Circumscription of Lithophyllum racemus (Corallinales, Rhodophyta) from the western Mediterranean Sea reveals the species Lithophyllum pseudoracemus sp. nov.

ABSTRACT

Species of the genus Lithophyllum are important carbonate producers and bioconstructors. In recent years, molecular studies focusing on this genus have unravelled several striking cases of cryptic and pseudocryptic diversity. Lithophyllum racemus is a common non-geniculate coralline alga-forming rhodoliths in the northeastern Atlantic Ocean and the Mediterranean Sea. Molecular phylogenies (psbA and coxI) reconstructed for some Mediterranean specimens morpho-anatomically assigned to L. racemus revealed two well-supported sister clades. Based on pairwise sequence divergences, we recognised these two clades as separate species, L. racemus and L. pseudoracemus sp. nov. The low number of specimens has not permitted any useful morpho-anatomical comparison between the species, and for now, only DNA sequencing permits separation. The discovery of L. pseudoracemus unravelled a new case of cryptic diversity in Mediterranean coralline algae, highlighting the substantially underestimated diversity of these seaweeds.

KEYWORDS:

• coxI
• Cryptic diversity
• DNA sequencing
• Morpho-anatomy
• psbA
• Rhodoliths
• Trichocytes

ACKNOWLEDGEMENTS

We are grateful to Enric Ballesteros, Carlo Cerrano, Saul Ciriaco, Diego Kurt-Kersting, Luisa Mangialajo, Florence Rousseau, Yannis Turpin and José Utge for sample collections. We thank the Marine Reserve of Columbretes Islands for providing permits and for field support. We also thank the captain, crew and scientific staff of the RV Minerva Uno for specimens collected during the STRATEGIA MARINA LIGURE-TIRRENO cruise. AC is grateful to Dr Roberto Arrigoni for his useful suggestions for the phylogenetic analyses. Christian Russo is acknowledged for assistance with laboratory work. Two anonymous reviewers and the Associate Editor Gavin Maneveldt are thanked for their comments, which helped to improve previous versions of the manuscript.

SUPPLEMENTARY MATERIAL

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Additional information

Funding

This work was supported by the Convenzione MATTM-CNR for the monitoring programmes carried out for the implementation of the Marine Strategy Framework Directive (MSFD, Art. 11, Dir. 2008/56/CE). Acquisition of some molecular data was carried out at the CNRS-UMS 2700 in Service de Systématique Moléculaire, MNHN, Paris with funds from the Action Transversale du Muséum National d’Histoire Naturelle and Port-Cros National Park. FR is grateful to the Università Politecnica delle Marche for financial support (Ricerca Scientifica di Ateneo, years 2017-2019).