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

Abstract

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 rbcL, tufA 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.

Harvest Time Can Affect the Optimal Yield and Quality of Sea Lettuce (Ulva fenestrata) in a Sustainable Sea-Based Cultivation

“…A Northern Hemisphere Ulva species that gained increasing attention due to its in-door (Olsson et al, 2020a;Toth et al, 2020) and large-scale outdoor cultivability (Steinhagen et al, 2021) is Ulva fenestrata Postels and Ruprecht. This foliose, marine species is widely distributed in Europe (Hughey et al, 2019;Steinhagen et al, 2019;Fort et al, 2020), shows promising biochemical profiles (Olsson et al, 2020a;Toth et al, 2020;Steinhagen et al, 2021) for diverse economic applications such as the food industry (Harrysson et al, 2018;Toth et al, 2020;Trigo et al, 2021) and its polysaccharides have been successfully used for innovative future materials (Wahlström et al, 2020a,b).…”