Morpho-anatomical and molecular characterization indicates overlooked taxonomic diversity in the Antarctic genus Hymenocladiopsis (Rhodymeniales, Rhodophyta)

Abstract

ABSTRACT Wide morphological variation has been described in the Antarctic macroalga Hymenocladiopsis prolifera, suggesting that there could be overlooked taxonomic diversity in the genus Hymenocladiopsis, which is currently considered to be monotypic. To clarify the taxonomy of the genus, morpho-anatomical and reproductive characters of specimens of Hymenocladiopsis were evaluated and genetic analyses were performed using the molecular markers COI-5P and rbcL. Our results indicate the presence of two groups within the Hymenocladiopsis samples, clearly differentiated both genetically and anatomically, which correspond to two distinct but closely related species. We described the main morpho-anatomical differences between these two species, and we recognized a name for each of them: H. prolifera (Reinsch) M.J. Wynne and H. crustigena R.L. Moe. Our results also indicate the occurrence of two morphotypes within H. crustigena specimens that are genetically identical but morphologically different, this variability being allegedly explained by a wide range of intraspecific phenotypic plasticity.