An introduced population of Chorda asiatica (Chordaceae, Laminariales) in Puget Sound, Pacific coast of North America

摘要

Northeastern Pacific Ocean and northwestern Atlantic Ocean populations of Chorda species, which have not been examined in previous phylogenetic studies, were investigated. All specimens that were collected in Hood Canal, Puget Sound, WA, USA, Pacific coast of North America, showed identical ITS-5.8S rDNA sequences, and they were included in the clade of Japanese Chorda 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 Sargassum muticum. Specimens collected in New York, NY, USA, Atlantic coast of North America, were genetically closest to C.filum from Newfoundland and were identified as C.filum. The genetic divergence of the North Atlantic populations of C.filum was relatively small compared to that of Japanese C.asiatica considering their broader distributional ranges on both sides of the Atlantic.