An introduced population of C horda asiatica ( C hordaceae, L aminariales) in P uget S ound, P acific coast of N orth A merica

Summary Northeastern P acific O cean and northwestern A tlantic O cean populations of C horda species, which have not been examined in previous phylogenetic studies, were investigated. All specimens that were collected in H ood C anal, P uget S ound, WA , USA , P acific coast of N orth A merica, showed identical ITS ‐5.8S rDNA sequences, and they were included in the clade of Japanese C horda asiatica . With morphological data added to the molecular data, they were identified as C . asiatica and were concluded to be non‐indigenous populations, most likely introduced with oyster spat together with S argassum muticum . Specimens collected in N ew Y ork, NY , USA , Atlantic coast of N orth A merica, were genetically closest to C . filum from N ewfoundland and were identified as C . filum. The genetic divergence of the North Atlantic populations of C . filum was relatively small compared to that of J apanese C . asiatica considering their broader distributional ranges on both sides of the A tlantic.