Ulva umbilicalis L. and Porphyra umbilicalis Kütz. ( Rhodophyta , Bangiaceae ): a molecular and morphological redescription of the species, with a typification update

Problems with the name and concept of the entity known as “ Porphyra umbilicalis ” that have led to confusion over its identity for more than 250 years are addressed. The name was first used by Kützing (1843), who provided a diagnosis based entirely on material collected from Scotland by Scheele, but he later subsumed it under another species. Jacob Agardh (1883) transferred Ulva umbilicalis L. (1753) to Porphyra . We show that this nomenclatural problem can be resolved by typifying the names Ulva umbilicalis L. and Porphyra umbilicalis Kütz. Although we have located a Scheele specimen of Porphyra , there is no evidence that Kützing based his description of P . umbilicalis on this material. We have therefore selected a specimen of P . umbilicalis from Scotland as neotype of P . umbilicalis Kütz. which fits both his diagnosis and the current concept of P . umbilicalis and for which we have molecular data. We also provide a revised diagnosis and designate the specimen chosen as the neotype of P . umbilicalis Kütz. as the epitype of Ulva umbilicalis L.