A systematic study of the red algal family Halymeniaceae

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Our molecular phylogenetic analyses using the rbcL gene indicate : the morphology of auxiliary cell ampullae and carpogonial branch apparatuses has taxonomic significance at the genus level in the Halymeniaceae, although the texture and habit of blades and the position of reproductive structures hitherto used for distinguishing genera are homoplacious. Our analyses also indicate that such homoplacious characters have taxonomic significance at the species level along with quantitative features such as the width and height of blades and the size of reproductive cells. (1)Carpopeltis affinis (Harvey) Okamura and C.prolifera (Hariot) Kawaguchi et Masuda and Sinkoraena consisting of two species should be transferred to Polyopes on the basis of the similarity of auxiliary cell ampullae and carpogonial branch apparatuses. The rbcL gene sequences support such transfers (The genus Sinkoraena was reduced to synonymy with Polyopes). (2)A new species Polyopes tosaensis Kawaguchi et Masuda and a reinstated species Grateloupia subpectinata Holmes are cryptic species that have been included in other species. (3)An alga collected from Yonaguni Island, Okinawa Prefecture, is characterized by the behavior of cells in the auxiliary cell ampullar filaments immediately after diploidization, most cells of the primary and secondary filaments simultaneously dividing to form grape-like clusters of small globular cells. This alga was resolved by our rbcL, analyses as one of five monophyletic clades within the Halymeniaceae, which is positioned as sister to the Grateloupia clade. A new genus Yonagunia was erected on the basis of this alga (Y.tenuifolia Kawaguchi et Masuda, sp.nov.). The Southeast Asian alga Prionitis formosana (Okamura) Kawaguchi et Nguyen that has the above-mentioned feature and included in the same clade was transferred to Yonagunia.