title: Back to solitude: Solving the phylogenetic position of the Diazonidae using molecular and developmental characters.
abstract: The order Aplousobranchia (Chordata, Ascidiacea) contains approximately 1500 species distributed worldwide. Their phylogeny, however, remains unclear, with unresolved family relationships. While most Aplousobranchia are colonial, debates exist concerning the phylogenetic position of families such as the Diazonidae and Cionidae, which exhibit a solitary lifestyle and share morphological characteristics with both Aplousobranchia and Phlebobranchia orders. To clarify the phylogenetic position of the Diazonidae and Cionidae, we determined the complete mitochondrial sequence of the solitary diazonid Rhopalaea idoneta. The phylogenetic reconstruction based on the 13 mitochondrial protein coding genes strongly supports a positioning of Diazonidae well-nested within the Aplousobranchia rather than a positioning as a sister clade of the Aplousobranchia. In addition, we examined the regenerative ability of R. idoneta. Similar to colonial Aplousobranchia, R. idoneta was found to be able to completely regenerate its thorax. Ciona, also known to possess high regenerative abilities, is the Aplousobranchia sister clade rather than a member of the Phlebobranchia. Our results thus indicate that the colonial lifestyle was acquired in the Aplousobranchia, starting from a Ciona-like solitary ancestor and secondarily lost in Diazonidae representatives such as Rhopalaea. The solitary lifestyle of Rhopalaea is thus a derived characteristic rather than an ancestral trait.
authors.affiliation: Department of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 6997801, Israel; Steinhardt Museum of Natural History and Israel National Center for Biodiversity Studies, Tel-Aviv University, Tel-Aviv 6997801, Israel. Electronic address: shenkarn@post.tau.ac.il.
authors.forename: Noa
authors.initials: N
authors.lastname: Shenkar
authors.affiliation: Department of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 6997801, Israel; Steinhardt Museum of Natural History and Israel National Center for Biodiversity Studies, Tel-Aviv University, Tel-Aviv 6997801, Israel; Eilat Campus, Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; The Inter-University Institute for Marine Sciences of Eilat, Eilat, Israel.
authors.forename: Gil
authors.initials: G
authors.lastname: Koplovitz
authors.affiliation: Department of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors.forename: Liran
authors.initials: L
authors.lastname: Dray
authors.affiliation: Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", Bari, Italy.
authors.forename: Carmela
authors.initials: C
authors.lastname: Gissi
authors.affiliation: Department of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 6997801, Israel; Steinhardt Museum of Natural History and Israel National Center for Biodiversity Studies, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors.forename: Dorothée
authors.initials: D
authors.lastname: Huchon
mesh_terms: D000818:Animals; D054629:Genome, Mitochondrial; D008928:Mitochondria / Q000235:genetics; D010802:Phylogeny; D012038:Regeneration / Q000235:genetics; D014561:Urochordata / Q000145:classification* / Q000196:embryology / Q000235:genetics*
keywords: Aplousobranchia; Mitochondrial genome; Mitogenomics; Phylogeny; Rhopalaea; Thorax-regeneration