Validation and phylogenetic placement of the Placentophoraceae fam. nov. (Gigartinales, Rhodophyta)

ABSTRACT

Despite recent evidence that has shown a close phylogenetic relationship between Callophycus (familia incertae sedis) and the monotypic genus Placentophora (previously regarded as a member of the family Solieriaceae), the phylogenetic relationships of these genera within the order Gigartinales have not been unequivocally established. Although the family name Placentophoraceae was used for Callophycus and Placentophora in 2013, this taxon has yet to be properly validated in accordance with the rules of the International Code of Nomenclature for Algae, Fungi and Plants, thus rendering the Placentophoraceae a nomen nudum. Our present study has generated new rbcL and COI-5P sequences for the generitype species of Placentophora, P. colensoi, and combined them with corresponding data from several species of Callophycus, as well as from other representatives of the Gigartinales, to confirm that Callophycus and P. colensoi form a family-level clade within that order. The exact relationships of this clade to other gigartinalean families, however, is undetermined. In order to validate the Placentophoraceae, a detailed description of the family is supplied, based largely on the most recent molecular, morpho-taxonomic and phytochemical information. The Placentophoraceae are shown to consist of Callophycus (with 10 western Indo-Pacific species, eight of which are limited to Australia) and the monotypic New Zealand genus Placentophora.

KEYWORDS:

• Callophycus
• Gigartinales
• Molecular-assisted alpha taxonomy
• Placentophora
• Placentophoraceae
• Rhodophyta
• Solieriaceae

ACKNOWLEDGEMENTS

John M. Huisman, Joe Zuccarello and an anonymous reviewer contributed comments that improved the quality of this article. We are grateful to John McNeil for his help with the rules nomenclature and to Michael Wynne for assistance with literature and for nomenclatural advice.

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Funding

Support for this study was provided through a grant to R.V. Dumilag from the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (DOST-PCAARRD) Science Education Institute through an Accelerated Science and Technology Human Resources Development Programme (DOST-SEI ASTHRDP) and the Far Eastern University, University Research Center (FEU-URC). The Strategic Science Investment Funds (SSIF) grant to the National Institute of Water and Atmospheric Research (NIWA) Marine Platform to W.A. Nelson and material support of the Tasmanian Herbarium to G.T. Kraft are also acknowledged.