Molecular and morphological characters distinguishing two Porphyra species (Rhodophyta: Bangiophycidae)

Definition of species limits within the rhodophyte genus Porphyra is hampered by the lack of reliable morphological markers; confusion in the taxonomy has serious implications for ecological studies. We report the results of a combined morphological and molecular analysis of plants variously referred to as P. purpurea, P. purpureo-violacea, P. umbilicalis F. laciniata and P, laciniata. All plants examined fell into one of two distinct groups: P, purpurea-monoecious with reproductive fronds divided into two distinct, but often unequal, male and female parts; P. laciniata-dioecious with fronds folding in half longitudinally when hanging vertically. All plants within a group were found to share a common nucleotide sequence for the chloroplast-bome rbcl.-S spacer; a single nucleotide transition separates the two groups.