<i>Reinboldiella koreana</i> sp. nov. (Ceramiales, Rhodophyta) is the correct name for the specimens previously known as <i>Reinboldiella schmitziana</i> in Korea

Epiphytic algae are important components of marine ecosystems. Despite the importance of epiphytic algae in marine ecosystems, our knowledge of these taxa is still limited. The marine red algal genus <i>Reinboldiella</i>, which is distributed mainly in the northwestern Pacific region, is characterized by tiny thalli that are epiphytic on various other red algae. Six species of the genus have been reported in Japan, Taiwan, and Korea. In this study, 50 Korean Reinboldiella specimens, previously known as <i>Reinboldiella schmitziana</i>, were collected from 11 localities and reexamined to verify their taxonomic status. We describe a new species, <i>Reinboldiella koreana</i> sp. nov., based on <i>rbc</i>L phylogeny and morphological observations. A total of four grateloupiacean species (<i>Pachymeniopsis lanceolata</i>, <i>P. elliptica</i>, <i>Grateloupia turuturu</i>, and <i>G. asiatica</i>) were identified as host species of <i>R. koreana</i> sp. nov. Due to the restricted host range of <i>R. koreana</i> sp. nov., a phylogenetic tree was reconstructed using the <i>cox</i>1 marker to confirm the co-phylogenetic relationships between the epiphytic algae and their grateloupiacean hosts. Two of the four cox1 haplotypes of <i>R. koreana</i> were found in different host species, regardless of which haplotype they were. It indicates that there are no co-phylogenetic relationships between <i>R. koreana</i> and host species.