Cryptic diversity in non-geniculate coralline algae: a new genus Roseolithon (Hapalidiales, Rhodophyta) and seven new species from the Western Atlantic

ABSTRACT

Molecular studies have revealed cryptic diversity and polyphyly in the genus Lithothamnion. In this study we aimed to investigate the diversity and phylogeny of specimens that are morphologically described as Lithothamnion based on extensive collections along the Brazilian coast and an integrative taxonomic approach. Our results led to the proposal of Roseolithon gen. nov. belonging to the subfamily Melobesioideae. This new genus is described from the tropical north-western Atlantic and warm temperate south-western Atlantic specimens, based on phylogenetic analyses of psbA, rbcL-3P, COI-5P and SSU rDNA molecular markers, species delimitation methods, genetic divergence and morpho-anatomical observations. The integrative approach led us to find a set of morphological features that characterize Roseolithon: (i) thallus organization monomerous with plumose hypothallus (non-coaxial); (ii) flared epithallial cells; (iii) subepithallial cells varying in size and may be shorter, approximately equal to or longer than those subtending them; (iv) cells of adjacent filaments linked by fusions; (v) tetra/bisporangial conceptacle chambers multiporate; and (vi) the presence of pore canals bordered by rosette cells in depressions giving the surface a pitted appearance. Depending on the species, this pitted appearance occurs due to the sunken or disintegrated rosette cell roofs. The grade of the degeneration of the rosette cell roofs characterizes the species of this genus. The new genus Roseolithon is composed of at least 18 species, of which we describe seven new species: Roseolithon tupii, R. tamoioi, R. tremembei, R. potiguarae, R. karaiborum, R. purii and R. goytacae.

Highlights

• Phylogenetic analyses revealed Lithothamnion to be a polyFphyletic genus.

• Integrative taxonomy enabled the description of a new genus Roseolithon.

• Morpho-anatomy does not reflect molecular phylogeny of non-geniculate coralline algae.

KEYWORDS:

• Algae
• calcifying algae
• COI-5P
• Melobesioideae
• psbA
• rbcL-3P
• south-western Atlantic
• species delimitation methods

Acknowledgements

We thank Rosário Petti and Willian Oliveira for technical support, Joana C. Oliveira for help with Amerindian people names, and Nilber Gonçalves da Silva for the corrections on Latinizing the epithets. Collections were made with authorization provided by ICMBio (Instituto Chico Mendes de Conservação da Biodiversidade) and NUC/IDEMA (Instituto de Desenvolvimento Sustentável e Meio Ambiente do Rio Grande do Norte).

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 https://doi.org/10.1080/09670262.2021.1950839

Supplementary table S1. List of samples extracted and successfully amplified in this study. - indicates no data available.

Supplementary table S2. Sample information for species included in the molecular analyses.

Supplementary table S3. Levels of intraspecific genetic variation (diagonal in dark grey) and interspecific variation (in percentage, under the diagonal) for psbA sequences, based on uncorrected p-distance between studied taxa. Intraspecific variation values are presented in bold. (n=), number of sequences/species analysed; -, absent values.

Supplementary table S4. Levels of intraspecific genetic variation (diagonal in dark grey) and interspecific variation (in percentage, under the diagonal) for rbcL-3P sequences, based on uncorrected p-distance between studied taxa. Intraspecific variation values are presented in bold. (n=), number of sequences/species analysed; -, absent values.

Supplementary fig. S1. Phylogeny based on Maximum likelihood (ML) of COI-5P sequences. For the phylogeny, support values are listed as bootstrap for ML analyses and Bayesian posterior probabilities, respectively. Asterisks mark clades that are fully supported in both analyses. Newly generated sequences shown in bold. Scale bar refers to substitutions per site. Operational taxonomic units (OTU) described in this study are identified by a grey background.

Supplementary fig. S2. Phylogeny based on Maximum likelihood (ML) of SSU rDNA sequences. For the phylogeny, support values are listed as bootstrap for ML analyses and Bayesian posterior probabilities, respectively. Asterisks mark clades that are fully supported in both analyses. Newly generated sequences shown in bold. Scale bar refers to substitutions per site. Operational taxonomic units (OTU) described in this study are identified by a grey background.

Author contributions

L. M. Coutinho: original concept, molecular and morphological data, electron microscopy, analysis of molecular data, drafting and editing manuscript; F. P. Gomes: molecular and morphological data, phylogenetic analyses, drafting and editing manuscript; M. N. Sissini: molecular and morphological data, electron microscopy, drafting and editing manuscript; M. C. M. O. Henriques: molecular and morphological data; T. Vieira-Pinto: molecular and morphological data; M. C. de Oliveira: drafting and editing manuscript; P.A. Horta: drafting and editing manuscript; M.B. Barros-Barreto: original concept, analysis of molecular data, phylogenetic analyses, drafting and editing manuscript.

Additional information

Funding

This work was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. FAPESP (Biota 2013/11833–3), CNPq (301491/2013–5), Biota–FAPERJ (E–26/110.019/2011). LMC acknowledges a scholarship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). MCO acknowledges a CNPq fellowship (305687/2018-2). PH thanks TRH, CNPq, Protax, CAPES, PNADB, PELD ILOC, FAPESC and CAPES-PRINT financial support.