The effectiveness of mitochondrial rRNA gene sequences for the reconstruction of the phylogeny of an insect order (Orthoptera)

Comparative Analysis of Mitogenomes among Five Species of Filchnerella (Orthoptera: Acridoidea: Pamphagidae) and Their Phylogenetic and Taxonomic Implications

Mitogenomes have been widely used for exploring phylogenetic analysis and taxonomic diagnosis. In this study, the complete mitogenomes of five species of Filchnerella were sequenced, annotated and analyzed. Then, combined with other seven mitogenomes of Filchnerella and four of Pamphagidae, the phylogenetic relationships were reconstructed by maximum likelihood (ML) and Bayesian (BI) methods based on PCGs+rRNAs. The sizes of the five complete mitogenomes are Filchnerella sunanensis 15,656 bp, Filchnerella amplivertica 15,657 bp, Filchnerella nigritibia 15,661 bp, Filchnerella pamphagoides 15,661 bp and Filchnerella dingxiensis 15,666 bp. The nucleotide composition of mitogenomes is biased toward A+T. All tRNAs could be folded into the typical clover-leaf structure, except that tRNA Ser (AGN) lacked a dihydrouridine (DHU) arm. The phylogenetic relationships of Filchnerella species based on mitogenome data revealed a general pattern of wing evolution from long wing to increasingly shortened wing.

Comparative mitochondrial genomes of four species of Sinopodisma and phylogenetic implications (Orthoptera, Melanoplinae)

In this study, the whole mitochondrial genomes (mitogenomes) from four species were sequenced. The complete mitochondrial genomes of Sinopodisma pieli, S. houshana, S. qinlingensis, and S. wulingshanensis are 15,857 bp, 15,818 bp, 15,843 bp, and 15,872 bp in size, respectively. The 13 protein-coding genes (PCGs) begin with typical ATN codons, except for COXI in S. qinlingensis, which begins with ACC. The highest A+T content in all the sequenced orthopteran mitogenomes is 76.8% (S. qinlingensis), followed by 76.5% (S. wulingshanensis), 76.4% (S. pieli) and 76.4% (S. houshana) (measured on the major strand). The long polythymine stretches (T-stretch) in the A+T-rich region of the four species are not adjacent to the trnI locus but are inside the stem-loop sequences on the major strand. Moreover, several repeated elements are found in the A+T-rich region of the four species. Phylogenetic analysis based on 53 mitochondrial genomes using Bayesian Inference (BI) and Maximum Likelihood (ML) revealed that Melanoplinae (Podismini) was a monophyletic group; however, the monophyly of Sinopodisma was not supported. These data will provide important information for a better understanding of the phylogenetic relationship of Melanoplinae.

Mitochondrial genomes of three Tetrigoidea species and phylogeny of Tetrigoidea

The mitochondrial genomes (mitogenomes) of Formosatettix qinlingensis, Coptotettix longjiangensis and Thoradonta obtusilobata (Orthoptera: Caelifera: Tetrigoidea) were sequenced in this study, and almost the entire mitogenomes of these species were determined. The mitogenome sequences obtained for the three species were 15,180, 14,495 and 14,538 bp in length, respectively, and each sequence included 13 protein-coding genes (PCGs), partial sequences of rRNA genes (rRNAs), tRNA genes (tRNAs) and a A + T-rich region. The order and orientation of the gene arrangement pattern were identical to that of most Tetrigoidea species. Some conserved spacer sequences between trnS(UCN) and nad1 were useful to identify Tetrigoidea and Acridoidea. The Ka/Ks value of atp8 between Trachytettix bufo and other four Tetrigoidea species indicated that some varied sites in this gene might be related with the evolution of T. bufo. The three Tetrigoidea species were compared with other Caelifera. At the superfamily level, conserved sequences were observed in intergenic spacers, which can be used for superfamily level identification between Tetrigoidea and Acridoidea. Furthermore, a phylogenomic analysis was conducted based on the concatenated data sets from mitogenome sequences of 24 species of Orthoptera in the superorders Caelifera and Ensifera. Both maximum likelihood and bayesian inference analyses strongly supported Acridoidea and Tetrigoidea as forming monophyletic groups. The relationships among six Tetrigoidea species were (((((Tetrix japonica, Alulatettix yunnanensis), Formosatettix qinlingensis), Coptotettix longjiangensis), Trachytettix bufo), Thoradonta obtusilobata).

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.

The complete mitochondrial genome of the Xenocatantops brachycerus (Orthoptera: Catantopidae)

Xenocatantops brachycerus (Orthoptera: Catantopidae), which is widely distributed through China and Southeast Asia, is harmful for the crops. The complete mitochondrial genome of X. brachycerus is 15 605 bp in length and consists of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 A + T-rich region. The gene order of the mitogenome is identical with most orthopteran insects. Most protein-coding genes start with typical ATN codon except for cox1, which initiates with ACC codon instead. While all PCGs use complete stop codons (TAA and TAG). In addition, 13 related species and 2 outgroup taxa were used to construct the phylogenetic tree to further validate the mitogenome of X. brachycerus and research the phylogenetic relationships of Catantopidae.

Utility of characters evolving at diverse rates of evolution to resolve quartet trees with unequal branch lengths: analytical predictions of long-branch effects

BACKGROUND

The detection and avoidance of "long-branch effects" in phylogenetic inference represents a longstanding challenge for molecular phylogenetic investigations. A consequence of parallelism and convergence, long-branch effects arise in phylogenetic inference when there is unequal molecular divergence among lineages, and they can positively mislead inference based on parsimony especially, but also inference based on maximum likelihood and Bayesian approaches. Long-branch effects have been exhaustively examined by simulation studies that have compared the performance of different inference methods in specific model trees and branch length spaces.

RESULTS

In this paper, by generalizing the phylogenetic signal and noise analysis to quartets with uneven subtending branches, we quantify the utility of molecular characters for resolution of quartet phylogenies via parsimony. Our quantification incorporates contributions toward the correct tree from either signal or homoplasy (i.e. "the right result for either the right reason or the wrong reason"). We also characterize a highly conservative lower bound of utility that incorporates contributions to the correct tree only when they correspond to true, unobscured parsimony-informative sites (i.e. "the right result for the right reason"). We apply the generalized signal and noise analysis to classic quartet phylogenies in which long-branch effects can arise due to unequal rates of evolution or an asymmetrical topology. Application of the analysis leads to identification of branch length conditions in which inference will be inconsistent and reveals insights regarding how to improve sampling of molecular loci and taxa in order to correctly resolve phylogenies in which long-branch effects are hypothesized to exist.

CONCLUSIONS

The generalized signal and noise analysis provides analytical prediction of utility of characters evolving at diverse rates of evolution to resolve quartet phylogenies with unequal branch lengths. The analysis can be applied to identifying characters evolving at appropriate rates to resolve phylogenies in which long-branch effects are hypothesized to occur.

Systematics of spiny predatory katydids (Tettigoniidae: Listroscelidinae) from the Brazilian Atlantic Forest based on morphology and molecular data

Listroscelidinae (Orthoptera: Tettigoniidae) are insectivorous Pantropical katydids whose taxonomy presents a long history of controversy, with several genera incertae sedis. This work focused on species occurring in the Brazilian Atlantic Forest, one of the world's most threatened biomes. We examined material deposited in scientific collections and visited 15 conservation units from Rio de Janeiro to southern Bahia between November 2011 and January 2012, catching 104 specimens from 10 conservation units. Based on morphological and molecular data we redefined Listroscelidini, adding a new tribe, new genus and eight new species to the subfamily. Using morphological analysis, we redescribed and added new geographic records for six species, synonymized two species and built a provisional identification key for the Atlantic Forest Listroscelidinae. Molecular results suggest two new species and a new genus to be described, possibly by the fission of the genus Hamayulus. We also proposed a 500 bp region in the final portion of the COI to be used as a molecular barcode. Our data suggest that the Atlantic Forest Listroscelidinae are seriously endangered, because they occur in highly preserved forest remnants, show high rates of endemism and have a narrow geographic distribution. Based on our results, we suggest future collection efforts must take into account the molecular barcode data to accelerate species recognition.

The phylogeny of the Orthoptera (Insecta) as deduced from mitogenomic gene sequences

Background

The phylogeny of the Orthoptera was analyzed based on 6 datasets from 47 orthopteran mitochondrial genomes (mitogenomes). The phylogenetic signals in the mitogenomes were rigorously examined under analytical regimens of maximum likelihood (ML) and Bayesian inference (BI), along with how gene types and different partitioning schemes influenced the phylogenetic reconstruction within the Orthoptera. The monophyly of the Orthoptera and its two suborders (Caelifera and Ensifera) was consistently recovered in the analyses based on most of the datasets we selected, regardless of the optimality criteria.

Results

When the seven NADH dehydrogenase subunits were concatenated into a single alignment (NADH) and were analyzed; a near-identical topology to the traditional morphological analysis was recovered, especially for BI_NADH. In both the concatenated cytochrome oxidase (COX) subunits and COX + cytochrome b (Cyt b) datasets, the small extent of sequence divergence seemed to be helpful for resolving relationships among major Orthoptera lineages (between suborders or among superfamilies). The conserved and variable domains of ribosomal (r)RNAs performed poorly when respectively analyzed but provided signals at some taxonomic levels.

Conclusions

Our findings suggest that the best phylogenetic inferences can be made when moderately divergent nucleotide data from mitogenomes are analyzed, and that the NADH dataset was suited for studying orthopteran phylogenetic relationships at different taxonomic levels, which may have been due to the larger amount of DNA sequence data and the larger number of phylogenetically informative sites.

Taxonomic approach to the tachinid flies Dinera carinifrons (Fallén) (Diptera: Tachinidae) and Dinera fuscata Zhang and Shima using molecular and morphometric data

Molecular phylogenetic and traditional morphometric methods were applied to examine six Palaearctic taxa of the taxonomically difficult tachinid fly genus Dinera Robineau-Desvoidy (Diptera: Tachinidae), with particular reference to D. carinifrons (Fallén) and D. fuscata Zhang and Shima. Results of a phylogenetic analysis based on the mitochondrial markers 12S and 16S rDNA and multivariate statistical analyses of 19 morphometric characters were used to delimit both species. A lectotype was designated for D. carinifrons to stabilize the nomenclature in the group. Dinera carinifrons has a transpalaearctic distribution and is present in Central Europe, especially in high altitudes of the Alps. It differs from the similar and closely related D. fuscata in that it has a slightly larger body size, a dense greyish microtrichosity on the body, and different head proportions. Dinera fuscata, as delimited here, is widespread in the Palaearctic region, including Europe. Slight differences in both molecular and morphometric characters were found between western (Europe and Iran) and eastern (China and Japan) populations of D. fuscata, which are interpreted as an intraspecific variation. Differential diagnosis between D. carinifrons and D. fuscata is provided in the form of a revised portion of the determination key to the Palaearctic Dinera by Zhang and Shima (2006).

[Phylogenetic relationships among Orthoptera insect groups based on complete sequences of 16S ribosomal RNA]

In order to reconstruct a robust phylogenetic relationship among major groups of Orthoptera and to explore the phylogenetic utility and performance of 16S Ribosomal RNA gene, complete sequences of 16S Ribosomal RNA were sequenced from 18 species in 9 families and 4 superfamilies of Orthoptera, and analyzed with other 40 species that have been completely sequenced. The result showed that the average length of 16S Ribosomal RNA was 1 310 bp. The positions of Tridactuloidea and Gryllotalpidae in Orthoptera were uncertain based on the 16S rRNA data, and the phylogenetic relationships of other major groups in Orthoptera were rather robust. Except for Oedipodidae and Gomphoceridae, Acrididae, Catantopidae, and Arcypteridae in Xia's taxonomic system were not monophyletic groups, and the genetic distances among the five groups were small. This indicates that the five families should be combined into one family. The genetic distances among Pamphagidae, Chrotogonidae, and Pyrgomorphidae were also small. The loops of 16S rRNA gene could provide more information than stems when they were used for phylogenetic analysis. Complete sequence of 16S rRNA gene can be used to reconstruct robust phylogenetic relationship at the taxonomic category of species, genera, and suborder in Orthoptera, but lack of resolution at family and superfamily levels.

Phylogeny and classification of the Catantopidae at the tribal level (Orthoptera, Acridoidea)

The grasshopper family Catantopidae is a well-known group, whose members include some of the most notorious agricultural pests. The existing classifications of the family are mostly utilitarian rather than being based on phylogenetic analysis and therefore unable to provide the stability desired for such an economically important group. In the present study, we present the first comprehensive phylogenetic analysis of the family based on morphology. By extensively sampling from the Chinese fauna, we included in the present analysis multiple representatives of each of the previously recognized tribes in the family. In total, we examined 94 genera represented by 240 species and evaluated 116 characters, including 84 for external morphology and 32 for male genitalia. The final matrix consists of 86 ingroup taxa and 88 characters. Our phylogenetic analyses resulted in a high resolution of the basal relationships of the family while showed considerable uncertainty about the relationships among some crown taxa. We further evaluated the usefulness of morphological characters in phylogeny reconstruction of the catantopids by examining character fit to the shortest trees found, and contrary to previous suggestions, our results suggest that genitalia characters are not as informative as external morphology in inferring higher-level relationship. We further suggest that earlier classification systems of grasshoppers in general and Catantopidae in particular most probably consist of many groups that are not natural due the heavy reliance on genitalia features and need to be revised in the light of future phylogenetic studies. Finally, we outlined a tentative classification scheme based on the results of our phylogenetic analysis.

Complete Mitochondrial Genome Sequence of Acrida cinerea (Acrididae: Orthoptera) and Comparative Analysis of Mitochondrial Genomes in Orthoptera

The complete 15,599-bp mitogenome of Acrida cinerea was determined and compared with that of the other 20 orthopterans. It displays characteristic gene content, genome organization, nucleotide composition, and codon usage found in other Caelifera mitogenomes. Comparison of 21 orthopteran sequences revealed that the tRNAs encoded by the H-strand appear more conserved than those by the L-stand. All tRNAs form the typical clover-leaf structure except trnS (agn), and most of the size variation among tRNAs stemmed from the length variation in the arm and loop of TΨC and the loop of DHU. The derived secondary structure models of the rrnS and rrnL from 21 orthoptera species closely resemble those from other insects on CRW except a considerably enlarged loop of helix 1399 of rrnS in Caelifera, which is a potentially autapomorphy of Caelifera. In the A+T-rich region, tandem repeats are not only conserved in the closely related mitogenome but also share some conserved motifs in the same subfamily. A stem-loop structure, 16 bp or longer, is likely to be involved in replication initiation in Caelifera and Grylloidea. A long T-stretch (>17 bp) with conserved stem-loop structure next to rrnS on the H-strand, bounded by a purine at either end, exists in the three species from Tettigoniidae.

Characteristics of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) rRNA genes of Apis mellifera (Insecta: Hymenoptera): structure, organization, and retrotransposable elements

As an accompanying manuscript to the release of the honey bee genome, we report the entire sequence of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) ribosomal RNA (rRNA)-encoding gene sequences (rDNA) and related internally and externally transcribed spacer regions of Apis mellifera (Insecta: Hymenoptera: Apocrita). Additionally, we predict secondary structures for the mature rRNA molecules based on comparative sequence analyses with other arthropod taxa and reference to recently published crystal structures of the ribosome. In general, the structures of honey bee rRNAs are in agreement with previously predicted rRNA models from other arthropods in core regions of the rRNA, with little additional expansion in non-conserved regions. Our multiple sequence alignments are made available on several public databases and provide a preliminary establishment of a global structural model of all rRNAs from the insects. Additionally, we provide conserved stretches of sequences flanking the rDNA cistrons that comprise the externally transcribed spacer regions (ETS) and part of the intergenic spacer region (IGS), including several repetitive motifs. Finally, we report the occurrence of retrotransposition in the nuclear large subunit rDNA, as R2 elements are present in the usual insertion points found in other arthropods. Interestingly, functional R1 elements usually present in the genomes of insects were not detected in the honey bee rRNA genes. The reverse transcriptase products of the R2 elements are deduced from their putative open reading frames and structurally aligned with those from another hymenopteran insect, the jewel wasp Nasonia (Pteromalidae). Stretches of conserved amino acids shared between Apis and Nasonia are illustrated and serve as potential sites for primer design, as target amplicons within these R2 elements may serve as novel phylogenetic markers for Hymenoptera. Given the impending completion of the sequencing of the Nasonia genome, we expect our report eventually to shed light on the evolution of the hymenopteran genome within higher insects, particularly regarding the relative maintenance of conserved rDNA genes, related variable spacer regions and retrotransposable elements.

Phylogeny of the cricket subfamily Eneopterinae (Orthoptera, Grylloidea, Eneopteridae) based on four molecular loci and morphology

The phylogenetic relationships of 39 species of Eneopterinae crickets are reconstructed using four molecular markers (16S rRNA, 12S rRNA, cytochrome b, 18S rRNA) and a large morphological data set. Phylogenetic analysis via direct optimisation of DNA sequence data using parsimony as optimality criterion is done for six combinations of weighting parameter sets in a sensitivity analysis. The results are discussed in a twofold purpose: first, in term of significance of the molecular markers for phylogeny reconstruction in Ensifera, as our study represents the first molecular phylogeny performed for this insect suborder at this level of diversity; second, in term of corroboration of a previous phylogeny of Eneopterinae, built on morphological data alone. The four molecular markers all convey phylogenetic signal, although variously distributed on the tree. The monophyly of the subfamily, that of three over five tribes, and of 10 over 13 genera, are recovered. Finally, previous hypotheses on the evolution of acoustic devices and signals in the Eneopterinae clade are briefly tested, and supported, by our new data set.

Phylogeny of Ensifera (Hexapoda: Orthoptera) using three ribosomal loci, with implications for the evolution of acoustic communication

Representatives of the Orthopteran suborder Ensifera (crickets, katydids, and related insects) are well known for acoustic signals produced in the contexts of courtship and mate recognition. We present a phylogenetic estimate of Ensifera for a sample of 51 taxonomically diverse exemplars, using sequences from 18S, 28S, and 16S rRNA. The results support a monophyletic Ensifera, monophyly of most ensiferan families, and the superfamily Gryllacridoidea which would include Stenopelmatidae, Anostostomatidae, Gryllacrididae, and Lezina. Schizodactylidae was recovered as the sister lineage to Grylloidea, and both Rhaphidophoridae and Tettigoniidae were found to be more closely related to Grylloidea than has been suggested by prior studies. The ambidextrously stridulating haglid Cyphoderris was found to be basal (or sister) to a clade that contains both Grylloidea and Tettigoniidae. Tree comparison tests with the concatenated molecular data found our phylogeny to be significantly better at explaining our data than three recent phylogenetic hypotheses based on morphological characters. A high degree of conflict exists between the molecular and morphological data, possibly indicating that much homoplasy is present in Ensifera, particularly in acoustic structures. In contrast to prior evolutionary hypotheses based on most parsimonious ancestral state reconstructions, we propose that tegminal stridulation and tibial tympana are ancestral to Ensifera and were lost multiple times, especially within the Gryllidae.

Secondary structure, high variability and conserved motifs for domain III of 12S rRNA in the Arthropleona (Hexapoda; Collembola)

The robustness of different hypothetical structural models for ribosomal RNAs can be established by comparing sequences from widely different taxonomic groups. Secondary structure models of the two mitochondrial ribosomal subunits have been proposed for a large number of pterygote insects, but little information is available for the more ancient entognath hexapods. We have investigated the most frequently sequenced of the four domains of the mitochondrial small subunit rRNA in twenty-two collembolan species in the taxon Arthropleona. We provide secondary structure models of this third domain for representative species, and a consensus based on all species studied. This consensus is in partial agreement with previous models. High levels of variation, in terms of length and of primary sequence, are present in the peripheral portions of the domain. Some of the structural elements differ more among genera of springtails than among insect orders. Conversely, a limited number of structural differences compared with other taxa have been detected in the core regions.

Aligned 18S and Insect Phylogeny

The nuclear small subunit rRNA (18S) has played a dominant role in the estimation of relationships among insect orders from molecular data. In previous studies, 18S sequences have been aligned by unadjusted automated approaches (computer alignments that are not manually readjusted), most recently with direct optimization (simultaneous alignment and tree building using a program called "POY"). Parsimony has been the principal optimality criterion. Given the problems associated with the alignment of rRNA, and the recent availability of the doublet model for the analysis of covarying sites using Bayesian MCMC analysis, a different approach is called for in the analysis of these data. In this paper, nucleotide sequence data from the 18S small subunit rRNA gene of insects are aligned manually with reference to secondary structure, and analyzed under Bayesian phylogenetic methods with both GTR+I+G and doublet models in MrBayes. A credible phylogeny of Insecta is recovered that is independent of the morphological data and (unlike many other analyses of 18S in insects) not contradictory to traditional ideas of insect ordinal relationships based on morphology. Hexapoda, including Collembola, are monophyletic. Paraneoptera are the sister taxon to a monophyletic Holometabola but weakly supported. Ephemeroptera are supported as the sister taxon of Neoptera, and this result is interpreted with respect to the evolution of direct sperm transfer and the evolution of flight. Many other relationships are well-supported but several taxa remain problematic, e.g., there is virtually no support for relationships among orthopteroid orders. A website is made available that provides aligned 18S data in formats that include structural symbols and Nexus formats.

Long-branch attraction phenomenon and the impact of among-site rate variation on rodent phylogeny

The phylogenetic relationships among major lineages of rodents is one of the issues most debated by both paleontologists and molecular biologists. In the present study, we have analyzed all complete mammalian mitochondrial genomes available in the databases, including five rodent species (rat, mouse, dormouse, squirrel and guinea-pig). Phylogenetic analyses were performed on H-strand amino acid sequences by means of maximum-likelihood and on H-strand protein-coding and ribosomal genes by means of distance methods. Also, log-likelihood ratio tests were applied to different tree topologies under the assumption of rodent monophyly, paraphyly or polyphyly. The analyses significantly rejected rodent monophyly and showed the existence of two differentiated clades, one containing non-murids (dormouse, squirrel and guinea-pig) and the other containing murids (rat and mouse). Long-branch attraction between murids and the outgroups could not be responsible for the existence of two different rodent clades, as no significant differences in evolutionary rate have been observed, except in the case of the squirrel, which shows a lower rate. The impact of among-site rate variation models on the phylogeny of rodents has been evaluated using the gamma distribution model. Results have shown that relationships among rodents remained unchanged, and the general topology of the tree was not affected, even though some branches were not properly resolved, most likely due to a lack of fit between estimated and real rate heterogeneity parameters.

Secondary structure and conserved motifs of the frequently sequenced domains IV and V of the insect mitochondrial large subunit rRNA gene

We have analysed over 400 partial insect mitochondrial large subunit (mit LSU) sequences in order to identify conserved motifs and secondary structures for domains IV and V of this gene. Most of the secondary structure elements described by R. R. Gutell et al. (unpublished) for the LSU were identified. However, we present structures for helices 84 and 91 that are not recognized in previous universal models. The portion of the 16S gene containing domains IV and V is frequently sequenced in insect molecular systematic studies so we have many more sequences than previous studies which focused on the complete mitochondrial LSU molecule. In addition, we have the advantage of investigating several sets of closely related taxa. Aligned sequences from thirteen insect orders and nine secondary structure diagrams are presented. These conserved sequence motifs and their associated secondary structure elements can now be used to facilitate the alignment of other insect mit LSU sequences.

Phylogenetic relationships of north American field crickets inferred from mitochondrial DNA data

A well-supported molecular phylogeny for North American Gryllus species based on a combined data set of mitochondrial (mt) DNA is presented. A total of 26 individuals representing 13 populations of 11 species of the genus Gryllus and 4 individuals of two outgroup species, Teleogryllus oceanicus and Acheta domestica, were sampled in this study. The complete cytochrome b gene (1036 bp) and a 500-bp fragment of the 16S rRNA gene were sequenced for each individual. Since results from separate analyses of the cytochrome b and 16S data sets, as well as a previously published mtDNA restriction-site data set, were not conflicting, all data were combined for phylogenetic analyses. The clade of European Gryllus was clearly separated from the North American clade. The amount of sequence divergence between these clades was significantly greater than within the clades, suggesting a basal drift-vicariant event in the genus. This is the first phylogenetic analysis of North American Gryllus that includes western species. Four well-supported groups were identified but their relationships showed no clear east-west structure. Our phylogeny supports the recent reassignment of G. integer Scudder 1901 from Texas to G. texensis Cade and Otte 2000. The evolution of cricket song and life cycle is discussed using the new phylogenetic framework.

Phylogenetic analysis of mitochondrial LSU rRNA in oniscids

The phylogenetic relationships among oniscids (Crustacea, Isodopa) remain contradictory despite numerous morphological studies. We have investigated them using molecular data. Partial sequences of the mitochondrial LSU rRNA gene were obtained from 42 species of aquatic and terrestrial crustaceans from 31 genera. This gene provided well-supported information, notwithstanding the high taxonomic level of this study, indicating a useful amount of variation despite the noise due to multiple substitutions. The phylogenetic inferences demonstrated that a) Crinocheta and Synocheta sections are monophyletic and sister-groups, b) Ligiidae and Tylidae representatives are in a basal position compared to other oniscids, c) Helleria brevicornis, the only representative of the Helleriinae subfamily, has undergone different evolution, d) the relationships between aquatic isopods and ancient groups of Oniscidea are not resolved, probably due to fast radiation not discriminated by the molecular phylogeny.

The current state of insect molecular systematics: a thriving Tower of Babel

Insect molecular systematics has undergone remarkable recent growth. Advances in methods of data generation and analysis have led to the accumulation of large amounts of DNA sequence data from most major insect groups. In addition to reviewing theoretical and methodological advances, we have compiled information on the taxa and regions sequenced from all available phylogenetic studies of insects. It is evident that investigators have not usually coordinated their efforts. The genes and regions that have been sequenced differ substantially among studies and the whole of our efforts is thus little greater than the sum of its parts. The cytochrome oxidase I, 16S, 18S, and elongation factor-1 alpha genes have been widely used and are informative across a broad range of divergences in insects. We advocate their use as standards for insect phylogenetics. Insect molecular systematics has complemented and enhanced the value of morphological and ecological data, making substantial contributions to evolutionary biology in the process. A more coordinated approach focused on gathering homologous sequence data will greatly facilitate such efforts.

Assembly of a complete zebrafish mitochondrial 16S rRNA gene from overlapping expressed sequence tags

A complete zebrafish mitochondrial 16S ribosomal RNA gene was assembled from our existing zebrafish EST clones by aligning them with the carp mitochondria 16S rRNA sequence. The overall homology between our assembled zebrafish mt 16S rRNA and the carp mt 16S rRNA is 83.5%. As the number of zebrafish ESTs grows, the assembly of more full-length cDNA sequences from overlapping EST data could be expected.

Phylogenetic relationships among Acanthamoeba spp. based on PCR-RFLP analyses of mitochondrial small subunit rRNA gene

We investigated the value of mitochondrial small subunit rRNA gene (mt SSU rDNA) PCR-RFLP as a taxonomic tool for Acanthamoeba isolates with close inter-relationships. Twenty-five isolates representing 20 species were included in the analysis. As in nuclear 18S rDNA analysis, two type strains (A. astronyxis and A. tubiashi) of morphological group 1 diverged earliest from the other strains, but the divergence between them was less than in 18S riboprinting. Acanthamoeba griffini of morphological group 2 branched between pathogenic (A. culbertsoni A-1 and A. healyi OC-3A) and nonpathogenic (A. palestinensis Reich, A. pustulosa GE-3a, A. royreba Oak Ridge, and A lenticulata PD2S) strains of morphological group 3. Among the remaining isolates of morphological group 2, the Chang strain had the identical mitochondrial riboprints as the type strain of A. hatchetti. AA2 and AA1, the type strains of A. divionensis and A. paradivionensis, respectively, had the identical riboprints as A. quina Vil3 and A. castellanii Ma. Although the branching orders of A. castellanii Neff, A. polyphaga P23, A. triangularis SH621, and A. lugdunensis L3a were different from those in 18S riboprinting analysis, the results obtained from this study generally coincided well with those from 18S riboprinting. Mitochondrial riboprinting may have an advantage over nuclear 18S rDNA riboprinting because the mt SSU rDNAs do not seem to have introns that are found in the 18S genes of Acanthamoeba and that distort phylogenetic analyses.

Chloroplast-expressed glutamine synthetase (ncpGS): potential utility for phylogenetic studies with an example from Oxalis (Oxalidaceae)

Chloroplast-expressed glutamine synthetase (ncpGS), a nuclear-encoded gene containing several introns, is introduced as a tool for phylogenetic studies at lower taxonomic levels. This gene is a member of a multigene family, but it diverged long ago from the cytosolic-expressed members of the family and appears to be single copy in the majority of taxa examined to date. The conservation of both coding sequence and position of introns has allowed the design of primers for use in a broad range of dicot taxa to amplify and sequence a region of ncpGS that contains four introns. The utility of this region in phylogenetic studies of congeneric species is illustrated by an example using eight Oxalis species. The four introns in these taxa are typical in size (76 to 136 bp), base composition (high T content), and structure (e.g., sequence of splice sites and putative branch points) for plant internal introns. Levels of variation among these ncpGS sequences compare favorably with those of the internal transcribed spacer of nuclear ribosomal DNA (ITS) from the same taxa, and results of phylogenetic analysis of ncpGS data are generally congruent with previous results using ITS.

The phylogeny of the Caelifera (Insecta, Orthoptera) as deduced from mtrRNA gene sequences

Fragments of both mitochondrial ribosomal RNA genes of 32 caeliferan taxa (representing six of the seven superfamilies) and six outgroup Orthopteroids were sequenced. The combined alignment length was 630 bp after removal of all ambiguously aligned positions. Separation for the basal taxa was problematic and analysis using the LogDet transformation indicated that shared base composition biases were a confounding factor. The suborder Caelifera and all traditional caeliferan superfamilies except the Pamphagoidea are retrieved as monophyletic groups, though the Eumastacoidea lack significant bootstrap support. Of the traditional pamphagoid taxa, the Pamphagidae is embedded between classically acridid subfamilies, whereas Pyrgomorphidae is placed close to the Pneumoroidea. The morphological similarities of the Pyrgomorphidae and Pamphagidae may thus be homoplasic. A consensus tree based on five different methods of analysis indicated the following order: (Tridactyloidea, Tetrigoidea (Eumastacidae, Proscopiidae (Pneumoridae, Pyrgomorphidae (Acrididae + Pamphagidae)))).