Untangling the peacock's tail: Species diversity, taxonomy and origins of the economically valuable brown alga Padina (Dicyotales, Phaeophyceae) in Korea

Abstract

The brown algal genus Padina demonstrated compelling potential for applications in food and biotechnology, arising from its valuable reservoir of minerals, macro- and micro-nutrients, and bioactive compounds. The genus was first reported in Korea in 1892, and to date, a total of six species has been recognized in Korea using a traditional taxonomic morphology-based approach. Nevertheless, there have been disagreements regarding the presence of some of these species, and the paucity of genetic studies undertaken on this group in Korea to date has hindered efforts to close this gap in knowledge. To address this, we conducted an extensive sampling of specimens of Padina across the southern half of the Korean peninsula and neighboring islands. Molecular analyses revealed the presence of four Padina species: P. arborescens, P. crassa, P. imbricata (recorded in Korea for the first time), and P. japonica. Our study, in conjunction with prior research, confirmed the distinctiveness of P. crassa and P. gymnospora, leading us to propose the reinstatement of P. crassa as a separate species. The four identified species in Korea have a dual origin: while P. arborescens, P. crassa, and P. imbricata have historical origins in the East Pacific, P. japonica originated from the Central Indo-Pacific. The genetic divergence and time of divergence observed between these species and the American lineages/species suggests that they are not the result of introduction but rather historical natural dispersal, likely facilitated by oceanic currents. These findings allowed concluding that the four species found in Korea are indigenous to this region. The genus Padina exhibits vast potential for various applications briefly reviewed here, and we strongly advocate for its commercial utilization in Korea. Particularly, P. arborescens, which showed promising pharmaceutical properties and can dominate the seabed in parts of the Korean coast, warrants special attention in this regard.