An integrative taxonomic framework for the study of the genus Ciona (Ascidiacea) and description of a new species, Ciona intermedia

Abstract

The genus Ciona is an interesting ‘taxonomic case’ because its evolutionary history and taxonomy have not yet been resolved completely. In this study, we present new findings, describing specimens of an unidentified Ciona species collected along the north-eastern coasts of Sardinia (Tyrrhenian Sea, Mediterranean Sea). Applying an integrative taxonomic approach, based on the joint examination of morphological and molecular traits, we identify these specimens as a new species, Ciona intermedia sp. nov. Morphological comparisons and peculiarities of the habitat first revealed that these Ciona specimens have intermediate characters compared with other Ciona species. Molecular characterization (based on three mitochondrial regions: two already used for discriminating Ciona cryptic species and a newly developed one) confirmed that our specimens could not be assigned to any previously molecularly-characterized species. Both molecular phylogenetic reconstructions and morphological data clearly indicate C. intermedia as sister clade of Ciona edwardsi. Our findings add further complexity to the taxonomy of Ciona, underlying the importance of an integrative taxonomic approach for the study of the evolutionary history of this enigmatic genus.

An elongated COI fragment to discriminate botryllid species and as an improved ascidian DNA barcode

“…a Published in 93 . b Sequences of about 1100 bp obtained with the primer pair dinF/consR1 94 , but the amplicon dinF/Nux1R was also obtained from the same specimens. c Published in 95 .…”

An elongated COI fragment to discriminate botryllid species and as an improved ascidian DNA barcode

“…The map was created with ArcView GIS 3.2 (https://www.esri.com/). 93 (b): sequences of about 1100 bp obtained with the primer pair dinF/consR1 94 , but the amplicon dinF/Nux1R was also obtained from the same specimens (c): published in 95 Table 4 Bayesian Posterior Probability (BPP) and ML bootstrap percentage for the nodes within clade A shown in Figure 2 and Figure 3. Red: BPP ≥ 0.90 or ML bootstrap ≥ 80%.…”

“…Amplification of the 860-COI in non-botryllid ascidian species. "no-seq": amplicon checked by gel electrophoresis but not sequenced; "seq=": sequenced amplicon, producing a sequence equal to that of an AC number already in the ENA nucleotide database : sequences of about 1100 bp obtained with the primer pair dinF/consR194 , but the amplicon dinF/Nux1R was also obtained from the same specimens (c): published in95 …”

Molecular taxonomy confirms that the northeastern Atlantic and Mediterranean Sea harbor a single lancelet, Branchiostoma lanceolatum (Pallas, 1774) (Cephalochordata: Leptocardii: Branchiostomatidae)

“…Indeed, several species possess an Atlantic-Mediterranean distribution [87][88][89][90]. However, phylogeographical barriers between the Atlantic Ocean and the Mediterranean Sea and the geographical complexity of the Mediterranean have given rise to endemism, and cryptic and vicariant species, even among conspicuous species and model systems [82,[91][92][93][94].…”