Nuclear rDNA sequences of Wittrockiella amphibia (Collins) comb. nov. (Cladophorales, Chlorophyta) and morphological characterization of the mat-like growth form

Abstract

Abstract Cladophora amphibia was found in Yaquina Bay (Oregon, USA) for the first time since the type collection from California in 1903. Vegetative plants were buried in the top centimeter of intertidal mud, partially covered by mats of Rhizoclonium and Chaetomorpha. Cladophora amphibia plants had densely pigmented upright branches penetrating the mud surface and overlying algal mats. Morphological and habitat characteristics of C. amphibia strongly overlap with those of Wittrockiella paradoxa, and molecular sequences of ribosomal genes, including the variable internally transcribed spacer 2 (ITS2) region, indicate very high genetic similarity between these two taxa. The seven point mutations in the ITS2 DNA sequences are regarded as low intraspecific variation. Since C. amphibia had been described earlier, W. paradoxa becomes a taxonomic synonym of C. amphibia, and the new binomial Wittrockiella amphibia (Collins) comb. nov. is required. As previously reported for W. paradoxa, the studied Pacific plants were “cladophoroid” in form (upright, branched thalli with cylindrical cells), in contrast to the stunted and poorly branched “rhizoidal” plants mainly found in Europe. The heterotrichous mode of growth is further characterized.