• Aki Kato,

    1. Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko, Motobu, Okinawa 905-0227, Japan
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    • Author for correspondence: e-mail

    • Present address: Takehara Fisheries Research Station, Center for Education and Research of Field Science, Hiroshima University, Minato-machi, Takehara, Hiroshima 725-0024, Japan.

  • Masasuke Baba,

    1. Marine Ecology Research Institute, Kashiwazaki, Niigata 945-0017, Japan
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  • Shoichiro Suda

    1. Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-0213, Japan
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  • Received 22 June 2010. Accepted 2 November 2010.


The subfamily Mastophoroideae (Corallinaceae, Rhodophyta) is characterized by species possessing nongeniculate, uniporate tetrasporangial conceptacles without apical plugs, the presence of cell fusions, and the absence of secondary pit connections. However, molecular phylogenetic studies not including the type genus Mastophora indicated that the Mastophoroideae was polyphyletic. Our molecular phylogenetic analysis of the subfamily including the type genus using DNA sequences of SSU rDNA and plastid-encoded gene of PSII reaction center protein D1 (psbA) revealed that Mastophora formed a robust clade only with Metamastophora. The other mastophoroid genera were divided into six lineages within the family Corallinaceae. Five supported lineages—(i) Pneophyllum; (ii) Hydrolithon gardineri (Foslie) Verheij et Prud’homme, Hydrolithon onkodes (Heydr.) Penrose et Woelk., and Hydrolithon pachydermum (Foslie) J. C. Bailey, J. E. Gabel et Freshwater; (iii) Hydrolithon reinboldii (Weber Bosse et Foslie) Foslie; (iv) Spongites; and (v) Neogoniolithon—were clearly distinguished by the combination of characters including the presence or absence of palisade cells and trichocytes in large, tightly packed horizontal fields and features of tetrasporangial and spermatangial conceptacles. Therefore, we amend the Mastophoroideae to be limited to Mastophora and Metamastophora with a thin thallus with basal filaments comprised of palisade cells, tetrasporangial conceptacles formed by filaments peripheral to fertile areas, and spermatangia derived only from the floor of male conceptacles. This emendation supports Setchell’s (1943) original definition of the Mastophoroideae as having thin thalli. We also propose the establishment of three new subfamilies, Hydrolithoideae subfam. nov. including Hydrolithon, Porolithoideae subfam. nov. including the resurrected genus Porolithon, and Neogoniolithoideae subfam. nov. including Neogoniolithon. Taxonomic revisions of Pneophyllum and Spongites were not made because we did not examine their type species.