Cryptic species diversity and the misapplication of names have restricted an understanding of species boundaries in the tribe Corallineae of the calcified red algal order Corallinales. Recent DNA sequencing of type material provided a framework facilitating further examination of genera within the tribe. A phylogenetic study of the genera Corallina and Ellisolandia, based on cytochrome c oxidase subunit 1 and ribulose-bisphosphate carboxylase gene sequences, was undertaken using Natural History Museum herbarium collections and contemporary samples to explore species diversity, geographic distributions and the extent to which names have been misapplied. Twenty Corallina clades likely corresponding to species were resolved, of which C. officinalis and C. caespitosa were confirmed, four were clades newly identified during the present study and 14 had been reported by other workers in previous studies. These data indicated considerable genetic diversity within the genus that was not readily apparent on the basis of morphology. The generitype C. officinalis was shown to have a predominantly North Atlantic Ocean, cool-temperate distribution, whereas the global distribution of C. caespitosa is confirmed for the first time, with samples from Asia, Australasia, Europe, Africa and America. Widespread misidentification of Corallina species was documented, as was the need for sequencing of type specimens to correctly apply names and for comparison with historical collections. The phylogeny reported here serves both as a baseline for future phylogenetic positioning of Corallina species and highlights the degree to which species concepts within this genus remain unresolved.

No abstract

North‐Atlantic records of Schizymenia dubyi extend along the eastern shores of the North Atlantic from Morocco to southern Britain and Ireland, and the species is also recorded from Iceland. A study was undertaken to confirm the identity of the specimens from Iceland that were geographically separate from the main distribution of S. dubyi and in contrast to other species of the genus did not have gland cells. We analyzed rbcL and COI molecular sequence data from Icelandic specimens and compared the results with those for Schizymenia specimens available in GenBank. For both markers, Schizymenia was shown to be a monophyletic genus. The Icelandic specimens were clearly genetically distinct from S. dubyi and formed a well‐supported clade with Schizymenia species from the Northern Pacific. Based on these results, we have described a new species, Schizymenia jonssonii, which can be distinguished by molecular phylogeny, its lack of gland cells and by being strictly intertidal. Crustose tetrasporophytes with identical COI and rbcL sequences were found at the same locations as foliose plants. Schizymenia apoda is reported for the first time in the UK, its identity confirmed by rbcL sequence data. In light of these findings, it is likely that by further molecular analysis of the genus Schizymenia in the north‐eastern Atlantic and the Mediterranean, a higher diversity of Schizymenia spp. will be discovered in this region.