Passive larval transport explains recent gene flow in a Mediterranean gorgonian
Understanding the patterns of connectivity is required by the Strategic Plan for Biodiversity 2011–2020 and will be used to guide the extension of marine protection measures. Despite the increasing accuracy of ocean circulation modelling, the capacity to model the population connectivity of sessile benthic species with dispersal larval stages can be limited due to the potential effect of filters acting before or after dispersal, which modulates offspring release or settlement, respectively. We applied an interdisciplinary approach that combined demographic surveys, genetic methods (assignment tests and coalescent-based analyses) and larval transport simulations to test the relative importance of demographics and ocean currents in shaping the recent patterns of gene flow among populations of a Mediterranean gorgonian (Eunicella singularis) in a fragmented rocky habitat (Gulf of Lion, NW Mediterranean Sea). We show that larval transport is a dominant driver of recent gene flow among the populations, and significant correlations were found between recent gene flow and larval transport during an average single dispersal event when the pelagic larval durations (PLDs) ranged from 7 to 14 d. Our results suggest that PLDs that efficiently connect populations distributed over a fragmented habitat are filtered by the habitat layout within the species competency period. Moreover, a PLD ranging from 7 to 14 d is sufficient to connect the fragmented rocky substrate of the Gulf of Lion. The rocky areas located in the centre of the Gulf of Lion, which are currently not protected, were identified as essential hubs for the distribution of migrants in the region. We encourage the use of a range of PLDs instead of a single value when estimating larval transport with biophysical models to identify potential connectivity patterns among a network of Marine Protected Areas or even solely a seascape.
KeywordsMarine connectivity Pelagic larval duration Genetic structure Marine Protected Areas Hydrodynamic model Gulf of Lion
This work was (co-) funded through a MARES Grant. MARES is a Joint Doctorate programme selected under Erasmus Mundus coordinated by Ghent University (FPA 2011-0016). Check www.mares-eu.org for additional information. This work was also partially funded by the French National Program LITEAU IV of the Ministère de l’Ecologie et de l’Environnement Durable under project RocConnect—Connectivité des habitats rocheux fragmentés du Golfe du Lion (PI, K. Guizien, Project Number 12-MUTS-LITEAU-1-CDS-013. The authors particularly thank the scientific managers of the Gulf of Lion MPA: S. Blouet, E. Charbonnel, B. Ferrari and J. Payrot for valuable interactions during the study design. The authors gratefully acknowledge the helpful assistance during sampling of R. Bricout, F. Cornette, S. Fanfard, B. Hesse, C. Labrune, L. Lescure, J.-C. Roca, P. Romans, and the staff of the Réserve Naturelle Marine de Cerbère-Banyuls, Aire Marine Protégée Agatoise, Parc Naturel Marin du Golfe du Lion and Parc Marin de la Côte Bleue. We also acknowledge American Journal Experts for English editing service.
MP, LB, and KG designed the study. SB performed all the laboratory work. MP, FC and KG analysed all the data. All authors contributed to the writing of the manuscript.
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