The different morphs of Undaria pinnatifida (Phaeophyceae, Laminariales) in Peter the Great Bay (Sea of Japan) are phenotypic variants: direct evidence

Previous study elicited three morphologically distinct forms of Undaria pinnatifida in Peter the Great Bay (Sea of Japan), which were represented by one or more populations. It was supposed that their specific morphology is plastic response to the local environment. In the present study, we used molecular data in order to examine directly the degree of genetic similarity between these morphs. We performed amplified fragment length polymorphism and microsatellite analyses. In addition, offspring of these forms were cultivated in the same environments. It was shown that genetic polymorphism of U. pinnatifida in Peter the Great Bay is low. The genetic distance among five populations representing three forms of U. pinnatifida did not exceed 0.2. The offspring of three forms grown in the same environmental conditions became, in general, morphologically similar. Combination of genetic analysis and cultivation in the same environmental conditions of three morphologically different forms of U. pinnatifida from Peter the Great Bay suggested that their specific morphology is not genetically fixed and is the result of ontogenetic adaptation to the local environment.