Phylogeny of Tunicata inferred from molecular and morphological characters

Department of Biological Sciences, University of Arkansas, 019 West Avenue Annex, Fayetteville 72701, USA.
Molecular Phylogenetics and Evolution (Impact Factor: 3.92). 01/2003; 25(3):408-28. DOI: 10.1016/S1055-7903(02)00305-6
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The phylogeny of the Tunicata was reconstructed using molecular and morphological characters. Mitochondrial cytochrome oxidase I (cox1) and 18S rDNA sequences were obtained for 14 and 4 tunicate species, respectively. 18S rDNA sequences were aligned with gene sequences obtained from GenBank of 57 tunicates, a cephalochordate, and a selachian craniate. Cox1 sequences were aligned with the sequence of two ascidians and a cephalochordate obtained from GenBank. Traditional, morphological, life history, and biochemical characters of larval and adult stages were compiled from the literature and analyzed cladistically. Separate and simultaneous parsimony analyses of molecular and morphological data were carried out. Aplousobranch ascidians from three different families were included in a molecular phylogenetic analysis for the first time. Analysis of the morphological, life history, and biochemical characters results in a highly unresolved tree. Aplousobranchiata form a strongly supported monophylum in the analysis of the 18S rDNA data, the morphological data, and the combined data set. Cionidae is not included in the Aplousobranchiata but nests within the Phlebobranchiata. Appendicularia (=Larvacea) nest within the 'Ascidiacea' as the sister taxon of Aplousobranchiata in the parsimony analysis of the 18S rDNA data and the combined analysis. A potential morphological synapomorphy of Aplousobranchiata plus Appendicularia is the horizontal orientation of the larval tail. In the 18S rDNA and the combined analysis, Thaliacea is included in the 'Ascidiacea' as the sister group to Phlebobranchiata. Pyrosomatida is found to be the sister taxon to the Salpidae in analyses of 18S rDNA and combined data, whereas the analysis of the morphological data recovers a sister group relationship between Doliolidae and Salpidae. Results of cox1 analyses are incongruent with both the 18S rDNA and the morphological phylogenies. Cox1 sequences may evolve too rapidly to resolve relationships of higher tunicate taxa. However, the cox1 data may be useful at lower taxonomic levels.

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Available from: Thomas Stach, Oct 13, 2015
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    • "possesses many characteristics that make it attractive as animal model: (i) O. dioica occupies a key phylogenetic position within the chordate phylum as a basally divergent member of the urochordate subphylum (Stach and Turbeville, 2002; Swalla et al., 2000; Wada, 1998), which is the sister group of vertebrates (Delsuc et al., 2006; Delsuc et al., 2008). O. dioica, therefore, is a useful model to infer the ancestral condition from which vertebrate and other urochordate species evolved. "
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    ABSTRACT: The genome sequencing and the development of RNAi knockdown technologies in the urochordate Oikopleura dioica are making this organism an attractive emergent model in the field of EvoDevo. To succeed as a new animal model, however, an organism needs to be easily and affordably cultured in the laboratory. Nowadays, there are only two facilities in the world capable to indefinitely maintain Oikopleura dioica, one in the SARS institute (Bergen, Norway) and the other in the Osaka University (Japan). Here, we describe the setup of a new facility in the University of Barcelona (Spain), in which we have modified previously published husbandry protocols to optimize the weekly production of thousands of embryos and hundreds of mature animals using the minimum amount of space, human resources and technical equipment. This optimization includes novel protocols of cryopreservation and solid cultures for long-term maintenance of microalgal stocks - Chaetoceros calcitrans, Isochrysis sp., Rhinomonas reticulata and Synechococcus sp.- needed for Oikopleura dioica feeding. Our culture system maintains laboratory partially inbred lines healthy with similar characteristics to wild animals, and it is easily expandable to satisfy on demand the needs of any laboratory that may wish to use Oikopleura dioica as a model organism. © 2014 Wiley Periodicals, Inc.
    genesis 07/2014; 53(1). DOI:10.1002/dvg.22800 · 2.02 Impact Factor
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    • "At high taxonomic level the most remarkable questions are the branching pattern between the three tunicate classes (Thaliacea, Larvacea and Ascidiacea), the correlated issue of the Ascidiacea paraphyly (Wada 1998; Stach and Turbeville 2002; Zeng and Swalla 2005; Yokobori et al. 2006; Zeng, Jacobs, Swalla 2006; Swalla and Smith 2008; Tsagkogeorga et al. 2009; Govindarajan, Bucklin, Madin 2011), and the Phlebobranchia paraphyly (Swalla et al. 2000; Turon and Lopez-Legentil 2004; Yokobori, Oshima, Wada 2005; Zeng and Swalla 2005; Tsagkogeorga et al. 2009; Stach, Braband, Podsiadlowski 2010; Rubinstein et al. 2013). At low taxonomic level, exemplifying cases are the relationships among the Aplousobranchia families (Turon and Lopez-Legentil 2004; Tsagkogeorga et al. 2009), the paraphyly of Pyuridae with respect to Styelidae (Perez-Portela et al. 2009; Rubinstein et al. 2013), the possible inclusion of Cionidae within Aplousobranchia rather than Phlebobranchia (Kott 1990; Stach and Turbeville 2002; Turon and Lopez-Legentil 2004), up to the existence of cryptic species in several ascidians (Tarjuelo et al. 2001; Tarjuelo et al. 2004; Perez-Portela and Turon 2008). Cryptic speciation has been reported even in the model organisms Ciona intestinalis (Suzuki, Nishikawa, Bird 2005; Caputi et al. 2007; Iannelli et al. 2007b; Nydam and Harrison 2007; Nydam and Harrison 2010; Zhan, Macisaac, Cristescu 2010) and Botryllus schlosseri (Bock, MacIsaac, Cristescu 2012). "
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    Genome Biology and Evolution 02/2014; 6(4). DOI:10.1093/gbe/evu041 · 4.23 Impact Factor
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    • "To verify whether secondary sensory cells are a plesiomorphic or apomorphic feature of tunicates, we analyzed the mouth of three species of thaliaceans, pelagic tunicates in which hair cells have not yet been characterized (Fig. 1A–D). In agreement with classical taxonomic views, all recent phylogenetic reports based on the analysis of nuclear and mitochondrial genes have consistently identified the monophyletic nature of thaliaceans, although their position with respect to the other tunicates is still under discussion (Burighel et al., 1992; Wada et al., 1998; Swalla et al., 2000; Stach and Turbeville, 2002; Yokobori et al., 2005; Tsagkogeorga et al., 2009). Within the thaliaceans, a commonly accepted view places pyrosomes in a basal position, with doliolids and salps being sister groups, following a trend toward branchial sac simplification and muscle-band development (Govindarajan et al., 2011). "
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    The Journal of Comparative Neurology 08/2013; 521(12). DOI:10.1002/cne.23313 · 3.23 Impact Factor
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