Phylogenetic reconstructions of the Hedwigiaceae reveal cryptic speciation and hybridisation in Hedwigia

A molecular based study of relationships in the Hedwigiaceae, with a special focus on the genus Hedwigia in Europe was carried out. A combined approach using sequence data from all three genomes, information obtained from the secondary structures of the nad5 group I intron, and morphological data was performed in order to clarify species concepts in the Hedwigia ciliata -complex. In agreement with earlier studies the separation of Rhacocarpus in its own family Rhacocarpaceae can be rejected. The genus is related to Braunia and therefore clearly belongs to the Hedwigiaceae. Based on molecular data Pseudobraunia californica is shown to be related to Hedwigia . Since several of the morphological characters are of questionable systematic value and the remaining characters are few, a separation in its own genus is inappropriate. We transfer Pseudobraunia californica back to Hedwigia californica . We show that the Hedwigia ciliata -complex in Europe consists of at least 4 species, Hedwigia ciliata , Hedwigia stellata , Hedwigia striata (which is here transferred back to species rank) and a cryptic species of which we do not have enough information yet to identify it as one of the existing taxa or as a new species. All Australian specimens included in our analyses, which were believed to be Hedwigia ciliata s. str., belong to this taxon rendering the occurrence of Hedwigia ciliata s. str. in Australia questionable. Hedwigia ciliata var. leucophaea cannot be maintained with its current morphological circumscription. The distinguishing characters can obviously be developed independently in some taxa of the Hedwigia ciliata complex. Furthermore we found evidence for potential hybridisation in some of the specimens determined as Hedwigia ciliata var. leucophaea , as nuclear and organellar DNA is originating from different taxa. Based on the presented results, Hedwigia striata (Wilson) Bosw. is recognized as a distinct species with more or less distinctly plicate leaves and straight rather than flexuose perichaetial leaf cilia.