Recognition of Rubrointrusa membranacea gen. et comb. nov., Rhodonematella subimmersa gen. et comb. nov. (with a reinterpretation of the life history) and the Meiodiscaceae fam. nov. within the Palmariales (Rhodophyta)

Abstract

Clayden S.L. and Saunders G.W. 2010. Recognition of Rubrointrusa membranacea gen. et comb. nov., Rhodonematella subimmersa gen. et comb. nov. (with a reinterpretation of the life history) and the Meiodiscaceae fam. nov. within the Palmariales (Rhodophyta). Phycologia 49: 283–300. DOI: 10.2216/09-43.1

Two members currently classified in the florideophyte Colaconematales, Colaconema membranaceum and C. subimmersum, display life history and morphological/anatomical characteristics suggestive of some Palmariales, prompting the current investigation. We observed a direct life history by regenerative tetrasporangia for C. membranaceum as previously reported and provide the first evidence of sexual reproduction in C. subimmersum from the Pacific northeast, corroborating reports from Japan. However, the life history pattern in C. subimmersum is reinterpreted as intermediate between that typical of the Palmariaceae and Rhodophysemataceae. We addressed the phylogenetic affinities of these two species by sequencing large-subunit ribosomal DNA and the ‘DNA barcode’ (5′ region of the cytochrome oxidase subunit I gene), which was also used to assess species diversity. In phylogenetic analyses both C. membranaceum and C. subimmersum were unequivocally supported as members of the Palmariales. Colaconema membranaceum displayed a weak affinity for species of Meiodiscus but is distinct in its endozoic basal system, and we propose Rubrointrusa gen. nov., typified by Rubrointrusa membranacea (Magnus) comb. nov. Colaconema subimmersum, consistently grouped with species of Rhodophysema but is divergent from these species in habit, life history, and molecular signature, so that we propose a new monotypic genus Rhodonematella, typified by Rhodonematella subimmersa (Setchell & N.L. Gardner) comb. nov. Rhodonematella, is provisionally placed in the Rhodophysemataceae. We concomitantly examined the phylogenetic affinities of Halosacciocolax kjellmanii and Meiodiscus spp., both tentatively included in the Rhodophysemataceae. Halosacciocolax kjellmanii is retained in the Rhodophysemataceae and transferred to Rhodophysema, Rhodophysema kjellmanii (S. Lund) comb. nov., based on our molecular results and new anatomical observations. Conversely, Meiodiscus species resolved independently of other palmarialean families, and we propose the Meiodiscaceae fam. nov. to accommodate them, as well as Rubrointrusa. Meiodiscus concrescens is restricted to populations from the northeast Pacific; whereas, so-called Atlantic M. concrescens is conspecific with M. spetsbergensis.

Key Words::

• Colaconema membranaceum
• Colaconema subimmersum
• Halosacciocolax
• Meiodiscaceae
• Meiodiscus
• Palmariales
• Rhodonematella
• Rhodophyta
• Rubrointrusa
• Systematics

ACKNOWLEDGMENTS

Bob Hooper kindly collected hydroids with endozoic C. membranaceum from Newfoundland, and Gerhard Pohle identified the host hydroids from New Brunswick and Nova Scotia. Mohammad Afzal, Natasha Chishti, Bethany Hermann, Ali Johnson, and Line Le Gall provided mitochondrial barcode sequences for some Palmariales, Tanya Moore the LSU for H. kjellmanii, and Todd Harper and Geoff Nicki the LSUs for P. mollis and P. decipiens, respectively. The Bamfield Marine Sciences Centre in British Columbia and the Bonne Bay Ocean Sciences Centre in Newfoundland are thanked as hosts during various collecting excursions. We thank Craig Schneider and Paul Silva for advice on our new generic names and Mark Garland for providing the Latin diagnoses. Kyatt Dixon and Dan McDevit generously read parts of the manuscript, and the thoughtful comments of two anonymous reviewers improved the manuscript. GWS received Natural Sciences and Engineering Research Council of Canada (NSERC) and Canada Research Chair program grants as well as infrastructure support from the Canada Foundation for Innovation and the New Brunswick Innovation Foundation. Barcoding of taxa in this study was supported through funding to the Canadian Barcode of Life Network from Genome Canada (through the Ontario Genomics Institute), NSERC, and other sponsors listed at http://www.BOLNET.ca.

Corrigendum

Correction to the paper by Clayden S.L. and Saunders G.W. 2010. Recognition of Rubrointrusa membranacea gen. et comb. nov., Rhodonematella subimmersa gen. et comb. nov. (with a reinterpretation of the life history) and the Meiodiscaceae fam. nov. within the Palmariales (Rhodophyta). Phycologia 49(3): 283–300.

In Table 1, page 286, Genbank # GU2241123 is correctly GU224123.