DNA Barcoding for Herbarium Specimens of the Red Alga Meristotheca pilulaora and Molecular Marker Development for Species Identification

The genus <i>Meristotheca</i> (Gigartinales, Solieriaceae) comprises edible red algae that are economically important food ingredients in Korea, Japan, and China. In Korea, two species, <i>Meristotheca coacta</i> and <i>Meristotheca papulosa</i>, have been identified, with the latter being predominantly reported. Recently, molecular phylogenetic analysis enabled the identification of <i>Meristotheca pilulaora</i> (Gigartinales; Solieriaceae) on Jeju Island (Korea). In this study, we used a DNA barcoding method to re-examine <i>M. papulosa</i> herbarium specimens deposited at the National Institute of Biological Resources (Incheon, Korea). Specimens were collected from Korean coastal regions between 2009 and 2019. Molecular analyses based on the <i>rbc</i>L and <i>cox</i>1 sequences of the "<i>M. papulosa</i>" herbarium specimens revealed that the specimens were of two other species, <i>M. pilulaora</i> and <i>Gracilaria textorii</i> (Gracilariales; Gracilariaceae). Our work represents a case study for establishing a misidentification at the inter-ordinal level among herbarium specimens without DNA sequence verification. Moreover, we developed a molecular marker for the effective species-level identification of <i>M. pilulaora</i> and <i>G. textorii</i> specimens. The DNA barcoding method provides useful information regarding <i>M. pilulaora</i> distribution and taxonomy.