Ottia meiospora (Ottiaceae, Rhodophyta), a new genus and family endophytic within the thallus of Nothocladus (Batrachospermales, Rhodophyta).

A new genus, Ottia, and family, Ottiaceae, are proposed within the Acrochaetiales to accommodate the uniseriate red algal endophyte of batrachspermalean taxa previously named Balbiania meiospora. Prior to this study, Balbiania investiens was transferred to its own family and order (Balbianiales) based on comparative DNA sequence data and a distinctive reproductive morphology. However, the second species described in this genus, B. meiospora, continued to be treated as a species of Audouinella (A. meiospora) pending further investigation. Phylogenetic analyses of sequence data confirmed only a distant relationship between the two endophytes, and a closer alliance of B. meiospora to Acrochaetiales. The data also showed that Ottia meiospora was the deepest diverging lineage in the Acrochaetiales, sister to all of the currently recognized genera and families. In this study, we review the classification of what we now call O. meiospora - reported from Australia, New Zealand and Brazil - based on sequence and morphological data. Morphological observations provided little clarity around the reproductive morphology or the life cycle of this endophyte of Nothocladus s. lat. found commonly in mainland Australia but, to date, less so in New Zealand.