Gorgonian species show a high morphological variability in relation to the environment in which they live. In coastal areas, parameters such as temperature, light, currents, and food availability vary significantly with depth, potentially affecting morphology of the colonies and the structure of the populations, as well as their connectivity patterns. In tropical seas, the existence of connectivity between shallow and deep populations supported the hypothesis that the deep coral reefs could potentially act as (reproductive) refugia fostering re-colonization of shallow areas after mortality events. Moreover, this hypothesis is not so clear accepted in temperate seas. Eunicella singularis is one of the most common gorgonian species in Northwestern Mediterranean Sea, playing an important role as ecosystem engineer by providing biomass and complexity to the coralligenous habitats. It has a wide bathymetric distribution ranging from about 10 m to 100 m. Two depth-related morphotypes have been identified, differing in colony morphology, sclerite size and shape, and occurrence of symbiotic algae, but not in mitochondrial DNA haplotypes. In the present study the genetic structure of E. singularis populations along a horizontal and bathymetric gradient was assessed using microsatellites and ITS1 sequences. Restricted gene flow was found at 30–40 m depth between the two Eunicella morphotypes. Conversely, no genetic structuring has been found among shallow water populations within a spatial scale of ten kilometers. The break in gene flow between shallow and deep populations contributes to explain the morphological variability observed at different depths. Moreover, the limited vertical connectivity hinted that the refugia hypothesis does not apply to E. singularis. Re-colonization of shallow water populations, occasionally affected by mass mortality events, should then be mainly fueled by larvae from other shallow water populations.
Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA) & Centro Interdipartimentale di Ricerca per le Scienze Ambientali (CIRSA), University of Bologna, CoNISMa, Via S. Alberto 163, I-48123, Ravenna, Italy;Departament d’Ecología, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain;Institut de Ciències del Mar–CSIC, Pg. Maritim de la Barceloneta 37–49, 08003, Barcelona, Spain;Biodiversidad y Ecología de Invertebrados Marinos, Departamento de Zoología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6, 41012, Sevilla, Spain;Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Ecogéochimie des Environnements Benthiques (LECOB), Observatoire Océanologique, 66650, Banyuls sur Mer, France;Institut de Ciència i Tecnologia Ambientals, Universitat Auntònoma de Barcelona, Cerdanyola del Vallés, Spain;Institut de Ciències del Mar–CSIC, Pg. Maritim de la Barceloneta 37–49, 08003, Barcelona, Spain;Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA) & Centro Interdipartimentale di Ricerca per le Scienze Ambientali (CIRSA), University of Bologna, CoNISMa, Via S. Alberto 163, I-48123, Ravenna, Italy;Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine, ISMAR, Bologna, Italy
Recommended Citation:
Federica Costantini,Andrea Gori,Pablo Lopez-González,et al. Limited Genetic Connectivity between Gorgonian Morphotypes along a Depth Gradient[J]. PLOS ONE,2016-01-01,11(8)