Monograph of the green macroalgal genus Rhipilia (Udoteaceae, Halimedales), with a description of R. crassa sp. nov. from Australia and the Philippines

Abstract

Examination of type and authentic material of the eleven currently recognized species of the green macroalgal genus Rhipilia Kützing has shown that the most useful features for distinguishing species are the disposition and diameters of the blade siphons; tenacular number, position and shape; and the type and location of siphon constrictions. Several attributes that have previously been given major taxonomic weight, such as plant colour, habit (including frond thickness, degree of prominence of concentric markings on the blades, and degree of stipe elongation) and habitat associations do not appear to be sufficiently consistent to be useful in themselves for many species delineations. Two species (Rhipilia diaphana and R. tenaculosa) are placed in synonymy (with R. orientalis and R.tomentosa, respectively). All but the two most recently described species (R. penicilloides and R. nigrescens) are reinvestigated and illustrated, with particular emphasis placed on three (R. sinuosa, R. orientalis and R. crassa A. Millar & Kraft, sp.nov.) that occur along the southern Great Barrier Reef of eastern Australia and in southeastern Luzon, Philippines. Distinguishing features of R. crassa are the lack of clear differentiation between stalk and blade, the relatively large filament diameters (up to 130 μm),the coarse, regularly rectilinear meshworks of the blades, and the large numbers of prongs, some of them forked, on the tenacula.