Morphology and taxonomy of Southern Australian Genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta)

Abstract

The southern Australian species of the tribe Crouanieae Schmitz (Ceramiaceae. Rhodophyta) have been studied with particular reference to their taxonomy relationships. and phylogeny; in all cases the type specimens have been examined. Three tribes. Crouanieae. Antithamnieae. and Heterothamnieae. can be recognized. including 16 genera. of which Euptilocladia. Macrothamnion. Tetuathamnion. Amoenothamnion. and Trithamnion are newly described and 48 species (26 newly described) . Recognition of the subfamilies Crouanioideae and Ceramioideae. as defined by Hommersand (1963). is not supported by these studies .Features of greatest taxonomic significance are those indicative also of phylogenetic trends and hence the classification is based upon concepts of phylogeny. Evolutionary advance in both morphological and reproductive features involves specialization, particularly towards adaptations in form with relation to function. The Crouanieae, Antithamnieae, and Heterotharnnieae are probably primitive groups of the Ceramiaceae. The Antithamnieae and Heterothamnieae are closely related and probably arose from the same evolutionary line, while Crouanieae has evolved independently. Thalli in the Heterothamnieae are smaller and less specialized than those of the most advanced species of Antithamnieae, and it is likely that the Heterothamnieae arose as a branch from the Antithamnieae line of development through specialization in reproductive features rather than thallus form. Both morphological and reproductive features are discussed and it is shown that Hommersand's definition of Antithamnieae must be modified, particularly in reference to procarp development. The probable phylogenetic lines revealed form useful bases for comparisons and provide a logical approach to the taxonomy of the group. Taxonomic features used in classification and reasons for the terminology adopted are also discussed. Analyses of records indicating the geographic distribution of species within southern Australia provide few useful conclusions.