Southern Australian species of Polysiphonia Greville (Rhodophyta)

Abstract

Twenty-six species of Polysiphonia are recognized from the coast of southern Australia. Their relationships are discussed, their distribution outlined and ecological notes are given.

Characters found to be satisfactory for species delimitation include the number of pericentral cells. presence or absence and degree of cortication, whether or not rhizoids are cut off from the parent pericentral cells, the origin of lateral branches near apices (whether from the basal cell of trichoblasts or independent of them), the habit of the thallus, and dimensions and proportions of the thallus and segments of the branches. The presence and frequency of trichoblasts (or scar cells) may be characteristic but can vary with activity of growth of the thallus in some species. Cystocarps offer few characters, though the degree of enlargement of the ostiolar cells may be useful in some species. In male plants, satisfactory characters are whether the spermatangial branch replaces the whole trichoblast or only one basal furcation, and the presence or not of sterile apical cells. The form of the tetrasporangial branchlets and arrangement of tetrasporangia are often useful.

Of the 26 species, 17 belong to subgenus Oligosiphonia and nine to subgenus Polysiphonia.

Four species (P. scopulorum, P. subtilissima, P. sertularioides and P. brodiaei) are species of widespread distribution, the last-named possibly spread by shipping. One species (P. pungens) is known from the Pacific Coast of Canada and now from the State of Victoria. Some 17 species appear to be restricted to southern Australia, including I1 species newly described (P. haplodasyae, P. shepherdii, P. brevisegmenta, P. amphibolis, P.perriniae. P.propagulqera, P. australiensis, P. abscissoides, P. teges, P. constricta and P. adamsiae). Two species (P. decipiens, P. isogona) occur in southern Australia, New Zealand, and possibly subantarctic regions, while two others (P. abscissoides, P. adamsiae) occur both in New Zealand and in southern Tasmania. One species (P. haplodasyae) is a very small species apparently confined to its host Haplodasya.

It appears that P. mollis has been recorded incorrectly from various other countries, and clearly much more critical study of the species of Polysiphonia is needed, especially of early species described from the Mediterranean and West Indies.