engleski

Barcoding of thaliacea in the Adriatic

The coverage of Thaliacea species has been relatively good regarding 18S. The 18S gene is highly conserved, therefore of limited use in delimiting closely related species and unsuitable for population-level studies. This is demonstrated by the fact that Thalia democratica and Thalia longicauda, which are morphologically quite distinct, possess identical 18S sequences. COI has been traditionally the most common barcode gene, because of its ability to differentiate species and populations and relative ease of amplification across taxa, but thaliacean COI sequences are scarce, so much so that COI barcodes of only five Thaliacea species are available. The general absence of available thaliacean sequences is likely due to a combination of factors: lack of taxonomists as well as inability of the commonest COI primers (namely, LCO1490 and HCO2198) to reliably amplify COI gene fragments across thaliacean taxa. Within the framework of SpaTeGen project, in an effort to produce COI sequences of Adriatic thaliaceans, we combined multiple primer pairs and produced doliolid and salpid COI sequences of more than 800 bps, encompassing HCO2198 binding site. Our preliminary results show that pyrosomatid and doliolid sequences are 6 aminoacids longer than salpid sequences, in the first 300 aminoacid stretch. Preliminary phylogenetic analysis based on COI sequences place salpids as a sister clade to pyrosomatids and doliolids. This is in contrast to published phylogeny based on 18S, which place pyrosomatids as the most ancestral group from which doliolids and salpids branch off in succession.

thaliacea ; barcoding ; Adriatic Sea

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