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1.
In this study, we successfully assembled the complete mitochondrial genome of the Amu Darya sturgeon Pseudoscaphirhynchus kaufmanni. Based on this mitochondrial genome and previously published mitochondrial genomes of members of the Acipenseridae family, we assessed the phylogenetic position of P. kaufmanni using maximum likelihood and Bayesian inference for phylogeny reconstruction. The resultant phylogenetic trees were well-resolved, with congruence between different phylogenetic methods. This robust phylogenetic analysis elucidated the relationship among the four acipenserid genera and strongly supported the division of the family into three main clades. Evaluation of molecular phylogeny using maximum likelihood and Bayesian analysis led to the following conclusions: (a) the most basal position within the Acipenseridae remains in the clade containing Acipenser oxyrinchus and Acipenser sturio; (b) the genus Scaphirhynchus belongs to the Atlantic clade and is a sister group of the remaining species of the clade; and (c) the close relationship between P. kaufmanni and Acipenser stellatus is well supported.  相似文献   

2.
Abstract.  In this study, we assessed the ability of mitochondrial genome sequences to recover a test phylogeny of five hymenopteran taxa from which phylogenetic relationships are well accepted. Our analyses indicated that the test phylogeny was well recovered in all nucleotide Bayesian analyses when all the available holometabolan (i.e. outgroup) taxa were included, but only in Bayesian analyses excluding third codon positions when only the hymenopteran representatives and a single outgroup were included. This result suggests that taxon sampling of the outgroup might be as important as taxon sampling of the ingroup when recovering hymenopteran phylogenetic relationships using whole mitochondrial genomes. Parsimony analyses were more sensitive to both taxon sampling and the analytical model than Bayesian analyses, and analyses using the protein dataset did not recover the test phylogeny. In general, mitochondrial genomes did not resolve the position of the Hymenoptera within the Holometabola with confidence, suggesting that an increased taxon sampling, both within the Holometabola and among outgroups, is necessary.  相似文献   

3.
The phylogenetic relationships within the fungus gnat tribe Exechiini have been left unattended for many years. Recent studies have not shed much light on the intergeneric relationship within the tribe. Here the first attempt to resolve the phylogeny of the tribe Exechiini using molecular markers is presented. The nuclear 18S and the mitochondrial 16S, and cytochrome oxidase subunit I (COI) genes were successfully sequenced for 20 species representing 15 Exechiini genera and five outgroup genera. Bayesian, maximum parsimony and maximum likelihood analyses revealed basically congruent tree topologies and the monophyly of Exechiini, including the genus Cordyla , is confirmed. The molecular data corroborate previous morphological studies in several aspects. Cordyla is found in a basal clade together with Brachypeza , Pseudorymosia and Stigmatomeria . The splitting of the genera Allodiopsis s.l. and Brevicornu s.l. as well as the sistergroup relationship of Exechia and Exechiopsis is also supported. The limited phylogenetic information provided by morphological characters is mirrored in the limited resolution of the molecular markers used in this study. Short internal and long-terminal branches obtained may indicate a rapid radiation of the Exechiini genera during a short evolutionary period.  相似文献   

4.
Phylogenetic relationships within the family Alestidae were investigated using parsimony, maximum likelihood, and Bayesian approaches based on a molecular dataset that included both nuclear and mitochondrial markers. Multiple representatives of all but two of the recognized alestid genera were included, which allowed for testing previous hypotheses of intergeneric relationships and the monophyly of several genera. The phylogenetic position of the Neotropical genus Chalceus with respect to the family Alestidae was also examined. In order to understand the temporal context of alestid diversification, Bayesian methods of divergence time estimation using fossil data in the form of calibration priors were used to date the nodes of the phylogenetic tree. Our results rejected the monophyly of the family as currently recognized (Alestidae sensu lato) and revealed several instances of poly- and paraphyly among genera. The genus Chalceus was recovered well nested within Neotropical characiforms, thus rejecting the hypothesis that this taxon is the most basal alestid. The estimated mean divergence time for the alestid clade (Alestidae sensu stricto) was 54 Mya with a 95% credibility interval of 63-49 Mya. These results are incongruent with the hypothesis that the origin of the family Alestidae predates the African-South American Drift-Vicariance event.  相似文献   

5.
The Hylobatidae (gibbons) are among the most endangered primates and their evolutionary history and systematics remain largely unresolved. We have investigated the species-level phylogenetic relationships among hylobatids using 1257 bases representing all species and an expanded data set of up to 2243 bases for select species from the mitochondrial ND3-ND4 region. Sequences were obtained from 34 individuals originating from all 12 recognized extant gibbon species. These data strongly support each of the four previously recognized clades or genera of gibbons, Nomascus, Bunopithecus, Symphalangus, and Hylobates, as monophyletic groups. Among these clades, there is some support for either Bunopithecus or Nomascus as the most basal, while in all analyses Hylobates appears to be the most recently derived. Within Nomascus, Nomascus sp. cf. nasutus is the most basal, followed by N. concolor, and then a clade of N. leucogenys and N. gabriellae. Within Hylobates, H. pileatus is the most basal, while H. moloch and H. klossii clearly, and H. agilis and H. muelleri likely form two more derived monophyletic clades. The segregation of H. klossii from other Hylobates species is not supported by this study. The present data are (1) consistent with the division of Hylobatidae into four distinct clades, (2) provide the first genetic evidence for all the species relationships within Nomascus, and (3) call for a revision of the current relationships among the species within Hylobates. We propose a phylogenetic tree as a working hypothesis against which intergeneric and interspecific relationships can be tested with additional genetic, morphological, and behavioral data.  相似文献   

6.
Euastacus crayfish are endemic to freshwater ecosystems of the eastern coast of Australia. While recent evolutionary studies have focused on a few of these species, here we provide a comprehensive phylogenetic estimate of relationships among the species within the genus. We sequenced three mitochondrial gene regions (COI, 16S, and 12S) and one nuclear region (28S) from 40 species of the genus Euastacus, as well as one undescribed species. Using these data, we estimated the phylogenetic relationships within the genus using maximum-likelihood, parsimony, and Bayesian Markov Chain Monte Carlo analyses. Using Bayes factors to test different model hypotheses, we found that the best phylogeny supports monophyletic groupings of all but two recognized species and suggests a widespread ancestor that diverged by vicariance. We also show that Euastacus and Astacopsis are most likely monophyletic sister genera. We use the resulting phylogeny as a framework to test biogeographic hypotheses relating to the diversification of the genus.  相似文献   

7.
A phylogenetic analysis of the sugeonfish family Acanthuridae was conducted to investigate: (a) the pattern of divergences among outgroup and basal ingroup taxa, (b) the pattern of species divergences within acanthurid genera, (c) monophyly in the genus Acanthurus, and (d) the evolution of thick-walled stomach morphology in the genera Acanthurus and Ctenochaetus. Fragments of the 12S, 16S, t-Pro, and control region mitochondrial genes were sequenced for 21 acanthurid taxa (representing all extant genera) and four outgroup taxa. Unweighted parsimony analysis produced two optimal trees. Both of these were highly incongruent with a previous morphological phylogeny, especially with regard to the placement of the monotypic outgroups Zanclus and Luvarus. The maximum likelihood tree and the morphological phylogeny were not significantly different and the conflicting branches were very short. Split decomposition analysis identified conflict in the placement of long basal branches separated by short internodes, providing further evidence that long branch attraction is an important cause of disagreement between molecular and morphological trees. Parametric bootstrapping rejected hypotheses of monophyly of: (a) the genus Acanthurus and (b) a group containing representatives of Acanthurus/Ctenochaetus with thick-walled stomachs. The branching pattern of the likelihood and split decomposition trees indicates that evolution in the acanthurid clade has involved at least three periods of intense speciation.  相似文献   

8.
The leaf beetle genus Trirhabda contains 26 described species from the United States and Canada, feeding on host plants from the families Asteraceae and Hydrophyllaceae. In this study, we present a phylogeny for the genus that was reconstructed from mitochondrial COI and 12S rRNA fragments, nuclear ITS2 rRNA, and morphological characters. Both parsimony and mixed-model Bayesian likelihood analyses were performed. Under both methods, the mitochondrial and nuclear partitions support the same backbone phylogeny, as do the combined data. The utility of the molecular data is contrasted with the low phylogenetic signal among morphological characters. The phylogeny was used to trace the evolution of the host-plant association in Trirhabda. The recovered phylogeny shows that although the host-plant association is phylogenetically conservative, Trirhabda experienced one shift to a distantly related host-plant family, 6 shifts between host-plant tribes, and 6 between genera within tribes. The phylogeny reveals that Trirhabda were plesiomorphically adapted to tolerate complex secondary compounds of its host plants and this adaptation is retained in Trirhabda species, as evidenced by multiple shifts from chemically simpler host plants back to the more complex host plants.  相似文献   

9.
Partial sequences of 16S and 12S mitochondrial ribosomal DNA were used to examine the phylogenetic relationships of the primarily eastern Pacific genus Paralabrax (Perciformes: Serranidae) and allied taxa. Paralabrax is considered a basal serranine, which is itself considered the basal subfamily in the Serranidae. Multiple serranines reported closely related to Paralabrax from the genera Serranus, Hypoplectrus, Cratinus, and Centropristis were used as outgroups. Species from the remaining two subfamilies, Epinephilinae and Anthiinae, of the Serranidae were also used in the analyses. The tree of the Serranidae was rooted with the families Polyprionidae and Priacanthidae. Paralabrax, the Serranidae, and the Serraninae were monophyletic in this study. Serranus was found to be paraphyletic. Centropristis, formerly considered the sister taxon to Paralabrax, was not closely related in these analyses. Cratinus agassizii, a monotypic genus from the eastern Pacific, was found to be the sister taxon to Paralabrax. There is greater resolution for intergeneric and subfamily relations than interspecific relationships. A single most parsimonious tree for the interspecific relationships of Paralabrax and allied taxa is proposed. This proposed molecular phylogeny is consistent with known biogeographic processes in the eastern Pacific.  相似文献   

10.
Glass sponges (Class Hexactinellida) are important components of deep-sea ecosystems and are of interest from geological and materials science perspectives. The reconstruction of their phylogeny with molecular data has only recently begun and shows a better agreement with morphology-based systematics than is typical for other sponge groups, likely because of a greater number of informative morphological characters. However, inconsistencies remain that have far-reaching implications for hypotheses about the evolution of their major skeletal construction types (body plans). Furthermore, less than half of all described extant genera have been sampled for molecular systematics, and several taxa important for understanding skeletal evolution are still missing. Increased taxon sampling for molecular phylogenetics of this group is therefore urgently needed. However, due to their remote habitat and often poorly preserved museum material, sequencing all 126 currently recognized extant genera will be difficult to achieve. Utilizing morphological data to incorporate unsequenced taxa into an integrative systematics framework therefore holds great promise, but it is unclear which methodological approach best suits this task. Here, we increase the taxon sampling of four previously established molecular markers (18S, 28S, and 16S ribosomal DNA, as well as cytochrome oxidase subunit I) by 12 genera, for the first time including representatives of the order Aulocalycoida and the type genus of Dactylocalycidae, taxa that are key to understanding hexactinellid body plan evolution. Phylogenetic analyses suggest that Aulocalycoida is diphyletic and provide further support for the paraphyly of order Hexactinosida; hence these orders are abolished from the Linnean classification. We further assembled morphological character matrices to integrate so far unsequenced genera into phylogenetic analyses in maximum parsimony (MP), maximum likelihood (ML), Bayesian, and morphology-based binning frameworks. We find that of these four approaches, total-evidence analysis using MP gave the most plausible results concerning congruence with existing phylogenetic and taxonomic hypotheses, whereas the other methods, especially ML and binning, performed more poorly. We use our total-evidence phylogeny of all extant glass sponge genera for ancestral state reconstruction of morphological characters in MP and ML frameworks, gaining new insights into the evolution of major hexactinellid body plans and other characters such as different spicule types. Our study demonstrates how a comprehensive, albeit in some parts provisional, phylogeny of a larger taxon can be achieved with an integrative approach utilizing molecular and morphological data, and how this can be used as a basis for understanding phenotypic evolution. The datasets and associated trees presented here are intended as a resource and starting point for future work on glass sponge evolution.  相似文献   

11.
Molecular phylogenetics and evolution of turtles   总被引:4,自引:0,他引:4  
Turtles are one of Earth's most instantly recognizable life forms, distinguished for over 200 million years in the fossil record. Even so, key nodes in the phylogeny of turtles remain uncertain. To address this issue, we sequenced >90% of the nuclear recombination activase gene 1 (RAG-1) for 24 species representing all modern turtle families. RAG-1 exhibited negligible saturation and base composition bias, and extensive base composition homogeneity. Most of the relationships suggested by prior phylogenetic analyses were also supported by RAG-1 and, for at least two critical nodes, with a much higher level of support. RAG-1 also indicates that the enigmatic Platysternidae and Chelydridae, often considered sister taxa based on morphological evidence, are not closely related, although their precise phylogenetic placement in the turtle tree is still unresolved. Although RAG-1 is phylogenetically informative, our research revealed fundamental conflicts among analytical methods for estimating phylogenetic hypotheses. Maximum parsimony analyses of RAG-1 alone and in combination with two mitochondrial genes suggest the earliest phylogenetic splits separating into three basal branches, the pig-nosed turtles (Carettochelyidae), the softshell turtles (Trionychidae), and a clade comprising all remaining extant turtles. Maximum likelihood and Bayesian analyses group Carettochelyidae and Trionychidae (=Trionychoidae) in their more traditional location as the sister taxon to all other hidden-necked turtles, collectively forming the Cryptodira. Our research highlights the utility of molecular data in identifying issues of character homology in morphological datasets, while shedding valuable light on the biodiversity of a globally imperiled taxon.  相似文献   

12.
The molecular phylogenetics of decapod crustaceans has been based on sequence data from a limited number of genes. These have included rapidly evolving mitochondrial genes, which are most appropriate for studies of closely related species, and slowly evolving nuclear ribosomal RNA genes, which have been most useful for resolution of deep branches within the Decapoda. Here we examine the utility of the nuclear gene that encodes arginine kinase for phylogenetic reconstruction at intermediate levels (relationships among genera and families) within the decapod infraorder Brachyura (the true crabs). Analyses based on arginine kinase sequences were compared and combined with those for the mitochondrial cytochrome oxidase I gene. All of the genera in our taxon sample were resolved with high support with arginine kinase data alone. However, some of these genera were grouped into clades that are in conflict with recognized brachyuran families. A phylogeny based on cytochrome oxidase I was consistent with the arginine kinase phylogeny, but with weaker support. A recently proposed measure of phylogenetic informativeness indicated that arginine kinase was generally more informative than cytochrome oxidase I for relationships above the level of genus. Combined analysis of data from both genes provided strong support for clades that are in conflict with current assignments of genera to the families Epialtidae, Mithracidae, Pisidae, and Portunidae.  相似文献   

13.
To explore phylogenetic relationships among glyptosternoid fishes, we determined nucleotide sequences of the complete mitochondrial cytochrome b gene region (1138 base pair). Thirteen species of glyptosternoid fishes and six species of non-glyptosternoids represent 10 sisorid genera were examined. Molecular phylogenetic trees were constructed using the maximum parsimony, minimum evolution, maximum likelihood, and Bayesian methods. Bayesian and maximum likelihood analyses support the monophyly of glyptosternoids, but our hypothesis of internal relationships differs from previous hypothesis. Results indicated that glyptosternoid is a monophyletic group and genera Glyptosternum and Exostoma are two basal species having a primitive position among it. Genera Euchiloglanis and Pareuchiloglanis form a sister-group. Then they form a sister-group with Pseudexostoma plus Oreoglanis. Our result also found that Pareuchiloglanis anteanalis might be considered as the synonyms of Parechiloglanis sinensis, and genus Euchiloglanis might have only one valid species, Euchiloglanis davidi.  相似文献   

14.
Many phylogenetic analyses that include numerous terminals but few genes show high resolution and branch support for relatively recently diverged clades, but lack of resolution and/or support for "basal" clades of the tree. The various benefits of increased taxon and character sampling have been widely discussed in the literature, albeit primarily based on simulations rather than empirical data. In this study, we used a well-sampled gene-tree analysis (based on 100 mitochondrial genomes of higher teleost fishes) to test empirically the efficiency of different methods of data sampling and phylogenetic inference to "correctly" resolve the basal clades of a tree (based on congruence with the reference tree constructed using all 100 taxa and 7990 characters). By itself, increased character sampling was an inefficient method by which to decrease the likelihood of "incorrect" resolution (i.e., incongruence with the reference tree) for parsimony analyses. Although increased taxon sampling was a powerful approach to alleviate "incorrect" resolution for parsimony analyses, it had the general effect of increasing the number of, and support for, "incorrectly" resolved clades in the Bayesian analyses. For both the parsimony and Bayesian analyses, increased taxon sampling, by itself, was insufficient to help resolve the basal clades, making this sampling strategy ineffective for that purpose. For this empirical study, the most efficient of the six approaches considered to resolve the basal clades when adding nucleotides to a dataset that consists of a single gene sampled for a small, but representative, number of taxa, is to increase character sampling and analyze the characters using the Bayesian method.  相似文献   

15.
The family Microhylidae has a large circumtropic distribution and contains about 400 species in a highly subdivided taxonomy. Relationships among its constituent taxa remained controversial due to homoplasy in morphological characters, resulting in conflicting phylogenetic hypotheses. A phylogeny based on four nuclear genes (rag-1, rag-2, tyrosinase, BDNF) and one mitochondrial gene (CO1) of representatives of all currently recognized subfamilies uncovers a basal polytomy between several subfamilial clades. A sister group relationship between the cophylines and scaphiophrynines is resolved with moderate support, which unites these endemic Malagasy taxa for the first time. The American members of the subfamily Microhylinae are resolved to form a clade entirely separate from the Asian members of that subfamily. Otophryne is excluded from the subfamily Microhylinae, and resolved as a basal taxon. The placement of the Asian dyscophine Calluella nested within the Asian Microhyline clade rather than with the genus Dyscophus is corroborated by our data. Bayesian estimates of the divergence time of extant Microhylidae (47-90 Mya) and among the subclades within the family are discussed in frameworks of alternative possible biogeographic scenarios.  相似文献   

16.
The subfamilies Erinaceinae and Galericinae of the extant family Erinaceidae are the only living representatives of the once diverse taxon Erinaceomorpha. In the present study, we performed the first multilocus analysis of phylogenetic relationships among genera of Erinaceidae and estimated the split times between and within the two subfamilies. The analyses of five nuclear and two mitochondrial genes produced a well‐resolved molecular phylogeny. Generally, the molecular tree is compatible with the morphology‐based taxonomy proposed by Frost, Wozencraft & Hoffmann with the exception of the position of Mesechinus, which is placed as the closest sister taxon of Hemiechinus. Another point of contradiction between molecular and morphological phylogenies is the position of Hylomys megalotis, which was consistently placed as the most basal branch among all gymnures in molecular analyses. Genetic relationships between Erinaceus and Atelerix remain unclear, suggesting a hard trichotomy among these two lineages and Hemiechinus + Paraechinus. Molecular dating suggests an ancient origin of the extant gymnure lineages, which date back to the late Eocene to early Oligocene. The age of the basal split within spiny hedgehogs is relatively recent and corresponds to the Miocene–Pliocene boundary. Possible changes to the erinaceid taxonomy are considered. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 499–519.  相似文献   

17.
The shells of strombid gastropods show a wide variety of forms, ranging from small and fusiform to large and elaborately ornamented with a strongly flared outer lip. Here, we present the first species-level molecular phylogeny for strombids and use the resulting phylogenetic framework to explore relationships between species richness and morphological diversity. We use portions of one nuclear (325 bp of histone H3) and one mitochondrial (640 bp of cytochrome oxidase I, COI) gene to infer relationships within the two most species-rich genera in the Strombidae: Strombus and Lambis. We include 32 species of Strombus, representing 10 of 11 extant subgenera, and 3 of the 9 species of Lambis, representing 2 of 3 extant subgenera. Maximum likelihood and Bayesian analyses of COI and of H3 and COI combined suggest Lambis is nested within a paraphyletic Strombus. Eastern Pacific and western Atlantic species of Strombus form a relatively recent monophyletic radiation within an older, paraphyletic Indo-West Pacific grade. Morphological diversity of subclades scales positively with species richness but does not show evidence of strong phylogenetic constraints.  相似文献   

18.
BrachyorrhosSchlegel, 1826a is a terrestrial-fossorial snake genus endemic to eastern Indonesia that has been assigned to six different families and subfamilies within Colubroidea (advanced snakes) over the past ~200 years. Here we report the first molecular sequences for Brachyorrhos and use them to test the position of the genus within snake phylogeny. Our Bayesian and Maximum Likelihood analyses of three mitochondrial and one nuclear gene strongly resolve Brachyorrhos within the rear-fanged semiaquatic Homalopsidae (Colubroidea), as the sister taxon to all other genera and sampled species.  相似文献   

19.
In this study, the phylogenetic relationships among 13 pangasiids and six schilbids of Thailand were reconstructed based on the almost complete mitochondrial cytochrome b (cyt b), 12S rRNA, tRNA-Val and 16S rRNA, as well as the partial nuclear recombination-activating gene 1 (rag1) sequences by using the maximum likelihood and the Bayesian inference methods of phylogenetic reconstruction. The reconstructed phylogeny based on the concatenated sequence data set recovered Pangasiidae and Schilbidae as reciprocally monophyletic groups. Within Pangasiidae, four major clades were recovered, which according to the cyt b genetic distances can be categorized into four genera: Pangasius, Pseudolais, Helicophagus and Pangasianodon. The genus Pangasianodon was strongly supported as the most basal taxon within pangasiids, whereas Pseudolais + Helicophagus were recovered as a sister group of Pangasius. Within the latter, the giant pangasius Pangasius sanitwongsei was recovered as a sister group of the spot pangasius Pangasius larnaudii, Pangasius krempfi as a sister group of Pangasius nasutus + Pangasius conchophilus and Pangasius polyuranodon as a sister species of Pangasius macronema. Other internal phylogenetic relationships, however, were unresolved. Within Schilbidae, Pseudeutropius was supported as the most basal lineage. Eutropiichthys was recovered as a sister group of Clupisoma. The enigmatic Clupisoma sinense was recognized as more closely related to Laides longibarbis than to Clupisoma prateri. Thus, based on the cyt b genetic distances, a recategorization of C. sinense to the genus Laides is suggested. On the basis of a relaxed clock fossil calibration, the divergence of pangasiids and schilbids was estimated to have occurred 14·93 million years before present (b.p.) during the Miocene epoch. The separation between Pangasiidae and Schilbidae took place c. 13·12 Mb.p. during the early middle Miocene. The estimated divergence time of pangasiids is similar to the age of the calibrated fossil, Cetopangasius chaetobranchus, which was discovered in north-central Thailand. This suggests that the oldest pangasiid ancestor diverged into diverse genera in the area.  相似文献   

20.
Conoesucidae (Trichoptera, Insecta) are restricted to SE Australia, Tasmania and New Zealand. The family includes 42 described species in 12 genera, and each genus is endemic to either New Zealand or Australia. Although monophyly has been previously assumed, no morphological characters have been proposed to represent synapomorphies for the group. We collected molecular data from two mitochondrial genes (16S and cytochrome oxidase I), one nuclear gene (elongation factor 1-α) (2237–2277 bp in total), and 12 morphological characters to produce the first phylogeny of the family. We combined the molecular and morphological characters and performed both a maximum parsimony analysis and a Bayesian analysis to test the monophyly of the family, and to hypothesize the phylogeny among its genera. The parsimony analysis revealed a single most parsimonious tree with Conoesucidae being a monophyletic taxon and sistergroup to the Calocidae. The Bayesian inference produced a distribution of trees, the consensus of which is supported with posterior probabilities of 100% for 15 out of 22 possible ingroup clades including the most basal branch of the family, indicating strong support for a monophyletic Conoesucidae. The most parsimonious tree and the tree from the Bayesian analysis were identical except that the ingroup genus Pycnocentria changed position by jumping to a neighbouring clade. Based on the assumption that the ancestral conoesucid species was present on both New Zealand and Australia, a biogeographical analysis using the dispersal-vicariance criteria demonstrated that one or two (depending on which of the two phylogenetic reconstructions were applied) sympatric speciation events took place on New Zealand prior to a single, late dispersal from New Zealand to Australia.  相似文献   

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