Taxonomic investigation of Ralfsia-like (Ralfsiales, Phaeophyceae) taxa in the North Atlantic Ocean based on molecular and morphological data, with descriptions of Pseudoralfsiaceae fam. nov., Pseudoralfsia azorica gen. et sp. nov. and Nuchella vesicularis gen. et sp. nov.

ABSTRACT

In this study we investigated Ralfsia-like crusts (i.e. excluding Ralfsia sensu stricto, Stragularia spp. and/or Scytosiphonaceae crustose phases) with an emphasis on the North Atlantic Ocean using molecular data (COI-5P, ITS and rbcL-3P) combined with morpho-anatomical comparisons of type material and contemporary specimens. Of the four species of Ralfsia previously reported in Europe, only R. fungiformis is presently recognized as belonging to Ralfsia sensu stricto, Ralfsiaceae, with the remaining species, R. lucida, R. ovata and R. verrucosa, of uncertain taxonomic status. Our study revealed 11 independent genetic lineages of Ralfsia-like taxa, which were not assignable to any of the recognized families of the Ralfsiales. To accommodate this diversity, we propose Pseudoralfsiaceae Parente, Fletcher & G.W.Saunders fam. nov., including two new genera Pseudoralfsia Parente, Fletcher & G.W.Saunders gen. nov. and Nuchella Parente, Fletcher & G.W.Saunders gen. nov. The first genus includes Pseudoralfsia verrucosa (Areschoug) Parente, Fletcher & G.W.Saunders comb. nov. as the generitype (the only species of the three remaining European species of uncertain taxonomic status assigned to Ralfsia that was reassessed here), P. azorica Parente, Fletcher & G.W.Saunders sp. nov. and seven undescribed genetic groups, which require additional vouchers for description. The second genus has as generitype Nuchella vesicularis Parente, Fletcher & G.W.Saunders sp. nov., and also includes N. sp._1MP, which was represented by a single sterile specimen from Swanage, UK and consequently not characterized. Three characteristics differentiate Nuchella from Pseudoralfsia – the former typically with numerous vesicles, non-synchronous development of the plurangia and hair pits arising from both middle and lower cells of the erect filaments. Species of Pseudoralfsiaceae can be distinguished from Ralfsia sensu stricto (Ralfsiaceae) mainly by DNA sequences and by consistently having frequent hair pits, and typically unsymmetrical thalli.

KEYWORDS:

• Brown crusts
• COI-5P
• DNA barcode
• Nuchella vesicularis
• phylogenetic
• Pseudoralfsia azorica
• Pseudoralfsia verrucosa
• Pseudoralfsiaceae
• Ralfsiales
• taxonomy

Acknowledgments

Many thanks to previous and current members of the Saunders Laboratory for technical assistance and for valued advice and helpful discussions. We thank all the collectors listed in Supplementary table S1 for their critical involvement in this project. Thanks also to Ana Ferreira, Elisabete Dias, Ricardo Camarinho, Maximilian Müller and Sophia Griese for laboratory help, Ana C. Costa, Mónica Moura and Armindo Rodrigues for making available laboratory equipment and Ana C. Costa also for helpful comments. Thanks are also due to Alvin K. Chan, K. Dixon, D. McDevit and T. Moore for generating some of the sequence data. We gratefully acknowledge the trustees of the US National Herbarium and Swedish Museum of Natural History for organizing loans of type material and providing helpful taxonomic information. We also thank Michael Wynne for assistance in interpreting historical taxonomic literature and Craig Schneider and António Frias Martins for assistance with Latin.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary information

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at http://dx.doi.org/10.1080/09670262.2020.1753245

Supplementary table S1. Specimens included in the present study with collection information and GenBank accession numbers. Reproductive specimens are indicated with ^a and ^b (for plurangia and unangia respectively), and accession numbers of the sequences used in the concatenated alignment are marked in bold type.

Supplementary table S2. Sequences retrieved from GenBank with collection information, publication and accession numbers. ^{a, b, c, d} are used to distinguish samples of the same species.

Author contributions

M.I. Parente: original concept, drafting and editing manuscript, sample descriptions; molecular data analyses and interpretation; R.L. Fletcher: original concept, sample descriptions, editing manuscript; F.O. Costa: original concept, molecular data analyses, editing manuscript; G.W. Saunders: original concept, drafting, editing manuscript, molecular data analyses, sample descriptions.

Additional information

Funding

This research was funded by FEDER funds through the Programa Operacional Factores de Competitividade – COMPETE and by national funds through FCT – Foundation for Science and Technology in the scope of the MACROBIOMOL project (ref. PTDC/MAR/114613/2009) and under the UID/BIA/50027/2013 and POCI-01-0145-FEDER-006821 programmes. Work completed in the Saunders Laboratory was supported by the Canadian Barcode of Life Network from Genome Canada in association with the Ontario Genomics Institute, the Natural Sciences and Engineering Research Council of Canada, as well as other sponsors listed at www.boldsystems.org, with infrastructure support from the Canada Foundation for Innovation and New Brunswick Innovation Foundation.