Confirmation on Taxonomic Status of Spatoglossum pacificum Yendo (Dictyotaceae, Phaeophyceae) Based on Morphology and Plastid Protein Coding rbcL, rbcS, psaA, and psbA Gene Sequences

Phonological, morphological and molecular characteristics of Spatoglossum pacificum Yendo are examined. S. pacificum has an annual life cycle composed of saprophytes with apparent absence of male and female gametophytes in Korea. The seasonal growth of this species explains that the annual growth is closely related to the monthly variation of water temperature. S. pacificum has protruding reproductive structures above the outmost cortical layer. Although this observation is restricted to several species, reproductive structures on the thallus can make S. pacificurn distinguishable from S. crassum and S. lacturn. The morphogenesis of a midrib at the base of S. pacificum in this study is the same as those of Dictyopteris but different from those of S. crassum and S. lacturn, suggesting that S. pacificum is closely related to Dictyopteris. In the comparison of plastid gene sequences among species of Spatoglossum and Dictyopteris, S. pacificum is more similar to D. divaricata and D. undulate than those of S. crassum in rbcL, rbcS, psbA and psaA. This result is congruent with the anatomical characteristic of a midrib at the base of the thallus and the protrusion of reproductive organs on the thallus. The phylogenetic relationship based on these plastid genes also shows that S. pacifism is included in Dictyotpteris Glade and separated from S. crassum. We propose the new combination of Dictyopteris pacifica (Yendo) I.K. Hwang, H.S. Kim et W.J. Lee, comb. nov. based on the differences of anatomical characteristics of the midrib, the existence of reproductive organs on thallus and the molecular analyses.