| 1. |
- Johansson, Ulf S, et al.
(författare)
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Build-up of the Himalayan avifauna through immigration : A biogeographical analysis of the Phylloscopus and Seicercus warblers
- 2007
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:2, s. 324-333
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Tidskriftsartikel (refereegranskat)abstract
- The Himalayan mountain range is one of the most species-rich areas in the world, harboring about 8% of the world's bird species. In this study, we compare the relative importance of immigration versus in situ speciation to the build-up of the Himalayan avifauna, by evaluating the biogeographic history of the Phylloscopus/Seicercus warblers, a speciose clade that is well represented in Himalayan forests. We use a comprehensive, multigene phylogeny in conjunction with dispersal-vicariance analysis to discern patterns of speciation and dispersal within this clade. The results indicate that virtually no speciation has occurred within the Himalayas. Instead, several speciation events are attributed to dispersal into the Himalayas followed by vicariance between the Himalayas and China/Southeast Asia. Most, perhaps all, of these events appear to be pre-Pleistocene. The apparent lack of speciation within the Himalayas stands in contrast to the mountain-driven Pleistocene speciation suggested for the Andes and the East African mountains.
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| 2. |
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| 3. |
- Alström, Per, Professor, et al.
(författare)
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Phylogeny and classification of the avian superfamily Sylvioidea
- 2006
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Ingår i: Molecular Phylogenetics and Evolution. - Swedish Museum Nat Hist, Dept Vertebrate Zool, SE-10405 Stockholm, Sweden. Swedish Museum Nat Hist, Mol Systemat Lab, SE-10405 Stockholm, Sweden. Uppsala Univ, Evolutionary Biol Ctr, Dept Systemat Zool, SE-75236 Uppsala, Sweden. Univ Gothenburg, Dept Zool, SE-40530 Gothenburg, Sweden. : Elsevier BV. - 1055-7903 .- 1095-9513. ; 38:2, s. 381-397
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Tidskriftsartikel (refereegranskat)abstract
- Sylvioidea is one of the three superfamilies recognized within the largest avian radiation, the parvorder Passerida. In the present study, which is the first taxon-dense analysis of the Sylvioidea based on sequence data (nuclear myoglobin intron II and mitochondrial cytochrome b gene), we investigate the interrelationships among the four "sylvioid" clades found by previous workers, as well as the relationships within the largest of these clades. The nuclear and mitochondrial loci estimate basically the same phylogeny, with minor differences in resolution. The trees based on myoglobin and the combined data identify a strongly supported clade that includes the taxa previously allocated to Sylvioidea, except for Sitta (nuthatches), Certhia (treecreepers), Parus (tits), Remiz (penduline tits), Troglodytes and Campylorhynchus (wrens), Polioptila (gnatcatchers), and Regulus (crests/kinglets); this clade also comprises larks, which have previously been placed in the superfamily Passeroidea. We refer to this clade as Sylvioidea. This clade is further divided into 10 main, well-supported clades, which we suggest form the basis for a revised classification. (c) 2005 Elsevier Inc. All rights reserved.
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| 4. |
- Olsson, Urban, 1954, et al.
(författare)
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Non-monophyletic taxa and cryptic species - Evidence from a molecular phylogeny of leaf-warblers (Phylloscopus, Aves)
- 2005
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Ingår i: Molecular Phylogenetics and Evolution. - Univ Gothenburg, Dept Zool, SE-40530 Gothenburg, Sweden. Uppsala Univ, Evolutionary Biol Ctr, Dept Systemat Zool, SE-75236 Uppsala, Sweden. Swedish Museum Nat Hist, Dept Vertebrate Zool, SE-10405 Stockholm, Sweden. Swedish Museum Nat Hist, Mol Systemat Lab, SE-10405 Stockholm, Sweden. : Elsevier BV. - 1055-7903 .- 1095-9513. ; 36:2, s. 261-276
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Tidskriftsartikel (refereegranskat)abstract
- The avian taxa Cryptigata and Aeanthopneuste have been treated either as subgenera within Phylloscopus (leaf-warblers), or as a distinct genus and an informal group, respectively. The circumscriptions of these taxa have varied between authors. We estimated the phylogeny, based on the mitochondrial cytochrome b and 12S genes and the nuclear myoglobin intron 11, of all except two of the species placed in the Cryptigata and Acanthopneuste groups, as well as two recently described species and representatives of all subgenera and major clades in Phylloscopus and Seicercus recognized by previous studies. Neither Cryptigata nor Acanthopneuste is found to be monophyletic. The polytypic species P. reguloides and P. davisoni show deep divergences between some of their respective subspecies, and the latter species is non-monophyletic. We propose that the former be split into three species and the latter into two species. Seicercus xanthoschistos is nested in a clade that includes only Phylloscopus, and we recommend that it be placed in Phylloscopus. The rate of morphological divergence varies considerably among the taxa in this study. Our results emphasize the importance of dense taxon sampling in intrageneric phylogenetic studies. (c) 2005 Elsevier Inc. All rights reserved.
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| 5. |
- Olsson, Urban, 1954, et al.
(författare)
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Phylogeography of Indonesian and Sino-Himalayan region bush warblers (Cettia, Aves)
- 2006
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 41:3, s. 556-565
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Tidskriftsartikel (refereegranskat)abstract
- We present a hypothesis for the phylogeny and phylogeography of a group of bush warblers in the genus Cettia, based on parts of the mitochondrial Cytochrome b gene and the nuclear myoglobin intron II (in all similar to 1.7 kb). Ancestral areas were reconstructed by dispersal-vicariance analysis and constrained Bayesian inference. The results suggest that the insular taxa in the Cettia vulcania group are most closely related to Cettia flavolivacea, and originated from a dispersal by an ancestral population in the Himalayas towards the south, to the Sunda region. From this population, a second dispersal along a different route colonized China and northern Vietnam. Hence, the Chinese taxon intricata and Vietnamese oblita, currently allocated to C. flavoliuacea, are more closely related to the vulcania group than to the other taxa in the flavolivacea group, and we propose that they be treated as conspecific with C vulcania, restricting C. flavolivacea to Myanmar and the Himalayas.
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| 6. |
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| 7. |
- Alström, Per, et al.
(författare)
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Phylogeny and classification of the Old World Emberizini (Aves, Passeriformes)
- 2008
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 47:3, s. 960-973
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Tidskriftsartikel (refereegranskat)abstract
- The phylogeny of the avian genus Emberiza and the monotypic genera Latoucheornis, Melophus and Miliaria (collectively the Old World Emberizini), as well as representatives for the New World Emberizini, the circumpolar genera Calcarius and Plectrophertax and the four other generally recognized tribes in the subfamily Emberizinae was estimated based on the mitochondrial cytochrome b gene and introns 6-7 of the nuclear ornithine decarboxylase (ODC) gene. Our results support monophyly of the Old World Emberizini, but do not corroborate a sister relationship to the New World Emberizini. Calcarius and Plectrophenax form a clade separated from the other Emberizini. This agrees with previous studies, and we recommend the use of the name Calcariini. Latoucheornis, Melophus and Miliaria are nested within Emberiza, and we therefore propose they be synonymized with Emberiza. Emberiza is divided into four main clades, whose relative positions are uncertain, although a sister relation between a clade with six African species and one comprising the rest of the species (30, all Palearctic) is most likely. Most clades agree with traditional, morphology-based, classifications. However, four sister relationships within Emberiza, three of which involve the previously recognized Latoucheornis, Melophus and Miliaria, are unpredicted, and reveal cases of strong morphological divergence. In contrast, the plumage similarity between adult male Emberiza (formerly Latoucheornis) siemsseni and the nominate subspecies of the New World Junco hyemalis is shown to be the result of parallel evolution. A further case of parallel plumage evolution, between African and Eurasian taxa, is pointed out. Two cases of discordance between the mitochondrial and nuclear data with respect to branch lengths and genetic divergences are considered to be the result of introgressive hybridization.
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| 8. |
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| 9. |
- Alström, Per, et al.
(författare)
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Species delimitation based on multiple criteria : the Spotted Bush Warbler Bradypterus thoracicus complex (Aves : Megaluridae)
- 2008
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Ingår i: Zoological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4082 .- 1096-3642. ; 154:2, s. 291-307
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the importance of using multiple criteria in species delimitations, whatever the conceptual base for species delimitation. We do this by studying plumage, biometrics, egg coloration, song, mitochondrial DNA and habitat/altitudinal distribution in the Spotted Bush Warbler Bradypterus thoracicus (Blyth) complex, and by conducting playback experiments. Taxa that we suggest are best treated as separate species [B. thoracicus (Blyth), B. davidi (La Touche) and B. kashmirensis (Sushkin)] differ in most or all of these aspects, particularly in song and mitochondrial DNA, while those that we treat as subspecies (suschkini) or synonyms (przevalskii) differ slightly and only in morphology.
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| 10. |
- Bachmann, L., et al.
(författare)
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Systematics and biodiversity research in the era of genomics
- 2016
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Ingår i: Zoologica Scripta. - : Wiley. - 0300-3256 .- 1463-6409. ; 45, s. 3-4
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Tidskriftsartikel (refereegranskat)abstract
- On 5 November 2015, The Norwegian Academy of Sciences and Letters (DNVA) and the editors of the Zoologica Scripta invited to the one-day symposium ‘Systematics and Biodiversity Research in the Era of Genomics’. Some 80 scientists gathered at the premises of the DNVA in Oslo, Norway, to explore and discuss the current trends and future developments in the field of Animal Systematics. © 2016 The Authors. Zoologica Scripta published by John Wiley & Sons Ltd on behalf of Royal Swedish Academy of Sciences.
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| 11. |
- Bachmann, L., et al.
(författare)
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The role of systematics for understanding ecosystem functions: Proceedings of the Zoologica Scripta Symposium, Oslo, Norway, 25 August 2022
- 2023
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Ingår i: Zoologica Scripta. - : Wiley. - 0300-3256 .- 1463-6409. ; 52:3, s. 187-214
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Tidskriftsartikel (refereegranskat)abstract
- On 25 August 2022, the Zoologica Scripta - An International Journal of Systematic Zoology and the Norwegian Academy of Sciences and Letters arranged a symposium entitled 'The role of systematics for understanding ecosystem functions' in the Academy's premises in Oslo, Norway. The symposium aimed at offering a forum for exploring and discussing trends and future developments in the field of systematics. Eleven international experts contributed expertise on various issues related to global challenges, such as biodiversity assessments, databases, cutting-edge analysis tools, and the consequences of the taxonomic impediment. Here, we compiled a multi-author proceedings paper of the symposium contributions that are arranged in chapters and presents the content and the key conclusions of the majority of the presentations.
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| 12. |
- Olsson, Urban, 1954, et al.
(författare)
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Non-monophyly of the avian genus Seicercus (Aves : Sylviidae) revealed by mitochondrial DNA
- 2004
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Ingår i: Zoologica Scripta. - Gothenburg Univ, Dept Zool, SE-40530 Gothenburg, Sweden. Uppsala Univ, Evolutionary Biol Ctr, Dept Systemat Zool, SE-75236 Uppsala, Sweden. : Wiley. - 0300-3256 .- 1463-6409. ; 33:6, s. 501-510
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Tidskriftsartikel (refereegranskat)abstract
- The phylogeny of all species and nearly all subspecies of Seicercus and representatives of all subgenera in Phylloscopus was estimated based on two mitochondrial genes. According to the gene tree, and supported by non-molecular data, Seicercus belongs in three separate clades. Two of these include only taxa currently classified as Seicercus, while the third comprises S. xanthoschistos and P. occipitalis. These results suggest that both Seicercus and Phylloscopus are paraphyletic. The gene tree suggests two more cases of non-monophyly: (1) the 'S. burkii complex' is separated into two different clades, one of which also includes S. affinis and S. poliogenys; (2) two populations of S. affinis intermedius are more closely related to S. affinis ocularis than to a third population of intermedius. A recent proposal to split the 'S. burkii complex' into six species is corroborated, as is the recognition of the taxon cognitus as a colour morph of S. affinis intermedius. Our study also revealed unexpectedly large genetic divergences between three different populations of the monotypic S. poliogenys, indicating the presence of cryptic species. Our results underscore the importance of dense sampling at the specific and infraspecific levels in intrageneric phylogenetic studies.
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| 13. |
- Olsson, Urban, 1954, et al.
(författare)
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The Lanius excubitor (Aves, Passeriformes) conundrum – Taxonomic dilemma when molecular and non-molecular data tell different stories.
- 2010
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 55:2, s. 347-357
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Tidskriftsartikel (refereegranskat)abstract
- The phylogeny of 18 taxa in the Lanius excubitor complex, and the related species L. sphenocercus, L. ludovicianus and L. somalicus, was estimated based on the mitochondrial cytochrome b gene and the non-coding D-loop (in total ∼1.3 kb). According to the mitochondrial gene tree, Lanius excubitor s.l. is non-monophyletic, with some of its subspecies being more closely related to L. sphenocercus, L. ludovicianus, and L. somalicus. Also the division of the L. excubitor complex into a northern (L. excubitor) and a southern (L. meridionalis) species, as has been proposed based on morphological and ecological similarity and geographical distributions, is not compatible with the mitochondrial tree. Overall, genetic divergences among the ingroup taxa are small, indicating a recent radiation. A tree based on the nuclear ornithine decarboxylase (ODC) introns 6–7 is unresolved with respect to the ingroup, but provides strong support for a clade containing the Lanius excubitor complex, L. sphenocercus, L. ludovicianus and L. somalicus. We discuss the incongruence between the current taxonomy and the mitochondrial gene tree, and conclude that based on the latter the Lanius excubitor complex may be treated as at least six species, L. borealis, L. elegans, L. excubitor, L. lahtora, L. meridionalis, and L. uncinatus, but that other taxonomic treatments are also possible. However, uncertainty regarding to which extent the mitochondrial gene tree reflects the species phylogeny prevents us from recommending taxonomic change without further investigation. This study highlights the possible danger of relying on a single molecular marker, such as mitochondrial DNA, in taxonomic revisions and phylogenetic inference
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| 14. |
- Polovodova Asteman, Irina, 1980, et al.
(författare)
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Spreading of an alien benthic foraminifer in the North Sea: a reason to be worried?
- 2023
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Ingår i: International Congress FORAMS2023, Perugia, Italy, 25-30th June. - Perugia, Italy : Micropress Europe & The Grzybowski Foundation.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the Skagerrak-Kattegat (eastern North Sea), the alien benthic foraminifer Nonionella sp. T1 (previously referred to as “Nonionella stella”) was reported for the first time in 2011 and 2012 in the Swedish and southern Norwegian fjords, respectively. Based on dated sediment cores its first occurrence can be traced back to the 1980s in the Gullmar Fjord, to the 2000s in the Öresund and to 2010 in the Oslofjord. Since then, Nonionella sp T1 has spread all over the Kattegat and coastal Skagerrak, according to sampling campaigns performed between 2016 and 2022. The species is now highly abundant in the entire Kattegat, including the Öresund, as well as in fjord mouths of the seasonally hypoxic Gullmar Fjord, the oxic Hakefjord and the long-term polluted Idefjord as demonstrated by molecular and morphospecies data. At the same time, Nonionella sp T1 is rare to absent in the Baltic Sea, Skagerrak deep basin and in deep fjords of western and northern Norway. This study shows some preliminary results on the species’ present distribution in the study area and raises questions about the driving factors and potential effects on the local biodiversity.
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| 15. |
- Alfaya, J. E. F., et al.
(författare)
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DNA barcoding supports identification of Malacobdella species (Nemertea: Hoplonemertea)
- 2015
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Ingår i: Zoological Studies. - : Springer Science and Business Media LLC. - 1021-5506 .- 1810-522X. ; 54
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Tidskriftsartikel (refereegranskat)abstract
- Background: Nemerteans of the genus Malacobdella live inside of the mantle cavity of marine bivalves. The genus currently contains only six species, five of which are host-specific and usually found in a single host species, while the sixth species, M. grossa, has a wide host range and has been found in 27 different bivalve species to date. The main challenge of Malacobdella species identification resides in the similarity of the external morphology between species (terminal sucker, gut undulations number, anus position and gonad colouration), and thus, the illustrations provided in the original descriptions do not allow reliable identification. In this article, we analyse the relationships among three species of Malacobdella: M. arrokeana, M. japonica and M. grossa, adding new data for the M. grossa and reporting the first for M. japonica, analysing 658 base pairs of the mitochondrial cytochrome c oxidase subunit I gene (COI). Based on these analyses, we present and discuss the potential of DNA barcoding for Malacobdella species identification. Results: Sixty-four DNA barcoding fragments of the mitochondrial COI gene from three different Malacobdella species (M. arrokeana, M. japonica and M. grossa) are analysed (24 of them newly sequenced for this study, along with four outgroup specimens) and used to delineate species. Divergences, measured as uncorrected differences, between the three species were M. arrokeana-M. grossa 11.73%, M. arrokeana-M. japonica 10.62% and M. grossa-M. japonica 10.97%. The mean intraspecific divergence within the ingroup species showed a patent gap with respect to the interspecific ones: 0.18% for M. arrokeana, 0.13% for M. grossa and 0.02% for M. japonica (ranges from 0 to 0.91%). Conclusions: We conclude that there is a clear correspondence between the molecular data and distinguishing morphological characters. Our results thus indicate that some morphological characters are useful for species identification and support the potential of DNA barcoding for species identification in a taxonomic group with subtle morphological external differences.
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| 16. |
- Alström, P., et al.
(författare)
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Morphological, vocal and genetic divergence in the Cettia acanthizoides complex (Aves: Cettiidae)
- 2007
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Ingår i: Zoological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4082 .- 1096-3642. ; 149:3, s. 437-452
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Tidskriftsartikel (refereegranskat)abstract
- We used morphological, vocal and molecular (one mitochondrial and two nuclear loci) data to re-evaluate the taxonomic status of the taxa acanthizoides, concolor, and brunnescens in the Cettia acanthizoides (J. Verreaux, 1871) complex. We conclude that all three are valid taxa, and that acanthizoides of China and concolor of Taiwan are best treated as conspecific, whereas brunnescens of the Himalayas is better considered as a separate species. The degree of morphological, vocal, and genetic differentiation is variably congruent among all taxa; the recently separated acanthizoides and concolor differ slightly in plumage and structure but are indistinguishable in vocalizations, whereas the earlier diverged brunnescens and acanthizoides/concolor differ only slightly more in morphology but to a much greater degree in vocalizations. We stress the essential nature of taxonomic revisions as a prerequisite for the biodiversity estimates required for conservation planning.
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| 17. |
- ANDRADE, S.C.S, et al.
(författare)
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A transcriptomic approach to ribbon worm systematics (Nemertea): resolving the Pilidiophora problem.
- 2014
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 31:12, s. 3206-3215
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Tidskriftsartikel (refereegranskat)abstract
- Resolving the deep relationships of ancient animal lineages has proven difficult using standard Sanger-sequencing approaches with a handful of markers. We thus reassess the relatively well-studied phylogeny of the phylum Nemertea (ribbon worms)—for which the targeted gene approaches had resolved many clades but had left key phylogenetic gaps—by using a phylogenomic approach using Illumina-based de novo assembled transcriptomes and automatic orthology prediction methods. The analysis of a concatenated data set of 2,779 genes (411,138 amino acids) with about 78% gene occupancy and a reduced version with 95% gene occupancy, under evolutionary models accounting or not for site-specific amino acid replacement patterns results in a well-supported phylogeny that recovers all major accepted nemertean clades with the monophyly of Heteronemertea, Hoplonemertea, Monostilifera, being well supported. Significantly, all the ambiguous patterns inferred from Sanger-based approaches were resolved, namely the monophyly of Palaeonemertea and Pilidiophora. By testing for possible conflict in the analyzed supermatrix, we observed that concatenation was the best solution, and the results of the analyses should settle prior debates on nemertean phylogeny. The study highlights the importance, feasibility, and completeness of Illumina-based phylogenomic data matrices.
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| 18. |
- Andrade, S. C. S., et al.
(författare)
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Disentangling ribbon worm relationships: multi-locus analysis supports traditional classification of the phylum Nemertea
- 2012
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Ingår i: Cladistics. - : Wiley. - 0748-3007. ; 28:2, s. 141-159
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Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic relationships of selected members of the phylum Nemertea are explored by means of six markers amplified from the genomic DNA of freshly collected specimens (the nuclear 18S rRNA and 28S rRNA genes, histones H3 and H4, and the mitochondrial genes 16S rRNA and cytochrome c oxidase subunit I). These include all previous markers and regions used in earlier phylogenetic analyses of nemerteans, therefore acting as a scaffold to which one could pinpoint any previously published study. Our results, based on analyses of static and dynamic homology concepts under probabilistic and parsimony frameworks, agree in the non-monophyly of Palaeonemertea and in the monophyly of Heteronemerta and Hoplonemertea. The position of Hubrechtella and the Pilidiophora hypothesis are, however, sensitive to analytical method, as is the monophyly of the non-hubrechtiid palaeonemerteans. Our results are, however, consistent with the main division of Hoplonemertea into Polystilifera and Monostilifera, the last named being divided into Cratenemertea and Distromatonemertea, as well as into the main division of Heteronemertea into Baseodiscus and the remaining species. The study also continues to highlight the deficient taxonomy at the family and generic level within Nemertea and sheds light on the areas of the tree that require further refinement.
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| 19. |
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| 20. |
- Andre, C., et al.
(författare)
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Species identification of bivalve larvae using random amplified polymorphic DNA (RAPD): differentiation between Cerastoderma edule and C-lamarcki
- 1999
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Ingår i: Journal of the Marine Biological Association of the United Kingdom. - 0025-3154. ; 79:3, s. 563-565
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Tidskriftsartikel (refereegranskat)abstract
- The polymerase chain reaction (PCR) was used to produce species-specific DNA markers (RAPDs) from two sibling cockle species and five other co-occurring intertidal bivalves. Amplification reactions with one single primer readily distinguished larvae and adults of Cerastoderma edule from larvae and adults of C. lamarcki, and from adults of Mya arenaria Macoma balthica, Scrobicularia plana, Venerupis pulastra and Mytilus edulis. Random amplified polymorphic DNA (RAPD) is suggested as a simple and quick method to determine species identity in taxa that are difficult to identify on the basis of morphological characters alone, such as marine bivalve larvae.
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| 21. |
- Chen, Hai-Xia, et al.
(författare)
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A comparative study of nemertean complete mitochondrial genomes, including two new ones for Nectonemertes cf. mirabilis and Zygeupolia rubens, may elucidate the fundamental pattern for the phylum Nemertea
- 2012
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Ingår i: Bmc Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: The mitochondrial genome is important for studying genome evolution as well as reconstructing the phylogeny of organisms. Complete mitochondrial genome sequences have been reported for more than 2200 metazoans, mainly vertebrates and arthropods. To date, from a total of about 1275 described nemertean species, only three complete and two partial mitochondrial DNA sequences from nemerteans have been published. Here, we report the entire mitochondrial genomes for two more nemertean species: Nectonemertes cf. mirabilis and Zygeupolia rubens. Results: The sizes of the entire mitochondrial genomes are 15365 bp for N. cf. mirabilis and 15513 bp for Z. rubens. Each circular genome contains 37 genes and an AT-rich non-coding region, and overall nucleotide composition is AT-rich. In both species, there is significant strand asymmetry in the distribution of nucleotides, with the coding strand being richer in T than A and in G than C. The AT-rich non-coding regions of the two genomes have some repeat sequences and stem-loop structures, both of which may be associated with the initiation of replication or transcription. The 22 tRNAs show variable substitution patterns in nemerteans, with higher sequence conservation in genes located on the H strand. Gene arrangement of N. cf. mirabilis is identical to that of Paranemertes cf. peregrina, both of which are Hoplonemertea, while that of Z. rubens is the same as in Lineus viridis, both of which are Heteronemertea. Comparison of the gene arrangements and phylogenomic analysis based on concatenated nucleotide sequences of the 12 mitochondrial protein-coding genes revealed that species with closer relationships share more identical gene blocks. Conclusion: The two new mitochondrial genomes share many features, including gene contents, with other known nemertean mitochondrial genomes. The tRNA families display a composite substitution pathway. Gene order comparison to the proposed ground pattern of Bilateria and some lophotrochozoans suggests that the nemertean ancestral mitochondrial gene order most closely resembles the heteronemertean type. Phylogenetic analysis proposes a sister-group relationship between Hetero- and Hoplonemertea, which supports one of two recent alternative hypotheses of nemertean phylogeny.
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| 22. |
- Chen, Hai-Xia, et al.
(författare)
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Mutation and selection cause codon usage and bias in mitochondrial genomes of ribbon worms (Nemertea)
- 2014
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of codon usage bias is known to exist in many genomes and it is mainly determined by mutation and selection. To understand the patterns of codon usage in nemertean mitochondrial genomes, we use bioinformatic approaches to analyze the protein-coding sequences of eight nemertean species. Neutrality analysis did not find a significant correlation between GC12 and GC3. ENc-plot showed a few genes on or close to the expected curve, but the majority of points with low-ENc values are below it. ENc-plot suggested that mutational bias plays a major role in shaping codon usage. The Parity Rule 2 plot (PR2) analysis showed that GC and AT were not used proportionally and we propose that codons containing A or U at third position are used preferentially in nemertean species, regardless of whether corresponding tRNAs are encoded in the mitochondrial DNA. Context-dependent analysis indicated that the nucleotide at the second codon position slightly affects synonymous codon choices. These results suggested that mutational and selection forces are probably acting to codon usage bias in nemertean mitochondrial genomes. 7copy; 2014 Chen et al.
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| 23. |
- Chen, Hai-Xia, et al.
(författare)
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Statistical parsimony networks and species assemblages in cephalothricid nemerteans (Nemertea).
- 2010
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Ingår i: PLoS ONE. - 1932-6203. ; 5:9
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: It has been suggested that statistical parsimony network analysis could be used to get an indication of species represented in a set of nucleotide data, and the approach has been used to discuss species boundaries in some taxa. METHODOLOGY/PRINCIPAL FINDINGS: Based on 635 base pairs of the mitochondrial protein-coding gene cytochrome c oxidase I (COI), we analyzed 152 nemertean specimens using statistical parsimony network analysis with the connection probability set to 95%. The analysis revealed 15 distinct networks together with seven singletons. Statistical parsimony yielded three networks supporting the species status of Cephalothrix rufifrons, C. major and C. spiralis as they currently have been delineated by morphological characters and geographical location. Many other networks contained haplotypes from nearby geographical locations. Cladistic structure by maximum likelihood analysis overall supported the network analysis, but indicated a false positive result where subnetworks should have been connected into one network/species. This probably is caused by undersampling of the intraspecific haplotype diversity. CONCLUSIONS/SIGNIFICANCE: Statistical parsimony network analysis provides a rapid and useful tool for detecting possible undescribed/cryptic species among cephalotrichid nemerteans based on COI gene. It should be combined with phylogenetic analysis to get indications of false positive results, i.e., subnetworks that would have been connected with more extensive haplotype sampling.
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| 24. |
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| 25. |
- Chen, Hai-Xia, et al.
(författare)
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The mitochondrial genomes of two nemerteans, Cephalothrix sp (Nemertea: Palaeonemertea) and Paranemertes cf. peregrina (Nemertea: Hoplonemertea)
- 2011
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Ingår i: Molecular Biology Reports. - 0301-4851. ; 38:7, s. 4509-4525
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial genome sequences were determined for two species of nemerteans, Cephalothrix sp. (15,800 bp sequenced, near-complete) and Paranemertes cf. peregrina (14,558 bp, complete). As seen in most metazoans, the genomes encode 13 protein, 2 ribosomal RNA and 22 transfer RNA genes. The nucleotide composition is strongly biased toward A and T, as is typical for metazoan mtDNAs. There is also a significant strand skew in the distribution of these nucleotides, with the coding strand being richer in T than A and in G than C. All genes are transcribed in the same direction except for trnP and trnT, which is consistent with that reported for Cephalothrix hongkongiensis and Lineus viridis. Gene arrangement of Cephalothrix sp. is identical to that of C. hongkongiensis, while in P. cf. peregrina it is similar to L. viridis, but differs significantly from the three Cephalothrix species in the position of four protein-coding genes and seven tRNAs. Some protein-coding genes have 3' end stem-loop structures, which may allow mRNA processing without flanking tRNAs. The major non-coding regions observed in the two genomes with potential to form stem-loop structures may be involved in the initiation of replication or transcription. The average Ka/Ks values, varying from 0.12 to 0.89, are markedly different among the 13 mitochondrial protein-coding genes, suggesting that there may exist different selective pressure among mitochondrial genes of nemerteans.
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