Reinstatement of Grateloupia catenata (Rhodophyta, Halymeniaceae) on the basis of morphology and <i>rbc</i>L sequences

Abstract

Morphological observations and molecular analysis of a red alga, which has been known as Grateloupia filicina var. lomentaria, G. filicina var. porracea f. lomentaria, or Sinotubimorpha porracea (Cryptonemiales, Halymeniaceae) in the western Pacific, were made for field-collected and cultured plants. The auxiliary-cell ampullae lack tertiary filaments and are of the Grateloupia-type. Morphologically, this alga can be distinguished from G. filicina by (1) the hollow axis; (2) the numerous short proliferations with Lomentaria-like constrictions that densely cover the surface of erect axes in mature plants; and (3) a tendency for reproductive structures to be restricted to the proliferations. The presence of 4.2–4.6% (62–67 bp) nucleotide substitutions in the ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) between G. filicina and the alga in question also strongly supports the differentiation of these two entities at the species level. The form of the proliferations distinguishes the alga in question from the West Indies G. porracea. Re-examination of type material of Grateloupia catenata Yendo, which has been placed into synonymy under Grateloupia filicina var. porracea f. lomentaria, revealed that our freshly collected specimens matched it, and therefore the Yendo name is reinstated. The topological position of Grateloupia catenata in rbcL trees does not support its separation from other Grateloupia species at the generic rank.