Maggie M. Reddy1,2, Stéphane Greff3, Molly McCann2, John. J. Bolton3, Olivier P. Thomas2
1 Department of Biological Sciences, University of Cape Town, South Africa
2 Marine Biodiscovery, School of Biological and Chemical Sciences and Ryan Institute, National University of Ireland Galway, Ireland
3 Institut Méditerranéen de Biodiversité et d’Ecologie Marine et Continentale (IMBE), UMR 7263 CNRS, IRD, Aix Marseille Université, Avignon Université, Station Marine d’Endoume, rue de la Batterie des Lions, Marseille, France
Kelp forests are among the most productive ecosystems in our oceans, supporting biodiverse and commercially important species. The only major kelp forest in Sub-Saharan Africa occurs in southern Africa, where these habitats are formed largely by species of Laminaria and Ecklonia. Two species of Ecklonia are widespread, with E. maxima dominant along cool temperate coastlines to the west, and E. radiata along warm temperate regions to the east, including nearby offshore reefs. More recently, an “Ecklonia contact zone” has formed at the southern tip of Africa, following a recent eastward shift in the range of E. maxima. The aim of the present study was to elucidate the chemical and genetic diversity of E. maxima and E. radiata in southern Africa and to determine whether these two species hybridize. This was achieved by using a combined metabolomic and DNA approach applied to populations of Ecklonia collected from throughout its known distribution range in southern Africa spanning roughly 3500 km of coastline. We used untargeted metabolomics by LC-MS/MS and cox1, with an additional gene applied to the potential hybrids, to estimate the overall chemical and genetic diversity respectively. Our data largely resolved distinct biogeographic groups within each species and supported a third distinct group intermediate between E. maxima and E. radiata. The combined metabolomic and DNA approach was powerful in elucidating patterns of diversity and structure in Ecklonia along this dynamic coastline. We believe that such information can help guide MPA planning and management of these species in the future.