Discovery of the tropical marine green alga <i>Phyllodictyon robustum</i> (Cladophorales, Boodleaceae) in a temperate region of Korea

Abstract We report the first molecular record of Phyllodictyon robustum , a tropical turf-forming green alga previously known only from the Pacific coasts of Mexico and Panama, in Korean waters (Hongdo, 3–5 m depth). Morphological analysis revealed key diagnostic features, including an erect thallus (2–6 cm), polygonal calcium oxalate crystals with dentate margins, lenticular cells, and reproductive structures with multiple raised pores. Molecular phylogenetic analyses using LSU rDNA, ITS, and SSU rRNA sequences confirmed its taxonomic identity, grouping Korean specimens with populations from Mexico and Panama. Haplotype network analysis indicated closer genetic affinity to Panamanian samples. These findings highlight the importance of an integrated taxonomic approach for tracking macroalgal biogeography and monitoring climate-driven range expansions and long-distance dispersal whether natural or human-mediated.