Back to solitude: Solving the phylogenetic position of the Diazonidae using molecular and developmental characters

A phylogenomic framework and timescale for comparative studies of tunicates

“…Hence, our choice to root our trees according to Philippe et al [39], which in any case does not affect the phylogenetic relationships of chordates. The results from this first phylogenomic study including all tunicate lineages were in line with recent studies [20,[25][26][27][28] demonstrating that ascidians (Class Ascidiacea) form a paraphyletic group. Our results showed that phlebobranchs and aplousobranchs are undoubtedly closer to thaliaceans than to stolidobranchs (Fig.…”

“…Even though the position of Thaliacea was not always statistically supported, it consistently appeared as the sister-group of phlebobranchs + aplousobranchs in previous studies [20,[24][25][26]28], except for a recent genome-scale study in which the positioning of Salpa thompsoni most likely suffered artefactual LBA attraction towards the fast-evolving appendicularians [66]. The robust phylogenetic position of thaliaceans found here indicates that they likely evolved from a sessile ancestor and their study can provide valuable information on the morphological transformations associated with the transition to the pelagic lifestyle [29].…”

“…Despite renewed interest in tunicate evolution, phylogenetic relationships among the major tunicate lineages remain uncertain. Previous molecular phylogenetic studies relying on 18S rRNA [23][24][25][26] and mitogenomes [20,27,28] have proposed first delineations of major tunicate clades, revoking the traditional 19 th century classification into the three classes Appendicularia (larvaceans), Thaliacea (salps, doliolids, and pyrosomes), and Ascidiacea (phlebobranchs, aplousobranchs, and stolidobranchs). Indeed, these studies found unanimous support for the paraphyly of Ascidiacea (ascidians) owing to the inclusion of thaliaceans in a clade also containing two main ascidian lineages (phlebobranchs and aplousobranchs) to the exclusion of stolidobranch ascidians (molgulids, pyurids, and styelids).…”

Ascidiacea (Chordata: Tunicata) of Greece: an updated checklist

“…Aplousobranchia and Stolidobranchia are the most speciose orders with 32 and 25 species, respectively. Aplousobranchia reach 36 species, if the families Diazonidae and Cionidae are included therein instead of Phlebobranchia, as suggested by various ascidian taxonomists based on morphological, developmental, and molecular data (Kott 1990, Turon and López-Legentil 2004, Shenkar and Swalla 2011, Shenkar et al 2016a) but not currently adopted by AWD. The families Didemnidae (14 species), Polyclinidae (12 species), Pyuridae (12 species), Ascidiidae (10), and Styelidae (9 species) comprised the highest number of species, covering altogether 76% of the Greek ascidian species richness.…”

“…Furthermore, the original classification of Lahille (1886), which classified the ascidian species into the orders Aplousobranchia, Phlebobranchia, and Stolidobranchia according to the structure of the branchial sac, is supported by molecular phylogeny and is currently accepted by most taxonomists (Shenkar and Swalla 2011). However, there are still different views on the placement of several families into orders, and the phylogenetic relationships within the ascidians remain fuzzy (Turon and López-Legentil 2004, Moreno et al 2008, Pérez-Portela et al 2009, Tsagkogeorga et al 2009, Shenkar et al 2016a). …”