Taxonomy of the New Zealand‐endemic Genuspleurostichidium(rhodomelaceae, Rhodophyta)

A morphological, anatomical, and molecular study of the tribe Pleurostichidieae (Rhodomelaceae, Ceramiales) is presented. New collections of its only member, Pleurostichidium falkenbergii Heydrich, have enabled a thorough re-assessment of this species from a classical-morphological standpoint and have allowed the first photographs to be made of critical features of this little-known obligate epiphyte of the brown alga Xiphophora chondrophylla (Turner) Montagne ex Harvey. The relationship of the tribe to other members of the Rhodomelaceae is considered based on analysis of 18S rDNA sequences from P. falkenbergii, 14 other rhodomelaceous species, and six outgroup taxa. Pleurostichidium falkenbergii is shown to be most closely related to the tribe Polysiphonieae and only distantly related to the Amansieae, with which it was previously associated.