Exhaustive reanalysis of barcode sequences from public repositories highlights ongoing misidentifications and impacts taxa diversity and distribution: a case study of the Sea Lettuce.

• Main Authors: Fort, Antoine, McHale, Marcus, Cascella, Kevin, Potin, Philippe, Perrineau, Marie-Mathilde, Kerrison, Philip, Costa, Elisabete da, Calado, Ricardo, Domingues, Maria, Azevedo, Isabel Costa, Sousa-Pinto, Isabel, Gachon, Claire, Werf, Adrie van der, Visser, Willem de, Beniers, Johanna, Jansen, Henrice, Guiry, Michael, Sulpice, Ronan
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2020
• Subjects: North East Atlantic
• Online Access: http://dx.doi.org/10.22541/au.160622296.66033732/v1

Sea Lettuce ( Ulva spp. Ulvophyceae, Ulvales, Ulvaceae) is an important ecological and economical entity, with a worldwide distribution and is a well-known source of near-shore blooms blighting many coastlines. Species of Ulva are frequently misidentified in public repositories, including herbaria and gene banks, making species identification based on traditional barcoding hazardous. We investigated the species distribution of 295 individual distromatic foliose strains from the North East Atlantic by traditional barcoding or next generation sequencing. We found seven distinct species, and compared our results with all worldwide Ulva spp sequences present in the NCBI database for the three barcodes rbc L, tuf A and the ITS1. Our results demonstrate a large degree of species misidentification in the NCBI database. We estimate that 21% of the entries pertaining to foliose species are misannotated. In the extreme case of U. lactuca , 65% of the entries are erroneously labelled specimens of another Ulva species, typically U. fenestrata . In addition, 30% of U. rigida entries are misannotated, U. rigida being relatively rare and often misannotated U. laetevirens . Furthermore, U. armoricana and U. scandinavica present as being synonymous to U. laetevirens . An analysis of the global distribution of registered samples from foliose species also indicates possible geographical isolation for some species, and the absence of U. lactuca from Northern Europe. Altogether, exhaustive taxonomic clarification by aggregation of a library of barcode sequences highlights misannotations, and delivers an improved representation of Ulva species diversity and distribution. This approach could be easily adapted to other taxa.