Taxonomic revisions based on genetic analysis of type specimens of Ulva conglobata, U. laetevirens, U. pertusa and U. spathulata (Ulvales, Chlorophyta)

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.