Pneophyllum fragile in southern Australia: implications for generic concepts in the Mastophoroideae (Corallinaceae, Rhodophyta)

Abstract

Studies of the type collection and southern Australian populations of Pneophyllum fragile Kützing, the type species of Pneophyllum(Corallinaceae, Rhodophyta), have shown that considerable variation occurs both in the vegetative thallus and in conceptacle anatomy. Vegetative plants vary from 2–50+ cells in thickness, and thallus margins may be two or more cells in thickness. Tetrasporangial conceptacle roof anatomy also varies in terms of roof thickness, pore canal length, and the occurrence of a columella, but all pore canals are lined by cells that are oriented more or less parallel to the thallus surface, and protruding into the canal, and roofs are formed by filaments surrounding the sporangial initials and interspersed amongst them. These new morphological and anatomical data have shown that Pneophyllum and Spongites can be regarded as distinct genera on the basis of the mode of the tetrasporangial conceptacle formation, but not on differences in thallus thickness, as formerly. In addition, Pneophyllum lejolisii (Rosanoft) Chamberlain is considered to be a heterotypic synonym of Pneophyllum fragile.