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ABSTRACT
Ulva is a green macroalgal genus with rich species diversity and worldwide distribution. While current knowledge on Ulva diversity focuses on temperate regions, genetic and morphological data in tropical and subtropical areas are scarce and the species richness is not clearly defined. The genus is known for its bloom-forming ability that can induce green tides leading to severe environmental and economic damage. In the last two decades, several important blooms of Ulva spp. have occurred in New Caledonia, requiring further investigations to identify the species involved. As knowledge of New Caledonian Ulva diversity is limited, an update to the Ulva spp. inventory in the area is essential. Based on Ulva specimens collected throughout New Caledonia (Grande Terre, Isle of Pines and Loyalty Islands), we (1) reassessed species diversity using species delimitation methods, (2) analysed morpho-anatomical characters to identify species and/or enrich their diagnosis, and (3) reconstructed a multilocus phylogeny (ITS, rbcL, tufA) of the genus. We found 21 secondary species hypotheses (SSHs) among our dataset, from which five were successfully assigned to U. lactuca, U. ohnoi, U. tepida, U. meridionalis and U. taeniata. Ten SSHs were defined as new species for which we provided taxonomic description, and six other SSHs were singletons that will need to be data-enriched for better interpretation. Our concatenated multilocus matrix included 61 Ulva species. Of these, 15 species were found in New Caledonia and were moderately to strongly supported. Among the Ulva species found in New Caledonia, seven are known to be bloom-forming which highlights the need for strict regulation and regular monitoring of water quality, particularly in areas exposed to strong nutrient input where these species can form green tides.
Highlights
Ulva diversity in New Caledonia was reassessed with 15 species highlighted.
Ten new species have been discovered in New Caledonia.
Indigenous species caused recent green tides in New Caledonia.
Acknowledgements
We would like to thank Marie-Alizée Douyère for the acquisition of some DNA sequences as well as Laurent Millet and Clarisse Majorel for their support and assistance. Molecular analyses were performed at the Plateforme du Vivant (CRESICA-IRD Noumea). We are also grateful to Francesca Benzoni and Lydiane Mattio for their help with Latin translations. We also thank Ricardo Rodolfo-Metalpa who inspired the name Ulva batuffolosa. We thank Jane Ballard for her useful comments to improve the manuscript and the English correction. Most of the samples came from the ELADE project and were collected by C.P, S.G., M.B., T.J. and S.V.W. Sampling authorizations were delivered by La Province Sud (No. 4406-2018/ARR/DENV). Other samples were collected during scientific campaigns described below: New Caledonia: Loyalty Islands, 2005: R/V Alis, BSM-LOYAUTE, 10.17600/5100030; Isle of Pines, 2001; 2005: R/V Alis, BIODIP, 10.17600/5100100; 2007: R/V Alis, CORALCAL-1, 10.17600/7100020; French Polynesia, 2008: Moorea-biocode; 2011: Marquises, Pakaihi i te Moana expedition; Papua New Guinea, 2012: R/V Alis, NUIGUINI campaign, 10.17600/12100070. Finally, we are very grateful to Serge Andréfouët, Mahé Dumas, Joseph Baly, Bernard Pelletier, Nicolas Job, Romain Le Gendre, Eric Chollet and Christophe Peignon for their opportunistic sampling, which has enriched the collection.
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/10.1080/09670262.2022.2027023
Supplementary table S1. List of the specimens included in this study, with sample IDs, species identification, location of sampling, GenBank accession numbers (or BOLD sequence ID in grey for those not submitted), and the corresponding SSH number, as well as the sequences used in the multilocus phylogeny.
Supplementary table S2. Primers used for amplification of the ITS, rbcL and tufA markers, corresponding DNA fragment size and references.
Supplementary table S3. PCR programs used according to the marker amplified.
Supplementary table S4. List of specimens from GenBank database included in our phylogenetic analyses, with voucher names, collection localities, sequence accession numbers for ITS, rbcL and tufA genes, and reference studies.
Supplementary table S5. Morpho-anatomical observations and measures of the specimens studied in each SSH.
Supplementary table S6. Decision aid to ascertain whether our tubular specimens correspond to new species or not: presence or absence of genetic data (0/1); if not, diagnosis found (x) and comparison of morphological characters; if not and in the last case, consultation of herbarium (x) to check external morphology. Arguments justifying our decision are also reported. NA: not attributable.
Supplementary figure S1. Maximum Clade Credibility Tree (MCCT) obtained from the BEAST analysis with the ITS dataset (unique haplotypes).
Supplementary figure S2. Maximum Clade Credibility Tree (MCCT) obtained from the BEAST analysis with the rbcL dataset (unique haplotypes).
Supplementary figure S3. Maximum Clade Credibility Tree (MCCT) obtained from the BEAST analysis with the tufA dataset (unique haplotypes).
Author contributions
L. Lagourgue: treatment and analyses of molecular data (species delimitation, phylogeny), morphological analyses, taxonomic diagnosis, original concept and drafting of manuscript; S. Gobin: samples collection, acquisition of genetic sequences, morphological observations; M. Brisset; samples collection, acquisition of genetic sequences and editing manuscript; S. Vandenberghe: acquisition of genetic sequences; C. Bonneville: acquisition of genetic sequences and editing manuscript; T. Jauffrais: samples collection and editing manuscript; S. Van Wynsberge: conception of the ELADE project, samples collection and editing manuscript. C.E. Payri: samples collection, morphological analyses, original concept and editing of manuscript.
