Phylogeny and the evolution of acoustic communication in extant Ensifera (Insecta, Orthoptera)

Ensifera present an appropriate and interesting model for the study of acoustic communication, because of their diverse signal and communication modalities, and due to their accessibility for field and laboratory studies. Several hypotheses have been proposed to explain the acoustic evolution of Ensifera, but they were elaborated without any reference to a falsifiable phylogeny, and were consequently highly speculative. Similarly, phylogenetic relationships between ensiferan clades have not hitherto been studied using modern standard methodology, and the sole cladistic analysis by Gwynne in 1995 was methodologically flawed. No sound hypothesis therefore currently exists for ensiferan phylogeny, which precludes historical analysis of their communication modalities. In the present paper, the phylogeny is established on the basis of morpho‐anatomical characters and used to analyse the evolution of acoustic communication in this clade by mapping the characters related to auditory and stridulatory structures onto the resultant trees. Cladistic analyses resulted in two equi‐parsimonious cladograms (length 154, C 64, CI 58, RI 61) with the following topologies: (1) [(Grylloidea–Gryllotalpidae) (Rhaphidophoridae (Schizodactylidae (Gryllacrididae ((Stenopelmatidae–Cooloola) (Anostostomatidae (Prophalangopsis (Cyphoderris (Tettigoniidae–Lezina))))))))] (2) [(Grylloidea–Gryllotalpidae)(Rhaphidophoridae (Schizodactylidae (Gryllacrididae–Cooloola–(Stenopelmatidae (Anostostomatidae (Prophalangopsis (Cyphoderris (Tettigoniidae–Lezina))))))))]. According to these topologies, Ensifera were ancestrally devoid of acoustic and hearing systems. An acoustic (tegminal or femoro‐abdominal) apparatus appeared a number of times independently with convergent structures. Similarly, tibial tympana developed several times independently. Moreover, four hypotheses (each according to a definite pattern of character transformation) can be proposed to explain the evolution of acoustic communication in the different ensiferan clades and relate it to a definite communicatory context. These hypotheses do not apply equally to ensiferan subclades. Grylloidea and Gryllotalpoidea could have experienced convergently a direct development of an intraspecific acoustic communication. Acoustic communication in Tettigoniidea has evolved more ambiguously, and may either have resulted from a direct evolution analogous to that having occurred in Gryllidea, or have developed in a completely different behavioural context. Future studies of acoustic communication in the different ensiferan clades will have to take into account the fact that the involved structures most often are not homologous and that their evolution may not have taken place in similar conditions. Different hypotheses of acoustic communication evolution may apply to different clades, and there may be no single explanation for acoustic communication in Ensifera.     

The phylogeny of Orthoptera inferred from mtDNA and description of Elimaea cheni （Tettigoniidae： Phaneropterinae） mitogenome

The complete 15,831 bp nucleotide sequence of the mitochondrial genome from Elimaea cheni(Phaneropterinae)was determined.The putative initiation codon for cox1 was TTA.The phylogeny of Orthoptera based on different mtDNA datasets were analyzed with maximum likelihood(ML)and Bayesian inference(BI).When all 37 genes(mtDNA)were analyzed simultaneously,the monophyly of Caelifera and Ensifera were recovered in the context of our taxon sampling.The phylogeny of Orthoptera was largely consistent with previous phylogenetie hypotheses.Rhaphidophoridae to be a sister group of Tettigoniidae,and the relationships among four subfamilies of Tettigoniidae were(Phaneropterinae+(Conocephalinae+(Bradyporinae+Tettigoniinae))).Pyrgomorphidae was the most basal group of Caelifera.The relationships among six acridid subfamilies were(Oedipodinae+(Acridinae+(Gomphocerinae+(Oxyinae+(Calliptaminae +Cyrtacanthaeridinae))))).However,we did not recover a monophyletic Grylloidea.Myrmecophilidae clustered into one clade with Gryllotalpidae instead of with Gryllidae.ML and BI analyses of all protein coding genes(using all nucleotide sequence data or excluding the third codon position,and amino acid sequences)revealed a topology identical to that of the entire mtDNA genome dataset.However,22 tRNAs genes excluding the DHU loop and T()C loop(TRNA),and two rRNA genes(RRNA)perform poorly when analyzed as single dataset.Our results suggest that the best phylogenetie inferences were ML and BI methods based on total mtDNA.Excluding tRNA genes,rRNA genes and the third codon position of protein coding genes from dataset and converting nucleotide sequences to amino acid sequences do not positively affect phylogenetic reconstruction.     

One hundred years of instability in ensiferan relationships

Although Ensifera is a major insect model group, its phylogenetic relationships have been understudied so far. Few phylogenetic hypotheses have been proposed, either with morphological or molecular data. The largest dataset ever used for phylogeny reconstruction on this group is molecular (16S rRNA, 18S rRNA and 28S rRNA sequences for 51 ensiferan species), which has been used twice with different resultant topologies. However, only one of these hypotheses has been adopted commonly as a reference classification. Here we re‐analyse this molecular dataset with different methods and parameters to test the robustness and the stability of the adopted phylogeny. Our study reveals the instability of phylogenetic relationships derived from this dataset, especially for the deepest nodes of the group, and suggests some guidelines for future studies. The comparison between the different classifications proposed in the past 70 years for Ensifera and our results allows the identification of potential monophyletic clades (katydids, mole crickets, scaly crickets + Malgasia, true crickets, leaf roller crickets, cave crickets) and the remaining unresolved clades (wetas, Jerusalem crickets and most of the highest rank clades) in Ensifera phylogeny.     

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.     

A phylogenetic analysis of the adipokinetic neuropeptides of Ensifera

Abstract.  Adipokinetic neuropeptides, from the corpora cardiaca of various species of the suborder Ensifera, encompassing members of all superfamilies (except the Gryllacridoidea), were isolated by liquid chromatography, and identified structurally by comparison of retention times and mass spectrometry data with respect to information from known members of this peptide family. Ensiferan species always contain only one adipokinetic hormone (AKH) peptide, as assessed for a few species by monitoring typical AKH mass peaks from a crude corpora cardiaca extract. This AKH is an octapeptide, and is either Scg-AKH-II (pGlu-Leu-Asn-Phe-Ser-Thr-Gly-Trp amide) which occurs in all Tettigoniidea (except Schizodactyloidea) and in Gryllotalpoidea, or Grb-AKH (pGlu-Val-Asn-Phe-Ser-Thr-Gly-Trp amide) which occurs in Grylloidea (except Gryllotalpoidea) and Schizodactyloidea. Using the structural information of these neuropeptides in conjunction with morpho-anatomical characters, these data are interpreted in a phylogenetic framework. The lack of a decapeptide and the presence of the octapeptide Scg-AKH-II are ancestral in Ensifera. The ancestral Scg-AKH-II twice underwent an independent and convergent modification to Grb-AKH.     

Phylogenetic relationships of freshwater bryozoans (Ectoprocta, Phylactolaemata) inferred from mitochondrial ribosomal DNA sequences

Most species of freshwater bryozoans (Ectoprocta: Phylactolaemata) have few morphological distinctions, and within phylactolaemates, the morphology of the statoblast has been used to determine evolutionary relationships. Here, two controversial phylogenies have been proposed for phylactolaemates with regard to the relationship of Lophopodidae to other families. Two plumatellid genera, Gelatinella and Hyalinella , are candidates for the ancestral type of lophopodids. In addition, the coexistence of spines on the surfaces of the statoblast has led to the suggestion that lophopodids are closely related to the family Cristatellidae. In this study, we analysed mitochondrial DNA sequences of the 12S and 16S rDNA genes of 10 phylactolaemate species. Our results suggest that plumatellids may not be a direct ancestral group of lophopodids and that cristatellids are not a sister group of lophopodids. Fredericella , which was previously thought to be an ancestral group, was revealed to be derived. In addition, our results suggest that Stephanella is the most basal phylactolaemate. Mapping morphological characteristics onto the sequence-based phylogenetic tree revealed convergent evolution of statoblast characters.     

The age and phylogeny of wood boring weevils and the origin of subsociality

A large proportion of the hyperdiverse weevils are wood boring and many of these taxa have subsocial family structures. The origin and relationship between certain wood boring weevil taxa has been problematic to solve and hypotheses on their phylogenies change substantially between different studies. We aimed at testing the phylogenetic position and monophyly of the most prominent wood boring taxa Scolytinae, Platypodinae and Cossoninae, including a range of weevil outgroups with either the herbivorous or wood boring habit. Many putatively intergrading taxa were included in a broad phylogenetic analysis for the first time in this study, such as Schedlarius, Mecopelmus, Coptonotus, Dactylipalpus, Coptocorynus and allied Araucariini taxa, Dobionus, Psepholax, Amorphocerus-Porthetes, and some peculiar wood boring Conoderini with bark beetle behaviour. Data analyses were based on 128 morphological characters, rDNA nucleotides from the D2-D3 segment of 28S, and nucleotides and amino acids from the protein encoding gene fragments of CAD, ArgK, EF-1α and COI. Although the results varied for some of the groups between various data sets and analyses, one may conclude the following from this study: Scolytinae and Platypodinae are likely sister lineages most closely related to Coptonotus; Cossoninae is monophyletic (including Araucariini) and more distantly related to Scolytinae; Amorphocerini is not part of Cossoninae and Psepholax may belong to Cryptorhynchini. Likelihood estimation of ancestral state reconstruction of subsociality indicated five or six origins as a conservative estimate. Overall the phylogenetic results were quite dependent on morphological data and we conclude that more genetic loci must be sampled to improve phylogenetic resolution. However, some results such as the derived position of Scolytinae were consistent between morphological and molecular data. A revised time estimation of the origin of Curculionidae and various subfamily groups were made using the recently updated fossil age of Scolytinae (100 Ma), which had a significant influence on node age estimates.     

Medusozoan phylogeny and character evolution clarified by new large and small subunit rDNA data and an assessment of the utility of phylogenetic mixture models

A newly compiled data set of nearly complete sequences of the large subunit of the nuclear ribosome (LSU or 28S) sampled from 31 diverse medusozoans greatly clarifies the phylogenetic history of Cnidaria. These data have substantial power to discern among many of the competing hypotheses of relationship derived from prior work. Moreover, LSU data provide strong support at key nodes that were equivocal based on other molecular markers. Combining LSU sequences with those of the small subunit of the nuclear ribosome (SSU or 18S), we present a detailed working hypothesis of medusozoan relationships and discuss character evolution within this diverse clade. Stauromedusae, comprising the benthic, so-called stalked jellyfish, appears to be the sister group of all other medusozoans, implying that the free-swimming medusa stage, the motor nerve net, and statocysts of ecto-endodermal origin are features derived within Medusozoa. Cubozoans, which have had uncertain phylogenetic affinities since the elucidation of their life cycles, form a clade-named Acraspeda-with the scyphozoan groups Coronatae, Rhizostomeae, and Semaeostomeae. The polyps of both cubozoans and hydrozoans appear to be secondarily simplified. Hydrozoa is comprised by two well-supported clades, Trachylina and Hydroidolina. The position of Limnomedusae within Trachylina indicates that the ancestral hydrozoan had a biphasic life cycle and that the medusa was formed via an entocodon. Recently hypothesized homologies between the entocodon and bilaterian mesoderm are therefore suspect. Laingiomedusae, which has often been viewed as a close ally of the trachyline group Narcomedusae, is instead shown to be unambiguously a member of Hydroidolina. The important model organisms of the Hydra species complex are part of a clade, Aplanulata, with other hydrozoans possessing direct development not involving a ciliated planula stage. Finally, applying phylogenetic mixture models to our data proved to be of little additional value over a more traditional phylogenetic approach involving explicit hypothesis testing and bootstrap analyses under multiple optimality criteria. [18S; 28S; Cubozoa; Hydrozoa; medusa; molecular systematics; polyp; Scyphozoa; Staurozoa.].     

Phylogenetic investigations of Antarctic notothenioid fishes (Perciformes: Notothenioidei) using complete gene sequences of the mitochondrial encoded 16S rRNA

The Notothenioidei dominates the fish fauna of the Antarctic in both biomass and diversity. This clade exhibits adaptations related to metabolic function and freezing avoidance in the subzero Antarctic waters, and is characterized by a high degree of morphological and ecological diversity. Investigating the macroevolutionary processes that may have contributed to the radiation of notothenioid fishes requires a well-resolved phylogenetic hypothesis. To date published molecular and morphological hypotheses of notothenioids are largely congruent, however, there are some areas of significant disagreement regarding higher-level relationships. Also, there are critical areas of the notothenioid phylogeny that are unresolved in both molecular and morphological phylogenetic analyses. Previous molecular phylogenetic analyses of notothenioids using partial mtDNA 12S and 16S rRNA sequence data have resulted in limited phylogenetic resolution and relatively low node support. One particularly controversial result from these analyses is the paraphyly of the Nototheniidae, the most diverse family in the Notothenioidei. It is unclear if the phylogenetic results from the 12S and 16S partial gene sequence dataset are due to limited character sampling, or if they reflect patterns of evolutionary diversification in notothenioids. We sequenced the complete mtDNA 16S rRNA gene for 43 notothenioid species, the largest sampling to-date from all eight taxonomically recognized families. Phylogenetic analyses using both maximum parsimony and maximum likelihood resulted in well-resolved trees with most nodes supported with high bootstrap pseudoreplicate scores and significant Bayesian posterior probabilities. In all analyses the Nototheniidae was monophyletic. Shimodaira–Hasegawa tests were able to reject two hypotheses that resulted from prior morphological analyses. However, despite substantial resolution and node support in the 16S rRNA trees, several phylogenetic hypotheses among closely related species and clades were not rejected. The inability to reject particular hypotheses among species in apical clades is likely due to the lower rate of nucleotide substitution in mtDNA rRNA genes relative to protein coding regions. Nevertheless, with the most extensive notothenioid taxon sampling to date, and the much greater phylogenetic resolution offered by the complete 16S rRNA sequences over the commonly used partial 12S and 16S gene dataset, it would be advantageous for future molecular investigations of notothenioid phylogenetics to utilize at the minimum the complete gene 16S rRNA dataset.     

A duplicate gene rooting of seed plants and the phylogenetic position of flowering plants

Flowering plants represent the most significant branch in the tree of land plants, with respect to the number of extant species, their impact on the shaping of modern ecosystems and their economic importance. However, unlike so many persistent phylogenetic problems that have yielded to insights from DNA sequence data, the mystery surrounding the origin of angiosperms has deepened with the advent and advance of molecular systematics. Strong statistical support for competing hypotheses and recent novel trees from molecular data suggest that the accuracy of current molecular trees requires further testing. Analyses of phytochrome amino acids using a duplicate gene-rooting approach yield trees that unite cycads and angiosperms in a clade that is sister to a clade in which Gingko and Cupressophyta are successive sister taxa to gnetophytes plus Pinaceae. Application of a cycads + angiosperms backbone constraint in analyses of a morphological dataset yields better resolved trees than do analyses in which extant gymnosperms are forced to be monophyletic. The results have implications both for our assessment of uncertainty in trees from sequence data and for our use of molecular constraints as a way to integrate insights from morphological and molecular evidence.     

Phylogenetic systematics of the colorful, cyanide-producing millipedes of Appalachia (Polydesmida, Xystodesmidae, Apheloriini) using a total evidence Bayesian approach

Here, we provide an exemplar-approach phylogeny of the xystodesmid millipede tribe Apheloriini with a focus on genus-group relationships-particularly of the genus Brachoria. Exemplars for the phylogenetic analysis were chosen to represent the maximum breadth of morphological diversity within all nominal genera in the tribe Apheloriini, and to broadly sample the genus Brachoria. In addition, three closely related tribes were used (Rhysodesmini, Nannariini, and Pachydesmini). Morphological and DNA sequence data were scored for Bayesian inference of phylogeny. Phylogenetic analysis resulted in polyphyletic genera Brachoria and Sigmoria, a monophyletic Apheloriini, and a "southern clade" that contains most of the tribal species diversity. We used this phylogeny to track morphological character histories and reconstruct ancestral states using stochastic character mapping. Based on the findings from the character mapping study, the diagnostic feature of the genus Brachoria, the cingulum, evolved independently in two lineages. We compared our phylogeny against prior classifications using Bayes factor hypothesis-testing and found that our phylogenetic hypothesis is inconsistent with the previous hypotheses underlying the most recent classification. With our preferred total-evidence phylogeny as a framework for taxonomic modifications, we describe a new genus, Appalachioria; supply phylogenetic diagnoses of monophyletic taxa; and provide a phylogeny-based classification for the tribe Apheloriini.     

Molecular phylogeny of the plant bugs (Heteroptera: Miridae) and the evolution of feeding habits

The first comprehensive cladistic analysis of Miridae, the plant bugs, is presented based on analysis of 3935 base pairs of mitochondrial (16S, COI) and nuclear (18S, 28SD3) DNA for 91 taxa in seven subfamilies. Data were analysed using maximum likelihood (ML), parsimony and Bayesian inference (BI) phylogenetic frameworks. The phylogenetic results are compared with previous hypotheses of higher relationships in the family using alternative hypothesis tests. A Bayesian relaxed molecular clock is used to examine divergence times, and ancestral feeding habits are reconstructed using parsimony and a Bayesian approach. Clades recovered in all analyses are as follows: Cimicomorpha, Miroidea and Miridae; Bryocorinae: Bryocorini; Stenodemini; Mirinae; Deraeocorinae (Clevinemini + Deraeocorini); Cylapinae; Isometopinae; Bryocorinae: Dicyphini; Orthotylini; Phylinae (Phylini + Pilophorini), and Phylinae as sister group to all the remaining mirid taxa. These results are largely congruent with former hypotheses based on morphological data with respect to the monophyly of various subfamilies and tribes; however, our results indicate that the subfamily Bryocorinae is not monophyletic, as the two tribes, Dicypini and Bryocorini, were separated in the phylogenetic results. Divergence time estimates indicate that the radiation of the Miridae began in the Permian; most genus‐level radiations within subfamilies began in the late Cretaceous, probably in response to the angiosperm radiation. Ancestral feeding state reconstructions based on Bayesian and parsimony inference were largely congruent and both reconstructed phytophagy as the ancestral state of the Miridae. Furthermore, the feeding habits of the common ancestors of Mirinae + Deraeocorinae, Bryocorinae + Cylapinae + Isometopinae + Orthotylinae, and the remaining taxa excluding Phylinae, were inferred as phytophagous. Therefore, at least three shifts from phytophagy or polyphagy to predation occurred within the Miridae. Additionally, based on the mirid host‐plant records, we discovered several trends, such as a strong relationship between host‐plant ranges and a facultative feeding habit. © The Willi Hennig Society 2011.     

Phylogeny of pholcid spiders (Araneae: Pholcidae): combined analysis using morphology and molecules

The spider family Pholcidae comprises a large number of mainly tropical, web-weaving spiders, and is among the most diverse and dominant spider groups in the world. The phylogeny of this family has so far been investigated exclusively using morphological data. Here, we present the first molecular data for the family analyzed in a phylogenetic context. Four different gene regions (12S rRNA, 16S rRNA, cytochrome c oxidase subunit I, 28S rRNA) and 45 morphological characters were scored for 31 pholcid and three outgroup taxa. The data were analyzed both for individual genes, combined molecular data, and molecular plus morphological data, using parsimony, maximum likelihood, and Bayesian methods. Some of the phylogenetic hypotheses obtained previously using morphology alone were also supported by our results, like the monophyly of pholcines and of the New World clade. On the other hand, some of the previous hypotheses could be discarded with some confidence (monophyly of holocnemines, the position of Priscula), and still others need further investigation (the position of holocnemines, ninetines, and Metagonia). The data obtained provide an excellent basis for future investigations of phylogenetic patterns both within the family and among spider families.     

5S rRNA sequences of 12 species of flatworms: implications for the phylogeny of the Platyhelminthes

5S rRNAs from 12 species of free living and parasitic platyhelminthes were sequenced. In the phylogenetic analysis, attention was focused on the statistical estimates of the trees corresponding to existing phylogenetic hypotheses. The available 5S rRNA data agree well with widely accepted views on the relationships between the Acoela, Polycladida, Tricladida, and Neorhabdocoela; our analysis of the published 18S rRNA sequences also demonstrated good correspondence between these views and molecular data. With available 5S rRNA data the hypothesis that the dalyellioid turbellarians is the sister group of the Neodermata is less convincing than the hypotheses proposing the Neodermata as the sister group of the Neorhabdocoela, or of the Seriata, or of the branch uniting them. A relatively low rate of base replacement in parasitic flatworms, probably, accounts for the uncertain position of the Neodermata, while a relatively high rate in planarians may explain a relatively too early divergence of the Tricladida in several published phylogenetic trees constructed from various rRNA data.     

Comparative morphology of cercal structures in true crickets and their allies (Orthoptera, Ensifera): a phylogenetic perspective

 Cercal structures are surveyed in a large number of crickets sensu lato (Orthoptera, Ensifera, Gryllidea) to analyse their diversity and check for their potential phylogenetic interest. Several other Ensifera are also examined for outgroup comparisons. The main results indicate that Gryllidea can be characterised by several features of their cerci, namely the irregular alignment and the varied size of club-shaped setae. Peculiar features of cercal structures may also be autapomorphic of Gryllidea subclades, such as the presence of wedges on the surface of club-shaped setae (Grylloidea, Gryllotalpidae), the presence of scale-like setae (Mogoplistidae) or that of apical pores on trichoid setae (Myrmecophilidae, Myrmecophilinae), for example. At the scale of Ensifera, three characters are of phylogenetic interest: the presence of club-shaped setae in Gryllidea and Stenopelmatidae, the presence of inner rims inside the sockets of filiform and, when present, club-shaped setae in Gryllidea and, if confirmed, in Rhaphidophoridae, and the occurrence of microtrichiae on the cerci surface in Gryllidea and Rhaphidophoridae. Accepted: 4 October 1998     

Are the Platyhelminthes a monophyletic primitive group? An assessment using 18S rDNA sequences

In most zoological textbooks, Platyhelminthes are depicted as an early- emerging clade forming the likely sister group of all the other Bilateria. Other phylogenetic proposals see them either as the sister group of most of the Protostomia or as a group derived from protostome coelomate ancestors by progenesis. The main difficulty in their correct phylogenetic placing is the lack of convincing synapomorphies for all Platyhelminthes, which may indicate that they are polyphyletic. Moreover, their internal phylogenetic relationships are still uncertain. To test these hypotheses, new complete 18S rDNA sequences from 13 species of "Turbellaria" have been obtained and compared to published sequences of 2 other "Turbellaria," 3 species of parasitic Platyhelminthes, and several diploblastic and deuterostome and protostome triploblastics. Maximum-parsimony, maximum-likelihood, and neighbor-joining methods were used to infer their phylogeny. The results show the order Catenulida to form an independent early- branching clade and emerge as a potential sister group of the rest of the Bilateria, while the rest of Platyhelminthes (Rhabditophora), which includes the parasites, form a clear monophyletic group closely related to the protostomes. The order Acoela, morphologically considered as candidates to be ancestral, are shown to be fast-clock organisms for the 18S rDNA gene. Hence, long-branching of acoels and insufficient sampling of catenulids and acoels leave their position still unresolved and call for further studies. Within the Rhabditophora, our analyses suggest (1) a close relationship between orders Macrostomida and Polycladida, forming a clear sister group to the rest of orders; (2) that parasitic platyhelminthes appeared early in the evolution of the group and form a sister group to a still-unresolved clade made by Nemertodermatida, Lecithoepitheliata, Prolecithophora, Proseriata, Tricladida, and Rhabdocoela; and (3) that Seriata is paraphyletic.      

Phylogenetic relationships of the pipid frogs Xenopus and Silurana: an integration of ribosomal DNA and morphology

Relationships of the pipid frog genus Silurana (= Xenopus tropicalis group of some authors) are of particular interest to developmental and molecular biologists because of the purported ancestral (i.e., unduplicated) karyotype of S. tropicalis relative to the genus Xenopus. Although most previous studies have assumed that Silurana is the sister group of Xenopus, recent morphological work suggests that Silurana is more closely related both to the South American genus Pipa and to the African genera Hymenochirus and Pseudhymenochirus than it is to Xenopus. We examined 1,486 bp of relatively variable regions of the ribosomal DNA array (including portions of the 18S and 28S genes, as well as part of an internal transcribed spacer) in Hymenochirus, Silurana, and Xenopus, as well as the outgroup genus Spea, in order to test the alternative hypotheses of relationships for Silurana. Maximum-parsimony analysis using bootstrapping and an analysis using Lake's method of invariants both significantly support the sister-group relationship between Xenopus and Silurana rather than the relationship suggested by morphology. Analysis of the combined morphological/molecular data matrix also significantly supports the Xenopus-Silurana relationship. Although our results are not inconsistent with the recognition of the genus Silurana to accommodate the species formerly called X. tropicalis and X. epitropicalis, the proposed relationships do not require the recognition of this genus in order to render Xenopus monophyletic.     

Phylogenetic relationships of salangid fishes (Osmeridae, Salanginae) with comments on phylogenetic placement of the salangids based on mitochondrial DNA sequences

We used partial DNA sequences of cytochrome b and 16S mitochondrial genes to determine the phylogenetic placement of salangid fishes and the generic relationships within the salangids. Our molecular data strongly support the monophyly of salangid fishes, the inclusion of salangids in the Osmeridae, and the sister group relationship between salangids and osmerids. Our analyses suggest that Plecoglossus can be separated from all the other salangids and osmerids. Mallotus and Hypomesus are clustered within Osmerinae, rather than allied with Salanginae. As regards the relationships within the salangids, our analyses are incongruent with all previous classification hypotheses. Our phylogenetic analyses support the sister group relationships between Protosalanx and Neosalanx, and between Salanx and Hemisalanx. More evidences show that Leucosoma is more closely related to the Salanx-Hemisalanx clade, while Salangichthys forms part of an unresolved basal polytomy.     

Molecular phylogeny of the stromateoid fishes (Teleostei: Perciformes) inferred from mitochondrial DNA sequences and compared with morphology-based hypotheses

The phylogenetic relationships among 21 species of stromateoid fishes, representing five families and 13 genera, were reconstructed using 3263bp of mitochondrial DNA sequences, including the posterior half of the 16S rRNA and entire COI and Cytb genes. The resultant molecular phylogenies were compared with previous phylogenetic hypotheses inferred from morphological characters. Molecular phylogenetic trees were constructed using the maximum parsimony, maximum likelihood, and Bayesian methods. All three methods resulted in well-resolved trees with most nodes being supported by moderate to high support values. In contrast to previous morphological analyses, which resulted in non-monophyly of Centrolophidae, all three methods utilized for the present molecular analyses supported the monophyly of Centrolophidae, as well as the reciprocal monophyly of the other stromateoid families, previous morphological hypotheses being rejected by the Templeton and Shimodaira-Hasegawa tests. In addition, the three methods indicated a sister-group relationship between Ariommatidae and Nomeidae. The position of Tetragonuridae was, however, incongruent between the MP method and the ML and Bayesian methods, being placed in the most basal position of Stromateoidei in the former, but occupying a sister relationship to Stromateidae in the latter. Comparison of the molecular phylogenies to previous morphological hypotheses suggested that evolutionary changes in morphological characters have not occurred equally among the stromateoid lineages, the evolution of the centrolophids not having been accompanied by appreciable morphological changes, whereas other stromateoids have undergone considerable morphological changes during their evolutionary history. The molecular phylogenies also shed some light on the evolutionary pattern of the pharyngeal sac, two of the four types of sac corresponding to two main lineages of Stromateoidei. Some taxonomic implications were also discussed.