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

The genus Meristotheca (Gigartinales, Solieriaceae) comprises edible red algae that are economically important food ingredients in Korea, Japan, and China. In Korea, two species, Meristotheca coacta and Meristotheca papulosa, have been identified, with the latter being predominantly reported. Recently, molecular phylogenetic analysis enabled the identification of Meristotheca pilulaora (Gigartinales; Solieriaceae) on Jeju Island (Korea). In this study, we used a DNA barcoding method to re-examine M. papulosa 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 rbcL and cox1 sequences of the “M. papulosa” herbarium specimens revealed that the specimens were of two other species, M. pilulaora and Gracilaria textorii (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 M. pilulaora and G. textorii specimens. The DNA barcoding method provides useful information regarding M. pilulaora distribution and taxonomy.