Rediscovery of the rare Cladochroa chnoosporiformis Skottsberg from the Falkland Islands and its merger with Utriculidium durvillei Skottsberg

The Subantarctic brown alga Cladochroa chnoosporiformis had been collected only on one occasion by Carl Skottsberg in 1907 from Port Philomel, West Falkland, Falkland Islands, resulting in its formal taxonomic description. Due to the lack of reports since then, doubts remained about its existence and identity. Within the framework of this study, Cladochroa was rediscovered 106 years after its original description at its type locality, confirming its existence and the morphological features described by Skottsberg. The re-collection enabled molecular studies on field material and isolated cultures. Sequences of nrDNA, rbcL, and 5’-COI suggest that C. chnoosporiformis is conspecific with Utriculidium durvillei, which has nomenclatural priority. However, the morphologies of C. chnoosporiformis and U. durvillei are significantly different. Utriculidium may be the gametophyte generation of Cladochroa, or hitherto unknown factors cause alternate, highly different morphologies due to evolution of alternating generations.