Molecular genetic diversity of seaweeds morphologically related to Ulva rigida at three sites along the French Atlantic coast

Manon Dartois; Eric Pante; Amélia Viricel; Vanessa Becquet; Pierre-Guy Sauriau

doi:10.7717/peerj.11966

Molecular genetic diversity of seaweeds morphologically related to Ulva rigida at three sites along the French Atlantic coast

PeerJ. 2021 Dec 24:9:e11966. doi: 10.7717/peerj.11966. eCollection 2021.

Authors

Manon Dartois¹, Eric Pante^{1

2}, Amélia Viricel¹, Vanessa Becquet¹, Pierre-Guy Sauriau¹

Affiliations

¹ Littoral, Environnement et Sociétés, UMR 7266, CNRS - La Rochelle Université, La Rochelle, France.
² Institut Systématique Evolution Biodiversité (ISYEB), CNRS, Sorbonne Université, EPHE, Université des Antilles, Museum national d'Histoire naturelle, Paris, France.

Abstract

Foliose species of the genus Ulva are notoriously difficult to identify due to their variable morphological characteristics and high phenotypic plasticity. We reassessed the taxonomic status of several distromatic foliose Ulva spp., morphologically related to Ulva rigida, using DNA barcoding with the chloroplastic tufA and rbcL (for a subset of taxa) genes for 339 selected attached Ulva specimens collected from three intertidal rocky sites. Two of the collection sites were in Brittany and one site was in Vendée, along the Atlantic coast of France. Molecular analyses included several museum specimens and the holotype of Ulva armoricana Dion, Reviers & Coat. We identified five different tufA haplotypes using a combination of phylogenetic analysis, with the support of several recently sequenced holotypes and lectotypes, and a species delimitation method based on hierarchical clustering. Four haplotypes were supported by validly named species: Ulva australis Areschoug, Ulva fenestrata Postels & Ruprecht, Ulva lacinulata (Kützing) Wittrock and U. rigida C. Agardh. The later was additionally investigated using rbcL. The fifth haplotype represented exact sequence matches to an unnamed species from European Atlantic coasts. Our results support: (1) the synonymy of both U. rigida sensu Bliding non C. Agardh and U. armoricana with U. lacinulata. This finding is based on current genetic analysis of tufA from the U. armoricana holotype and recent molecular characterization of the lectotype of U. laetevirens, which is synonymous to U. australis, (2) the presence of U. australis as a misidentified introduced species in Brittany, and (3) the presence of U. fenestrata and U. rigida in southern Brittany. The taxonomic history of each species is discussed, highlighting issues within distromatic foliose taxa of the genus Ulva and the need to genetically characterize all its available type specimens.

Keywords: Algal bloom; DNA barcoding; Green tides; Herbarium; Integrative taxonomy; Phenotypic plasticity; Pseudo-cryptic species; Species delimitation; Ulva spp.; tufA.

Grants and funding

This research was supported by the CNRS, La Rochelle Université, Parc naturel régional du Marais poitevin (contract 180166-04/04/2018), the project DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing good Environmental Status, FP7, grant no. 308392), and the project ECONAT funded by the Contrat de Plan Etat-Région, CNRS and the European Regional Development Fund (FEDER). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.