Allozyme and microsatellite loci provide discordant estimates of population differentiation in the endangered dusky grouper (Epinephelus marginatus) within the Mediterranean Sea

Authors

  • S. De Innocentiis,

    1. Department of Animal and Human Biology, University of Rome ‘La Sapienza’, Via. Borelli, 50, 00161 Rome, Italy,
    2. ICRAM, Central Institute for Marine Research, Via di Casalotti, 300, 00166 Rome, Italy,
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  • L. Sola,

    1. Department of Animal and Human Biology, University of Rome ‘La Sapienza’, Via. Borelli, 50, 00161 Rome, Italy,
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  • S. Cataudella,

    1. LESA, Experimental Ecology and Aquaculture Laboratory, University of Rome ‘Tor Vergata’, Via di Passolombardo, 430, 00133 Rome, Italy,
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  • P. Bentzen

    Corresponding author
    1. MMBL, Marine Molecular Biotechnology Laboratory, University of Washington, 3707 Brooklyn Avenue NE, 98105 Seattle, WA, USA
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P. Bentzen. ¶Present address: Biology Department, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1. Fax: + 1-902 4946899; E-mail: pbentzen@u.washington.edu

Abstract

The dusky grouper, Epinephelus marginatus, inhabits coastal reefs in the Mediterranean Sea and Atlantic Ocean. A decline in the abundance of this long-lived protogynous hermaphrodite has led to its listing as an endangered species in the Mediterranean, and heightened management concerns regarding its genetic variability and population substructure. To address these concerns, we analysed genetic variation at seven microsatellite and 28 allozyme loci in dusky groupers sampled from seven areas (for microsatellites) and three areas (for allozymes) in the west-central Mediterranean. Levels of genetic variability were higher for microsatellites than for allozymes (mean HE = 0.78 and 0.07, respectively), but similar to those observed in other marine fishes with comparable markers. Both microsatellites and allozymes revealed significant genetic differentiation among all areas analysed with each class of marker, but the magnitude of differentiation revealed by allozymes over three locales (FST = 0.214) was greater than that detected with microsatellites over seven areas, or over the three areas shared with the allozyme analysis (FST = 0.018 and ~0, respectively). A large proportion of the allozyme differentiation was due to a single locus (ADA*) possibly influenced by selection, but allozyme differentiation over the three areas was still highly significant (FST = 0.06, P < 0.0001), and the 95% confidence intervals for allozyme and microsatellite FST did not overlap when this locus was excluded. There was no evidence of isolation by distance with either class of markers. Our results lead us to conclude that dusky groupers are not panmictic in the Mediterranean Sea and suggest that they should be managed on a local basis. However, more work is needed to elucidate genetic relationships among populations.

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