Key Kamchatkan collections provide new taxonomic and distributional insights for reportedly pan-North Pacific species of Rhodymeniophycidae (Rhodophyta)

Northwestern Pacific specimens of Callophyllis radula, Callophyllis rhynchocarpa, Pterosiphonia bipinnata and Sparlingia pertusa, all with type localities in Far East Russia, were genetically compared to reportedly conspecific populations in the Northeast Pacific. Analyses resolved genetically distinct species with a biogeographical split between the Northwest and Northeast Pacific for C. radula, C. rhynchocarpa and P. bipinnata. Callophyllis variforma sp. nov. was established to accommodate Northeast Pacific plants previously attributed to C. radula; whereas, synonymy of the Northeast Pacific C. flabellulata with the Northwest C. rhynochocarpa was refuted. To accommodate the species in the Northeast Pacific previously attributed to P. bipinnata, the epithet P. robusta was resurrected. Comparison of Northwest to Northeast Pacific S. pertusa revealed COI-5P variation consistent with incipient speciation between these two regions; however, subsequent analysis of the ITS2 provided evidence for recognition of a single species with a pan-North Pacific distribution. Our results indicated greater floristic division between the Northwest and Northeast Pacific than is currently recognised.