Revision of the Mastophoroideae (Corallinales, Rhodophyta) and Polyphyly in Nongeniculate Species Widely Distributed on Pacific Coral Reefs1

Abstract

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.

Convergence of joint mechanics in independently evolving, articulated coralline algae

“…This evolutionary trajectory is supported both by the fossil record (Aguirre et al, 2010;Kundal, 2011) and by molecular phylogenetics (Bailey and Chapman, 1998;Bittner et al, 2011;Kato et al, 2011). Moreover, these data suggest that articulated thalli are polyphyletic, evolving from crustose corallines multiple times and leading to three distinct phylogenetic groups of articulated coralline algae: Corallinoideae, Amphiroideae and Metagoniolithoideae ( Fig.…”

“…Mechanical Kato et al, 2011). 'Amphiroideae' refers to Amphiroideae sensu Johansen (1981), and is separated from the rest of Lithophylloideae here for clarity.…”

Nongeniculate coralline red algae (Rhodophyta: Corallinales) in coral reefs from Northeastern Brazil and a description of Neogoniolithon atlanticum sp. nov.

“…However, Kato et al (2011) concluded that differences in trichocyte arrangement could be used to separate the two supported lineages at a generic level: Hydrolithon for horizontally arranged fields of trichocytes with interspersed vegetative filaments, and Porolithon (resurrected) for horizontally arranged, tightly packed fields of trichocytes without interspersed vegetative filaments. Similarities in the formation of cells around the pores of tetrasporangial conceptacles led the latter authors to propose that Porolithon is a heterotypic synonym of Hydrolithon.…”

“…Bailey et al (2004) used molecular biology techniques, but not morphological features, and combined P. pachydermum with Hydrolithon pachydermum (Foslie 1904: 4) Bailey, Gabel & Freshwater (2004: 8), as did Broom et al (2008), who recognised genetic similarities between H. pachydermum and H. onkodes. Kato et al (2011) used molecular analyses of SSU rDNA and psbA sequences to divide Japanese coralline algae into independent polyphyletic lineages for the Mastophoroideae genera examined (Hydrolithon, Neogoniolithon, Pneophyllum Kützing (1843: 385), Porolithon and Spongites). They also proposed the establishment of three new subfamilies, Hydrolithoideae (including Hydrolithon), Porolithoideae (including the resurrected genus Porolithon) and Neogoniolithoideae (including Neogoniolithon).…”

“…Therefore, evaluating the anatomic features of the tetrasporangial conceptacle is necessary to delimit genera and species in a modern context (Woelkerling 1988). Kato et al (2011) and Bittner et al (2011) have updated the taxonomy of this group, proposing several new subfamilies and the resurrection of the genus Porolithon Foslie (1909: 57). However, regional surveys are necessary to develop a complete picture of how the coralline species might be delimited in each region.…”