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Abstract
Mattio L., Zubia M., Loveday B, Crochelet E., Duong N., Payri C.E., Bhagooli R. and Bolton J.J. 2013. Sargassum (Fucales, Phaeophyceae) in Mauritius and Réunion, western Indian Ocean: taxonomic revision and biogeography using hydrodynamic dispersal models. Phycologia 52: 578–594. DOI: 10.2216/13-150.1
Mauritius and Réunion are part of the Mascarene Islands situated in the southwestern Indian Ocean, c. 800 km east of Madagascar. A total of 44 different Sargassum species and subspecific taxa was listed in the literature for these islands. This was a remarkable number for such isolated and small islands, and was more than have been recorded from Madagascar or other East African countries. The first aim of our study was to revise these species lists using newly collected specimens to provide a reliable and illustrated tool for the identification of the Mauritian and Réunion Sargassum. On the basis of morphological and molecular analyses, a total of six taxa was identified as S. cymosum f. borbonicum, S. obovatum, S. pfeifferae (reinstated), S. polycystum, S. portierianum and S. robillardii (stat. nov.). A seventh taxon, S. scopula, was identified from a herbarium collection but not re-collected. As a result of our taxonomic revision, we concluded that most of the species listed in the literature for both Mauritius and Réunion were misidentifications or synonyms, and we proposed three new taxonomic synonyms. The biogeography of the six Sargassum taxa was further investigated using local and regional hydrodynamic dispersal models. Results underlined the isolated position of the Mascarene Islands with (1) unlikely import of Sargassum in present-day conditions, (2) likely dispersal/exchanges within the archipelago and (3) a two-pronged export of Sargassum to the east coast of Madagascar and the Seychelles with a major stream northwestward and a weaker stream southwestward. These oceanic conditions had probably shaped the Sargassum diversity of the Mascarene Islands and in particular explained the endemicity of S. cymosum f. borbonicum and restricted distribution of S. obovatum, S. pfeifferae, S. robillardii and S. scopula.
ACKNOWLEDGEMENTS
The staff members of the Department of Biosciences of the University of Mauritius are warmly thanked for their help in the field in Mauritius. We also thank the University of Mauritius for the opportunity to jointly organise a ‘Seaweed Biodiversity and Biogeography’ workshop at the University of Mauritius. The authors are thankful to the Government of Mauritius for granting clearance for the workshop and collection of samples around Mauritius Island. Many thanks to Dr Claudia Baider from the Mauritius Herbarium (R.E. Vaughan Building, Agricultural Services, Ministry of Agro-Industry and Food Security) for her help with herbarium collections. Part of the project was funded by the National Research Foundation (South Africa) and the University of Cape Town. The BIOLAVE expedition in Réunion was managed by ARVAM and funded by Délégation Régionale à la Recherche et à la Technologie, Direction de l'Environnement, de l'Aménagement et du Logement, and Fond Européen de DEveloppement Régional. Liana Swart of the DNA Sequencer (University of Stellenbosch) is warmly thanked for processing the Mauritius samples. Many thanks to F. Leliaert for sending scans of the specimens kept in the Ghent Phycology Herbarium. The following curators are also greatly acknowledged for their help in searching for additional type specimens: A. Igersheim (W), N. Lundholm and I. Friis (C), C. Nepi (FI), R. Marcucci (PAD), L. Amadei (PI). L.M. post-doc is funded by Marine Research Institute (University of Cape Town). B.L. acknowledges funding from the European Community's Seventh Framework Programme FP7/2007-2013-Marie-Curie Initial Training Networks (grant agreement 238512: GATEWAYS project). Part of the model analyses were run at the Department for Science and Technology/Council for Scientific and Industrial Research, Centre for High Performance Computing, Cape Town. Finally, we thank the reviewers who provided useful comments for the revision of the manuscript.
SUPPLEMENTARY DATA
Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/13-150.1.s1.