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Species of Ulva Linnaeus are nearly impossible to identify using morpho-anatomy due to their simple thallus structure and phenotypic plasticity. The current solution to this problem is to sequence DNA from field-collected specimens and match these sequences to those available in public DNA databases. However, because type specimens of many species have not been sequenced, the accuracy of these identifications is highly doubtful. Ulva rigida C.Agardh is reported to be one of the most widespread and ecologically important Ulva species, but these records are based on either morpho-anatomy or, more recently, on DNA sequences. High-throughput sequencing (HTS) was performed on the lectotype specimen of U. rigida from Cádiz, Spain to determine the correct application of the name. The analysis yielded its complete plastid genome. rbcL, tufA and ITS sequences from the lectotype specimen differed at the species level from all U. rigida sequences deposited in public databases. Instead, the lectotype sequences of U. rigida were identical or very similar to sequences identified as U. rotundata Bliding (referred to by some as U. pseudorotundata Cormaci, G.Furnari & Alongi) from Ireland and Portugal, but not to the holotype of U. rotundata from Italy, which was identical to U. lactuca L. HTS of the lectotype of U. lacinulata (Kützing) Wittrock from Lesina, Croatia, a species morphologically similar to U. rigida with macroscopic marginal teeth, also yielded a complete plastid genome, with sequences identical or highly similar to GenBank U. armoricana Dion, Reviers & Coat, U. 'laetevirens', U. 'rigida' and U. scandinavica Bliding. Since U. lacinulata is the oldest validly published name, it is the correct one to apply to the globally distributed species that was previously but incorrectly known as U. rigida. Based on this genetic evidence, U. rigida is restricted to European waters and confirmed by DNA sequences from Ireland, Portugal and Spain. This analysis shows that many barcode species identifications and taxonomic conclusions in the genus Ulva are incorrect. Ulva rigida was misapplied and is restricted to Atlantic Europe. Ulva lacinulata is the dentate species of Ulva distributed worldwide. Ulva rotundata is a heterotypic synonym of U. lactuca. [ABSTRACT FROM AUTHOR]

SUMMARY: Genetic analysis of type material of various Ulva species has shown that many names have been misapplied. DNA sequences of two of the specimens on the lectotype sheet of U. australis from South Australia showed that U. australis is conspecific with specimens called U. pertusa from Japan. However, type material of U. pertusa has not been sequenced, nor have other type specimens with type localities in Japan and Australia, including U. conglobata f. conglobata and U. conglobata f. densa from the former, and U. laetevirens and U. spathulata from the latter. To determine if these names have been correctly applied, targeted DNA sequencing of the rbcL gene was performed on (i) the lectotype specimen of U. laetevirens, (ii) the lectotype and two syntype specimens of U. pertusa, (iii) the lectotype and two syntype specimens of U. congoblata f. conglobata and (iv) two specimens on the holotype sheet of U. conglobata f. densa. In addition, high‐throughput sequencing (HTS) analysis was carried out on an isotype specimen of U. spathulata. Phylogenetic analysis of the resulting rbcL gene sequences supports the taxonomic conclusions that U. laetevirens, U. pertusa and U. spathulata are synonyms of U. australis, and U. conglobata f. conglobata and U. conglobata f. densa represent a single separate and distinct species, U. conglobata. These genetic data contribute to the taxonomy of Ulva and further demonstrate that analyzing DNA from type material is the only currently known reliable method to correctly apply names in this genus. [ABSTRACT FROM AUTHOR]

Green macroalgae, mostly represented by the Ulvophyceae, the main multicellular branch of the Chlorophyceae, constitute important primary producers of marine and brackish coastal ecosystems. Ulva or sea lettuce species are some of the most abundant representatives, being ubiquitous in coastal benthic communities around the world. Nonetheless the genus also remains largely understudied. This review highlights Ulva as an exciting novel model organism for studies of algal growth, development and morphogenesis as well as mutualistic interactions. The key reasons that Ulva is potentially such a good model system are: (i) patterns of Ulva development can drive ecologically important events, such as the increasing number of green tides observed worldwide as a result of eutrophication of coastal waters, (ii) Ulva growth is symbiotic, with proper development requiring close association with bacterial epiphytes, (iii) Ulva is extremely developmentally plastic, which can shed light on the transition from simple to complex multicellularity and (iv) Ulva will provide additional information about the evolution of the green lineage. [ABSTRACT FROM AUTHOR]

Polyopes lancifolius (Harvey) S. Kawaguchi & H.W. Wang has been recorded for the first time in Europe, during the summer of 2008. A small population was discovered in the Gulf of Morbihan (northeast Atlantic, France). This is the first observation of P. lancifolius outside its native range. Vegetative and reproductive morphological features are compared with previous descriptions. rbcL sequences show no divergence from Japanese populations. Imports of Pacific oysters Crassostrea gigas (Thunberg 1793) are likely to be responsible for its accidental introduction into the Gulf of Morbihan, either directly from northwest Pacific regions or indirectly (secondary dispersal) by transfers from another European oyster farming site. The history of previous algal introductions from Japan suggests that if it becomes successfully established at Morbihan, the species is likely to spread to other European coastal areas. [ABSTRACT FROM AUTHOR]