Distributions of three Asiatic Porphyra species, Porphyra yezoensis Ueda, Porphyra katadae A. Miura, and Porphyra suborbiculata Kjellm., are reported from New England, USA. Species identifications were confirmed by rbcL and nuclear ribosomal DNA internal transcribed spacer-1 (ITS1) sequence comparisons with herbarium specimens, cultures, and GenBank accessions. Two distinct genotypes of P. yezoensis were detected: forma narawaensis A. Miura and f. yezoensis. Forma narawaensis occurs south of Cape Cod, Massachusetts, and has ITS1 sequences identical to cultivars widely grown in Japan. Forma yezoensis occurs in western Long Island Sound and from Cape Cod northward to midcoastal Maine; its ITS1 sequence is identical to a wild specimen from Hokkaido, Japan. P. katadae has been collected from five locations near Cape Cod; its ITS1 sequence is identical to a cultured specimen from Qingdao, China. P. suborbiculata has been collected at several locations south of Cape Cod; its presence in North Carolina and Delaware during the mid-1960s was confirmed from herbarium specimens. Morphological and ecological characteristics for New England populations of the three Asiatic species were compared to original descriptions. New England P. yezoensis f. yezoensis is similar to Ueda's original description of Japanese specimens, but there are morphological differences for P. yezoensis f. narawaensis. In New England, f. narawaensis typically does not attain the length reported in Japan (max. 19 cm versus 100 cm). New England P. katadae is similar to Miura's original description, except for slight differences in thallus thickness and reproductive patterns. By contrast, New England, Japanese, and other populations of P. suborbiculata exhibit pronounced differences in blade coloration, shape and dimensions, reproductive patterns, seasonal occurrence, and general ecology.
