mitogenomes of all fulgorids sequenced except Dichoptera sp. Moreover, in most fulgorid mitogenomes, the trnL2, trnR, and trnT genes had an unpaired base in the aminoacyl stem and trnS1 had an unpaired base in the anticodon stem. The similar tandem repeat regions of the control region were found in the same genus. Phylogenetic analyses were conducted based on 13 PCGs and two rRNA genes from 53 species of Fulgoroidea and seven outgroups. The Bayesian inference and maximum likelihood trees had a similar topological structure. The major results show that Fulgoroidea was divided into two groups: Delphacidae and ((Achilidae + (Lophopidae + (Issidae + (Flatidae + Ricaniidae)))) + Fulgoridae). Furthermore, the monophyly of Fulgoridae was robustly supported, and Aphaeninae was divided into Aphaenini and Pyropsini, which includes Neoalcathous, Pyrops, Datua Schmidt, 1911, and Saiva Distant, 1906. The genus Limois is recovered in the Aphaeninae, and the Limoisini needs further confirmation; Dichoptera sp. was the earliest branch in the Fulgoridae.

Structural Features and Phylogenetic Implications of 11 New Mitogenomes of Typhlocybinae (Hemiptera: Cicadellidae)

To explore the characteristics of mitogenomes and discuss the phylogenetic relationships and molecular evolution of the six tribes within Typhlocybinae, 11 complete mitogenomes are newly sequenced and comparatively analyzed. In all of these complete mitogenomes, the number and order of the genes are highly conserved in overall organization. The PCGs initiate with ATN/TTG/GTG and terminate with TAA/TAG/T. Almost all tRNAs are folded into the typical clover-leaf secondary structure. The control region is always variable in length and in numbers of multiple tandem repeat units. The atp8 and nad2 exhibits the highest evolution rate among all the PCGs. Phylogenetic analyses based on whole mitogenome sequences, with three different datasets, using both maximum likelihood and Bayesian methods, indicate the monophyly of Typhlocybinae and its inner tribes, respectively, except for Typhlocybini and Zyginellini that are paraphyletic. Finally, we confirm that Erythroneurini is a subtribe of Dikraneurini.

Characterization and Phylogenetic Analysis of the Mitochondrial Genome Sequence of Nisia fuliginosa (Hemiptera: Fulgoroidea: Meenoplidae)

We explored characterization of the mitochondrial genome (mitogenome or mtGenome) and phylogenetic analysis between 32 Fulgoroid species by sequencing and analyzing the mitogenome of Nisia fuliginosa Yang and Hu, 1985 (Hemiptera: Fulgoroidea: Meenoplidae), thereby making it the first determined mitogenome from the family Meenoplidae. The mitogenome was found to be 15,754 bp in length and contained 13 protein-coding genes (PCGs), 22 tRNA genes, two ribosomal RNA genes (rRNAs), and a control region. All PCGs started with typical ATN codons, except for nad1, which used GTG as the start codon. Canonical TAA termination codons were found in 10 PCGs and the remaining three genes (cox2, nad6, and nad1) had incomplete stop codons T. All tRNAs could fold into typical cloverleaf secondary structures, with the exception of trnC, trnV, and trnS1. Additionally, we compared the AT and GC skews of 13 PCGs of 32 Fulgoroidea mitogenomes, on the L-strand, the AT and GC skews were negative and positive, respectively. However, on the H-strand, the AT skew could be positive or negative and the GC skew was always negative. Phylogenetic results showed that the eight families of Fulgoroidea were divided into two large groups. Delphacidae formed a monophyletic group sister to a clade comprising Meenoplidae and other six families (Fulgoridae, Ricaniidae, Flatidae, Issidae, Caliscelidae, and Achilidae). Meenoplidae was located near the clade of Delphacidae, and Fulgoridae was located near the clade of Meenoplidae. Furthermore, Caliscelidae, Issidae, Ricaniidae, and Flatidae are closely related and they collectively formed a sister group to Achilidae.

A Comparative Analyses of the Complete Mitochondrial Genomes of Fungal Endosymbionts in Sogatella furcifera, White-Backed Planthoppers

Sogatella furcifera Horvath, commonly known as the white-backed planthoppers (WBPH), is an important pest in East Asian rice fields. Fungal endosymbiosis is widespread among planthoppers in the infraorder Fulgoromorpha and suborder Auchenorrhyncha. We successfully obtained complete mitogenome of five WBPH fungal endosymbionts, belonging to the Ophiocordycipitaceae family, from next-generation sequencing (NGS) reads obtained from S. furcifera samples. These five mitogenomes range in length from 55,390 bp to 55,406 bp, which is shorter than the mitogenome of the fungal endosymbiont found in Ricania speculum, black planthoppers. Twenty-eight protein-coding genes (PCGs), 12 tRNAs, and 2 rRNAs were found in the mitogenomes. Two single-nucleotide polymorphisms, two insertions, and three deletions were identified among the five mitogenomes, which were fewer in number than those of four species of Ophiocordycipitaceae, Ophiocordyceps sinensis, Hirsutella thompsonii, Hirsutella rhossiliensis, and Tolypocladium inflatum. Noticeably short lengths (up to 18 bp) of simple sequence repeats were identified in the five WBPH fungal endosymbiont mitogenomes. Phylogenetic analysis based on conserved PCGs across 25 Ophiocordycipitaceae mitogenomes revealed that the five mitogenomes were clustered with that of R. speculum, forming an independent clade. In addition to providing the full mitogenome sequences, obtaining complete mitogenomes of WBPH endosymbionts can provide insights into their phylogenetic positions without needing to isolate the mtDNA from the host. This advantage is of value to future studies involving fungal endosymbiont mitogenomes.

Characterization of Three Complete Mitogenomes of Flatidae (Hemiptera: Fulgoroidea) and Compositional Heterogeneity Analysis in the Planthoppers' Mitochondrial Phylogenomics

Although sequences of mitogenomes have been widely used for investigating phylogenetic relationship, population genetics, and biogeography in many members of Fulgoroidea, only one complete mitogenome of a member of Flatidae has been sequenced. Here, the complete mitogenomes of Cerynia lineola, Cromna sinensis, and Zecheuna tonkinensis are sequenced. The gene arrangements of the three new mitogenomes are consistent with ancestral insect mitogenomes. The strategy of using mitogenomes in phylogenetics remains in dispute due to the heterogeneity in base composition and the possible variation in evolutionary rates. In this study, we found compositional heterogeneity and variable evolutionary rates among planthopper mitogenomes. Phylogenetic analysis based on site-homogeneous models showed that the families (Delphacidae and Derbidae) with high values of Ka/Ks and A + T content tended to fall together at a basal position on the trees. Using a site-heterogeneous mixture CAT + GTR model implemented in PhyloBayes yielded almost the same topology. Our results recovered the monophyly of Fulgoroidea. In this study, we apply the heterogeneous mixture model to the planthoppers’ phylogenetic analysis for the first time. Our study is based on a large sample and provides a methodological reference for future phylogenetic studies of Fulgoroidea.

Introduction to the study of chromosomal and reproductive patterns in Paraneoptera

This paper opens the themed issue (a monograph) "Aberrant cytogenetic and reproductive patterns in the evolution of Paraneoptera", prepared by a Russian-Bulgarian research team on the basis of long-term collaborative studies. In this first part of the issue, we provide the basic introductory information, describe the material involved and the methods applied, and give terminology and nomenclature of used taxonomic names.

The Complete Mitochondrial Genome of Four Hylicinae (Hemiptera: Cicadellidae): Structural Features and Phylogenetic Implications

To reveal mtgenome characterizations and reconstruct phylogenetic relationships of Hylicinae, the complete mtgenomes of four hylicine species, including Nacolus tuberculatus, Hylica paradoxa, Balala fujiana, and Kalasha nativa, were sequenced and comparatively analyzed for the first time. We also carried out the richest (11) subfamily sampling of Cicadellidae to date, and reconstructed phylogenetic relationships of Membracoidea among 61 species based on three datasets using maximum likelihood and Bayesian inference analyses. All new sequenced mtgenomes are molecules ranging from 14,918 to 16,221 bp in length and are double stranded, circular in shape. The gene composition and arrangement of these mtgenomes are consistent with members of Membracoidea. Among 13 protein-coding genes, most show typical ATN start codons and TAR (TAA/TAG) or an incomplete stop codon T-, and several genes start by TTG/GTG. Results of the analysis for sliding window, nucleotide diversity, and nonsynonymous substitution/synonymous substitution indicate cox1 is a comparatively slower-evolving gene while atp8 is the fastest gene. In line with previous researches, phylogenetic results indicate that treehopper families are paraphyletic with respect to family Cicadellidae and also support the monophyly of all involved subfamilies including Hylicinae. Relationships among the four hylicine genera were recovered as (Hylica + (Nacolus + (Balala + Kalasha))).

Portiera Gets Wild: Genome Instability Provides Insights into the Evolution of Both Whiteflies and Their Endosymbionts

Whiteflies (Hemiptera: Sternorrhyncha: Aleyrodidae) are a superfamily of small phloem-feeding insects. They rely on their primary endosymbionts "Candidatus Portiera aleyrodidarum" to produce essential amino acids not present in their diet. Portiera has been codiverging with whiteflies since their origin and therefore reflects its host's evolutionary history. Like in most primary endosymbionts, the genome of Portiera stays stable across the Aleyrodidae superfamily after millions of years of codivergence. However, Portiera of the whitefly Bemisia tabaci has lost the ancestral genome order, reflecting a rare event in the endosymbiont evolution: the appearance of genome instability. To gain a better understanding of Portiera genome evolution, identify the time point in which genome instability appeared and contribute to the reconstruction of whitefly phylogeny, we developed a new phylogenetic framework. It targeted five Portiera genes and determined the presence of the DNA polymerase proofreading subunit (dnaQ) gene, previously associated with genome instability, and two alternative gene rearrangements. Our results indicated that Portiera gene sequences provide a robust tool for studying intergenera phylogenetic relationships in whiteflies. Using these new framework, we found that whitefly species from the Singhiella, Aleurolobus, and Bemisia genera form a monophyletic tribe, the Aleurolobini, and that their Portiera exhibit genome instability. This instability likely arose once in the common ancestor of the Aleurolobini tribe (at least 70 Ma), drawing a link between the appearance of genome instability in Portiera and the switch from multibacteriocyte to a single-bacteriocyte mode of inheritance in this tribe.

Characterization of Two Complete Mitochondrial Genomes of Ledrinae (Hemiptera: Cicadellidae) and Phylogenetic Analysis

Mitochondrial genomes are widely used for investigations into phylogeny, phylogeography, and population genetics. More than 70 mitogenomes have been sequenced for the diverse hemipteran superfamily Membracoidea, but only one partial and two complete mtgenomes mitochondrial genomes have been sequenced for the included subfamily Ledrinae. Here, the complete mitochondrial genomes (mitogenomes) of two additional Ledrinae species are newly sequenced and comparatively analyzed. Results show both mitogenomes are circular, double-stranded molecules, with lengths of 14,927 bp (Tituria sagittata) and 14,918 bp (Petalocephala chlorophana). The gene order of these two newly sequenced Ledrinae is highly conserved and typical of members of Membracoidea. Similar tandem repeats in the control region were discovered in Ledrinae. Among 13 protein-coding genes (PCGs) of reported Ledrinae mitogenomes, analyses of the sliding window, nucleotide diversity, and nonsynonymous substitution (Ka)/synonymous substitution (Ks) indicate atp8 is a comparatively fast-evolving gene, while cox1 is the slowest. Phylogenetic relationships were also reconstructed for the superfamily Membracoidea based on expanded sampling and gene data from GenBank. This study shows that all subfamilies (sensu lato) are recovered as monophyletic. In agreement with previous studies, these results indicate that leafhoppers (Cicadellidae) are paraphyletic with respect to the two recognized families of treehoppers (Aetalionidae and Membracidae). Relationships within Ledrinae were recovered as (Ledra + (Petalocephala + Tituria)).

Evolutionary trends of digestion and absorption in the major insect orders

The spatial organization of digestion, which corresponds to the steps by which the ingested food is hydrolyzed in the different regions of the gut, was described in insects from the major insect orders. The pattern of digestion and absorption in the midgut shows a strong phylogenetic influence, modulated by adaptation to particular feeding habits. Based on this, basic digestive patterns were recognized and were proposed to represent the major ancestors from which the different orders evolved. The putative ancestors chosen to represent different points in the evolution from basal Neoptera to more derived orders were: Neoptera, Polyneoptera, Hemiptera, Hymenoptera-Panorpoidea (Diptera-Lepidoptera), Lepidoptera, and Cyclorrhapha. The basic plan of Neoptera was supposed to be alike that of Polyneoptera, which was hypothesized from studies performed in grasshoppers, crickets and from stick insects. For Holometabola, the basic plan was initially proposed from studies carried out in beetles, bees, nematocerous flies, common flies and also from moths. This review updates the physiological data supporting the putative midgut basic patterns by discussing available data on insects pertaining to different taxa and details the evolutionary trends of midgut function among the major insect orders. Furthermore, by using recent genomic and transcriptome data, this review discusses the few insects for which the spatial organization of midgut absorption is known.

Complete mitochondrial genome of the spotted lanternfly, Lycorma delicatula White, 1845 (Hemiptera: Fulgoridae)

The spotted lanternfly, Lycorma delicatula White, 1845 (Hemiptera: Fulgoridae), is an invasive pest that attacks forest as well as agricultural trees. We sequenced the 15,798-bp long complete mitochondrial genome (mitogenome) of this species; it consists of a typical set of genes (13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes) and one major non-coding A + T-rich region. The orientation and gene order of the L. delicatula mitogenome are identical to that of the ancestral type found in majority of the insects. Bayesian inference (BI) and maximum-likelihood (ML) phylogeny placed the L. delicatula examined in our study, together with other geographical samples of the species in a group with the highest nodal support, forming the subfamily Aphaeninae to which L. delicatula belongs.

Complete mitogenome of Olidiana ritcheriina (Hemiptera: Cicadellidae) and phylogeny of Cicadellidae

BACKGROUND

Coelidiinae, a relatively large subfamily within the family Cicadellidae, includes 129 genera and ∼1,300 species distributed worldwide. However, the mitogenomes of only two species (Olidiana sp. and Taharana fasciana) in the subfamily Coelidiinae have been assembled. Here, we report the first complete mitogenome assembly of the genus Olidiana.

METHODS

Specimens were collected from Wenxian County (Gansu Province, China) and identified on the basis of their morphology. Mitogenomes were sequenced by next-generation sequencing, following which an NGS template was generated, and this was confirmed using polymerase chain reaction and Sanger sequencing. Phylogenic trees were constructed using maximum likelihood and Bayesian analyses.

RESULTS

The mitogenome of O. ritcheriina was 15,166 bp long, with an A + T content of 78.0%. Compared with the mitogenome of other Cicadellidae sp., the gene order, gene content, gene size, base composition, and codon usage of protein-coding genes (PCGs) in O. ritcheriina were highly conserved. The standard start codon of all PCGs was ATN and stop codon was TAA or TAG; COII, COIII, and ND4L ended with a single T. All tRNA genes showed the typical cloverleaf secondary structure, except for trnSer, which did not have the dihydrouridine arm. Furthermore, the secondary structures of rRNAs (rrnL and rrnS) in O. ritcheriina were predicted. Overall, five domains and 42 helices were predicted for rrnL (domain III is absent in arthropods), and three structural domains and 27 helices were predicted for rrnS. Maximum likelihood and Bayesian analyses indicated that O. ritcheriina and other Coelidiinae members were clustered into a clade, indicating the relationships among their subfamilies; the main topology was as follows: (Deltocephalinae + ((Coelidiinae + Iassinae) + ((Typhlocybinae + Cicadellinae) + (Idiocerinae + (Treehopper + Megophthalminae))))). The phylogenetic relationships indicated that the molecular taxonomy of O. ritcheriina is consistent with the current morphological classification.

Characterization of the complete mitochondrial genomes of two species of the genus Aphaena Guérin-Méneville (Hemiptera: Fulgoridae) and its phylogenetic implications

The complete mitochondrial genomes (mitogenomes) of Aphaena (Callidepsa) amabilis and Aphaena (Aphaena) discolor nigrotibiata were sequenced. The mitogenomes of these two species are 16,237 bp and 16,116 bp in length with an A + T content of 77.9% and 77.0%, respectively. Each contains 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and a control region (A + T-rich region). All PCGs initiate with the standard start codon of ATN and terminate with the complete stop codon of TAA or TAG except for atp6, where nad1 ends with an incomplete T codon. All tRNAs have the typical clover-leaf structure except for trnS1 and trnV which have a reduced DHU arm. Moreover, these two mitogenomes have trnL2, trnR and trnT with an unpaired base in the acceptor stem. The putative A + T-rich region includes multiple types of tandem repeat regions. These phylogenetic analyses are reconstructed based on 13 protein-coding genes of 25 auchenorrhynchan mitogenomes, with both maximum likelihood and Bayesian analyses yielding robust identical phylogenetic trees. These results support a monophyletic Auchenorrhyncha and the relationship (Pyrops + (Lycorma + Aphaena)) within Fulgoridae.

Insights into the phylogeny of Hemiptera from increased mitogenomic taxon sampling

Although reconstruction of the phylogeny of Hemiptera has progressed tremendously over the past two decades, some higher-level relationships remain poorly resolved. Here, we investigated the Hemiptera higher-level relationships using full mitochondrial genome data from 357 ingroup species, representing the most comprehensive sampling yet undertaken for reconstructing the phylogeny of this group. In this study, 92 mitochondrial genomes were newly determined. Various data treatment methods and substitution models were applied to tree reconstructions. Effects of compositional heterogeneity, rate heterogeneity, model adequacy and taxon sampling on support values and topological stability were explored. Phylogenetic analyses (1) confirmed the monophyly of Hemiptera under site-heterogeneous model, (2) placed Sternorrhyncha as sister to all other Hemiptera, (3) recovered Coccoidea as the sister taxon of Aphidoidea, followed successively by Aleyrodoidea and Psylloidea, and (4) indicated that the grouping of Coleorrhyncha and Fulgoromorpha was the result of long-branch attraction effect.

Rhodnius prolixus: Identification of missing components of the IMD immune signaling pathway and functional characterization of its role in eliminating bacteria

The innate immune system in insects is regulated by specific signalling pathways. Most immune related pathways were identified and characterized in holometabolous insects such as Drosophila melanogaster, and it was assumed they would be highly conserved in all insects. The hemimetabolous insect, Rhodnius prolixus, has served as a model to study basic insect physiology, but also is a major vector of the human parasite, Trypanosoma cruzi, that causes 10,000 deaths annually. The publication of the R. prolixus genome revealed that one of the main immune pathways, the Immune-deficiency pathway (IMD), was incomplete and probably non-functional, an observation shared with other hemimetabolous insects including the pea aphid (Acyrthosiphon pisum) and the bedbug (Cimex lectularius). It was proposed that the IMD pathway is inactive in R. prolixus as an adaptation to prevent eliminating beneficial symbiont gut bacteria. We used bioinformatic analyses based on reciprocal BLAST and HMM-profile searches to find orthologs for most of the "missing" elements of the IMD pathway and provide data that these are regulated in response to infection with Gram-negative bacteria. We used RNAi strategies to demonstrate the role of the IMD pathway in regulating the expression of specific antimicrobial peptides (AMPs) in the fat body of R. prolixus. The data indicate that the IMD pathway is present and active in R. prolixus, which opens up new avenues of research on R. prolixus-T. cruzi interactions.

The complete mitochondrial genomes of two skipper genera (Lepidoptera: Hesperiidae) and their associated phylogenetic analysis

The systematic positions of two hesperiid genera, Apostictopterus and Barca (Lepidoptera: Hesperiidae), remain ambiguous. We sequenced and annotated the two mitogenomes of Apostictopterus fuliginosus and Barca bicolor and inferred the phylogenetic positions of the two genera within the Hesperiidae based on the available mitogenomes. The lengths of the two circular mitogenomes of A. fuliginosus and B. bicolor are 15,417 and 15,574 base pairs (bp), respectively. These two mitogenomes show similar AT skew, GC skew, codon usage and nucleotide bias of AT: the GC skew of the two species is negative, and the AT skew of A. fuliginosus is negative, while the AT skew of B. bicolor is slightly positive. The largest intergenic spacer is located at the same position between trnQ and ND2 in A. fuliginosus (73 bp) and B. bicolor (72 bp). Thirteen protein-coding genes (PCGs) start with ATN codons except for COI, which starts with CGA. The control regions of both mitogenomes possess a long tandem repeat, which is 30 bp long in A. fuliginosus, and 18 bp in B. bicolor. Bayesian inference and maximum likelihood methods were employed to infer the phylogenetic relationships, which suggested that A. fuliginosus and B. bicolor belong in the subfamily Hesperiinae.

The Complete Mitochondrial Genome of Ugyops sp. (Hemiptera: Delphacidae)

The complete mitochondrial genome (mitogenome) of Ugyops sp. (Hemiptera: Delphacidae) was sequenced, making it the first determined mitogenome from the subfamily Asiracinae, the basal clade of the family Delphacidae. The mitogenome was 15,259 bp in length with A + T content of 77.65% and contained 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a control region. The gene order was identical with that of the ancestral insect. The nucleotide composition analysis indicated that the whole mitogenome was strongly A-skewed (0.288) and highly C-skewed (-0.270). For PCGs on the J-strand, the AT skew was positive, and the GC skew was negative. All PCGs started with canonical ATN codons, except for cox1 and nad5, which used CTG and GTG as start codon, respectively. All tRNAs could fold into typical cloverleaf secondary structures, with the exception of trnS1 (AGN), in which the dihydrouridine arm was reduced to a simple loop. The control region included a poly-T stretch downstream of the small rRNA gene (rrnS), a subregion of higher A + T content and tandemly repeated sequence near trnI. The mitogenome of Ugyops sp. could be very helpful in exploring the diversity and evolution of mitogenomes in Delphacidae.

Complete Mitochondrial Genome of Dinorhynchus dybowskyi (Hemiptera: Pentatomidae: Asopinae) and Phylogenetic Analysis of Pentatomomorpha Species

Dinorhynchus dybowskyi (Hemiptera: Pentatomidae: Asopinae) is used as a biological control agent against various insect pests for its predatory. In the present study, the complete mitochondrial genome (mitogenome) of the species was sequenced using the next-generation sequencing technology. The results showed that the mitogenome is 15,952 bp long, including 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and a control region. Furthermore, the gene order and orientation of this mitogenome are identical to those of most heteropterans. There are 21 intergenic spacers (of length 1-28 bp) and 13 overlapping regions (of length 1-23 bp) throughout the genome. The control region is 1,291 bp long. The start codon of the PCGs is ATN, except cox1 (TTG), and stop codon is TAA, except nad1 (TAG). The 22 tRNAs exhibit a typical cloverleaf secondary structure, except trnS1, which lacks a dihydrouridine (DHU) arm and trnV, where the DHU arm forms a simple loop. The analyses based on nucleotide sequences of the 13 PCGs by Bayesian Inference and maximum likelihood methods. The results support the monophyly of five superfamilies Aradoidea, Pentatomoidea, Pyrrhocoroidea, Lygaeoidea, and Coreoidea. Within Pentatomoidea, the relationship observed is as follows: (Plataspidae + Urostylididae) + (Pentatomidae + (Acanthosomatidae + (Cydnidae + (Scutelleridae + (Dinidoridae + Tessaratomidae))))), and D. dybowskyi was placed in Pentatomidae and close to Eurydema gebleri.

Mitochondrial genomic variation and phylogenetic relationships of three groups in the genus Scaphoideus (Hemiptera: Cicadellidae: Deltocephalinae)

The widespread leafhopper genus Scaphoideus Uhler is the most diverse genus in Scaphoideini and includes some species that are serious pests and vectors of plant pathogens. Here the first Scaphoideus mitogenome sequences are provided for three species, S. maai, S. nigrivalveus and S. varius, representing three main species groups in the Oriental region based on color pattern. The lengths of these three mitogenomes were 15,188, 15,235 and 15,207 bp, respectively. Gene order of three mitogenomes is highly conserved and identical to that of the putative ancestral insect. All three mitogenomes exhibited similar AT nucleotide bias, AT-, GC-skews and codon usage. One large 101 bp intergenic spacer between trnY and cox1 was in S. varius. All 22 tRNA genes had typical cloverleaf secondary structures, except for trnS1 (AGN) which appears to lack the dihydrouridine arm. Genes atp8, nad6 and nad2 were highly variable while cox1 showed the lowest nucleotide diversity. Phylogenetic analyses of three concatenated nucleotide datasets using maximum likelihood and Bayesian methods, comprising all 13 mitogenomes currently available for Membracoidea plus mitogenomes for eight outgroup species representing other cicadomorphan superfamilies, yielded the same topology in which Scaphoideus species formed a monophyletic group within a larger clade comprising three other included Deltocephalinae.

Characterization of the complete mitochondrial genomes of Maiestas dorsalis and Japananus hyalinus (Hemiptera: Cicadellidae) and comparison with other Membracoidea

Only six mitochondrial genomes (mitogenomes) have been previously published for Cicadellidae, the largest family of Hemiptera. This study provides complete, annotated mitogenomes of two additional cicadellid, species Maiestas dorsalis and Japananus hyalinus, and the first comparative mitogenome analysis across the superfamily Membracoidea. The mitogenomes of both sequenced species are similar to those of other studied hemipteran mitogenomes in organization and the lengths are 15,352 and 15,364 bp with an A + T content of 78.7% and 76.6%, respectively. In M. dorsalis, all sequenced genes are arranged in the putative ancestral insect gene arrangement, while the tRNA cluster trnW-trnC-trnY is rearranged to trnY-trnW-trnC in J. hyalinus, the first reported gene rearrangement in Membracoidea. Phylogenetic analyses of the 11 available membracoid mitogenomes and outgroups representing the other two cicadomorphan superfamilies supported the monophyly of Membracoidea, and indicated that treehoppers are a derived lineage of leafhoppers. ML and BI analyses yielded topologies that were congruent except for relationships among included representatives of subfamily Deltocephalinae. Exclusion of third codon positions of PCGs improved some node support values in ML analyses.

Origins of Aminergic Regulation of Behavior in Complex Insect Social Systems

Neuromodulators are conserved across insect taxa, but how biogenic amines and their receptors in ancestral solitary forms have been co-opted to control behaviors in derived socially complex species is largely unknown. Here we explore patterns associated with the functions of octopamine (OA), serotonin (5-HT) and dopamine (DA) in solitary ancestral insects and their derived functions in eusocial ants, bees, wasps and termites. Synthesizing current findings that reveal potential ancestral roles of monoamines in insects, we identify physiological processes and conserved behaviors under aminergic control, consider how biogenic amines may have evolved to modulate complex social behavior, and present focal research areas that warrant further study.

Compositional heterogeneity in true bug mitochondrial phylogenomics

Mitochondrial phylogenomics is often controversial, in particular for inferring deep relationships. The recent rapid increase of mitochondrial genome data provides opportunities for better phylogenetic estimates and assessment of potential biases resulting from heterogeneity in nucleotide composition and mutation rates. Here, we gathered 76 mitochondrial genome sequences for Heteroptera representing all seven infraorders, including 17 newly sequenced mitochondrial genomes. We found strong heterogeneity in base composition and contrasting evolutionary rates among heteropteran mitochondrial genomes, which affected analyses with various datasets and partitioning schemes under site-homogeneous models and produced false groupings of unrelated taxa exhibiting similar base composition and accelerated evolutionary rates. Bayesian analyses using a site-heterogeneous mixture CAT+GTR model showed high congruence of topologies with the currently accepted phylogeny of Heteroptera. The results confirm the monophyly of the six infraorders within Heteroptera, except for Cimicomorpha which was recovered as two paraphyletic clades. The monophyly of Terheteroptera (Cimicomorpha and Pentatomomorpha) and Panheteroptera (Nepomorpha, Leptopodomorpha and Terheteroptera) was recovered demonstrating a significant improvement over previous studies using mitochondrial genome data. Our study shows the power of the site-heterogeneous mixture models for resolving phylogenetic relationships with Heteroptera and provides one more case showing that model adequacy is critical for accurate tree reconstruction in mitochondrial phylogenomics.

Mitochondrial phylogenomics of Hemiptera reveals adaptive innovations driving the diversification of true bugs

Hemiptera, the largest non-holometabolous order of insects, represents approximately 7% of metazoan diversity. With extraordinary life histories and highly specialized morphological adaptations, hemipterans have exploited diverse habitats and food sources through approximately 300 Myr of evolution. To elucidate the phylogeny and evolutionary history of Hemiptera, we carried out the most comprehensive mitogenomics analysis on the richest taxon sampling to date covering all the suborders and infraorders, including 34 newly sequenced and 94 published mitogenomes. With optimized branch length and sequence heterogeneity, Bayesian analyses using a site-heterogeneous mixture model resolved the higher-level hemipteran phylogeny as (Sternorrhyncha, (Auchenorrhyncha, (Coleorrhyncha, Heteroptera))). Ancestral character state reconstruction and divergence time estimation suggest that the success of true bugs (Heteroptera) is probably due to angiosperm coevolution, but key adaptive innovations (e.g. prognathous mouthpart, predatory behaviour, and haemelytron) facilitated multiple independent shifts among diverse feeding habits and multiple independent colonizations of aquatic habitats.

Deep-level phylogeny of Cicadomorpha inferred from mitochondrial genomes sequenced by NGS

Recent development and advancement of next-generation sequencing (NGS) technologies have enabled the determination of mitochondrial genome (mitogenome) at extremely efficiency. In this study, complete or partial mitogenomes for 19 cicadomorphan species and six fulgoroid species were reconstructed by using the method of high-throughput sequencing from pooled DNA samples. Annotation analyses showed that the mitogenomes obtained have the typical insect mitogenomic content and structure. Combined with the existing hemipteran mitogenomes, a series of datasets with all 37 mitochondrial genes (up to 14,381 nt total) under different coding schemes were compiled to test previous hypotheses of deep-level phylogeny of Cicadomorpha. Thirty-seven species representing Cicadomorpha constituted the ingroup. A taxon sampling with nine species from Fulgoroidea and six from Heteroptera comprised the outgroup. The phylogenetic reconstructions congruently recovered the monophyly of each superfamily within Cicadomorpha. Furthermore, the hypothesis (Membracoidea + (Cicadoidea + Cercopoidea)) was strongly supported under the heterogeneous CAT model.

Development and validation of a real-time PCR assay for the glassy-winged sharpshooter Homalodisca vitripennis (Hemiptera: Cicadellidae)

The glassy-winged sharpshooter (Homalodisca vitripennis) is an invasive pest organism, which is found throughout Central America and has recently invaded a few countries in the Pacific Islands. As a carrier of the highly virulent plant pathogenic bacterium Xylella fastidiosa, it is of great economic significance to horticulture and is estimated to cost Californian vineyards over US$100 million per year in control and losses. New Zealand is currently free from this pest, but its recent spread through the Pacific has raised concerns of it establishing in New Zealand, potentially as a result of introduction through human travel. We report here a real-time polymerase chain reaction assay for the rapid identification of H. vitripennis. The assay was extensively validated in silico then optimized and tested against a range of Cicadellidae species, both internationally collected and local to New Zealand. This assay was able to correctly identify H. vitripennis samples, and distinguish between H. vitripennis and close relatives, such as the smoke-tree sharpshooter (Homalodisca liturata) and will be of great benefit to New Zealand biosecurity.

Global map of oxytocin/vasopressin-like neuropeptide signalling in insects

Oxytocin and vasopressin mediate a range of physiological functions that are important for osmoregulation, reproduction, social behaviour, memory and learning. The origin of this signalling system is thought to date back ~600 million years. Oxytocin/vasopressin-like peptides have been identified in several invertebrate species and they appear to be functionally related across the entire animal kingdom. There is little information available about the biology of this peptide G protein-coupled receptor signalling system in insects. Recently over 200 insect genome/transcriptome datasets were released allowing investigation of the molecular structure and phylogenetic distribution of the insect oxytocin/vasopressin orthologue – inotocin peptides and their receptors. The signalling system is present in early arthropods and representatives of some early-diverging lineages. However, Trichoptera, Lepidoptera, Siphonaptera, Mecoptera and Diptera, lack the presence of inotocin genes, which suggests the peptide-receptor system was probably lost in their common ancestor ~280 million-years-ago. In addition we detected several losses of the inotocin signalling system in Hemiptera (white flies, scale insects and aphids), and the complete absence in spiders (Chelicerata). This unique insight into evolutionarily patterns and sequence diversity of neuroendocrine hormones will provide opportunities to elucidate the physiology of the inotocin signalling system in one of the largest group of animals.

Application of RNA-seq for mitogenome reconstruction, and reconsideration of long-branch artifacts in Hemiptera phylogeny

Hemiptera make up the largest nonholometabolan insect assemblage. Despite previous efforts to elucidate phylogeny within this group, relationships among the major sub-lineages remain uncertain. In particular, mitochondrial genome (mitogenome) data are still sparse for many important hemipteran insect groups. Recent mitogenomic analyses of Hemiptera have usually included no more than 50 species, with conflicting hypotheses presented. Here, we determined the nearly complete nucleotide sequence of the mitogenome for the aphid species of Rhopalosiphum padi using RNA-seq plus gap filling. The 15,205 bp mitogenome included all mitochondrial genes except for trnF. The mitogenome organization and size for R. padi are similar to previously reported aphid species. In addition, the phylogenetic relationships for Hemiptera were examined using a mitogenomic dataset which included sequences from 103 ingroup species and 19 outgroup species. Our results showed that the seven species representing the Aleyrodidae exhibit extremely long branches, and always cluster with long-branched outgroups. This lead to the failure of recovering a monophyletic Hemiptera in most analyses. The data treatment of Degen-coding for protein-coding genes and the site-heterogeneous CAT model show improved suppression of the long-branch effect. Under these conditions, the Sternorrhyncha was often recovered as the most basal clade in Hemiptera.

Progress, pitfalls and parallel universes: a history of insect phylogenetics

The phylogeny of insects has been both extensively studied and vigorously debated for over a century. A relatively accurate deep phylogeny had been produced by 1904. It was not substantially improved in topology until recently when phylogenomics settled many long-standing controversies. Intervening advances came instead through methodological improvement. Early molecular phylogenetic studies (1985-2005), dominated by a few genes, provided datasets that were too small to resolve controversial phylogenetic problems. Adding to the lack of consensus, this period was characterized by a polarization of philosophies, with individuals belonging to either parsimony or maximum-likelihood camps; each largely ignoring the insights of the other. The result was an unfortunate detour in which the few perceived phylogenetic revolutions published by both sides of the philosophical divide were probably erroneous. The size of datasets has been growing exponentially since the mid-1980s accompanied by a wave of confidence that all relationships will soon be known. However, large datasets create new challenges, and a large number of genes does not guarantee reliable results. If history is a guide, then the quality of conclusions will be determined by an improved understanding of both molecular and morphological evolution, and not simply the number of genes analysed.