Gracilaria species (Gracilariaceae, Rhodophyta) from southeastern Australia, including a new species, Gracilaria perplexa sp. nov.: Morphology, molecular relationships and agar content

SUMMARY Select species of the agarophyte Gracilaria were studied from southeastern Australia. The morphology and anatomy of species is described and molecular relations are inferred based on plastid and mitochon-drial DNA sequence data. Agar yields and qualities are determined for each species. Gracilaria chilensis, found in Tasmania and Victoria, is morphologically and molecularly similar to G. chilensis from New Zealand and Chile and has low agar yields of 11–16%. Gracilaria cliftonii from Victoria, has high crude agar yield (52%) and is molecularly uniform. Gracilaria perplexa sp. nov., known only from Botany Bay, New South Wales, has an agar yield of 39%. The agar of G. perplexa is unusual in requiring the addition of 0.1 mol L−1 NaCl for alcohol precipitation and is cold-water (25°C) soluble because of the very high sulfate ester content. Molecular phylogeny shows that G. perplexa is closely related to Gracilaria preissiana from western Australia, but differs from the latter in its reduced branching and narrower more terete axes.