Sequencing of historic and modern specimens reveals cryptic diversity in Nothogenia (Scinaiaceae, Rhodophyta)

Nothogenia fastigiata has been reported to exhibit great morphological variability and has been considered to be widely distributed in the Southern Hemisphere. To test its current circumscription, sequences from type material of N. fastigiata and other species currently synonymized with it were compared to those from recent collections of this and other species in the genus. Eight distinct species previously subsumed under the name N. fastigiata were identified. Multiple specimens from southern Chile and a single specimen from Campbell Island (subantarctic New Zealand) were conspecific with type material of N. fastigiata from the Falkland Islands. For other species, molecular analyses of recent collections using the nuclear ITS1-5.8S-ITS2 region of the ribosomal cistron, the chloroplast rbcL and psbA genes and the mitochondrial COI gene indicated a strong geographic pattern to species relationships. Other specimens identified as N. fastigiata from Chile represented up to five species, including N. chilensis and N. fragilis, based on sequences of type material; these Chilean species occurred on a monophyletic branch. We also recognized N. lingula comb. nov. from Tasmania, which is closely related to N. fastigiata, based on sequences of type material. Specimens from mainland New Zealand identified as N. fastigiata fell into a distinct clade with New Zealand N. pulvinata and represented a previously undescribed species, described here as N. neilliae sp. nov. Another New Zealand species, N. pseudosaccata, was distantly related to N. variolosa from Auckland Island and other subantarctic islands south of New Zealand. The New Zealand species were more closely related to South African N. erinacea and N. ovalis than to species of Nothogenia from Chile, including N. fastigiata, although bootstrap support for this interpretation was weak. These genetic data demonstrate that matching DNA sequences from archival Nothogenia material to modern specimens can be used to identify and define new and old cryptic species.