Morphological and molecular variability of Porphyra purpurea (Roth) C.!Agardh (Rhodophyta, Bangiales) from the Northwest Atlantic

The morphology, genetic variability and reproductive patterns of Northwest Atlantic populations of Porphyra purpurea were evaluated in relation to geography, ecology, and season. Identifications of specimens were confirmed by RFLP assay and rbcL sequences, while molecular comparisons within the species utilized rbcL and ITS I sequences. Identical rbcL sequences were documented for coastal and estuarine populations and from diverse geographic locations ranging from the Canadian Maritime Provinces to Long Island Sound, as well as three locations in Europe. Phenotypic plasticity in P. purpurea was found to be far greater than previously understood, yet specimens from the extremes of the morphological ranges had 100% identical rbcL sequences. Sequences for the ITS I region were 99.6% identical between orbicular and fusiform morphologies of P. purpurea collected at Blomidon Beach, Nova Scotia, Canada. Porphyra purpurea occurs throughout the year and is an aseasonal annual. By contrast to most previous reports of the plant being monoecious, we found it to be trioecious with unisexual male plants being more common than either monoecious or separate female plants. Endosporangia were also abundant on unisexual male plants.