Advertisement

Implications of isolation and low genetic diversity in peripheral populations of an amphi-Atlantic coral

Authors

  • F. NUNES,

    1. Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive MC 0208, La Jolla, CA 92093-0208, USA
    Search for more papers by this author
  • R. D. NORRIS,

    1. Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive MC 0208, La Jolla, CA 92093-0208, USA
    Search for more papers by this author
  • N. KNOWLTON

    1. Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive MC 0208, La Jolla, CA 92093-0208, USA
    2. National Museum of Natural History, Smithsonian Institution, Washington, DC 20012, USA
    Search for more papers by this author

  • Dr Nunes is interested in the evolution and phylogeography of corals and reef organisms. She has recently obtained her doctoral degree at Scripps Institution of Oceanography. Dr Norris is a Professor of Paleontology at SIO and is interested in the structure and dynamics of large-scale diversification in the history of life. Dr Knowlton’s research focuses on ecology, evolution and conservation of coral reef organisms. Her analyses have led to the now widespread recognition that estimates of marine biodiversity are probably too low by a factor of ten.

Flavia Nunes, Fax: 858-822-3310; E-mail: fnunes@ucsd.edu

Abstract

Limited dispersal and connectivity in marine organisms can have negative fitness effects in populations that are small and isolated, but reduced genetic exchange may also promote the potential for local adaptation. Here, we compare the levels of genetic diversity and connectivity in the coral Montastraea cavernosa among both central and peripheral populations throughout its range in the Atlantic. Genetic data from one mitochondrial and two nuclear loci in 191 individuals show that M. cavernosa is subdivided into three genetically distinct regions in the Atlantic: Caribbean-North Atlantic, Western South Atlantic (Brazil) and Eastern Tropical Atlantic (West Africa). Within each region, populations have similar allele frequencies and levels of genetic diversity; indeed, no significant differentiation was found between populations separated by as much as 3000 km, suggesting that this coral species has the ability to disperse over large distances. Gene flow within regions does not, however, translate into connectivity across the entire Atlantic. Instead, substantial differences in allele frequencies across regions suggest that genetic exchange is infrequent between the Caribbean, Brazil and West Africa. Furthermore, markedly lower levels of genetic diversity are observed in the Brazilian and West African populations. Genetic diversity and connectivity may contribute to the resilience of a coral population to disturbance. Isolated peripheral populations may be more vulnerable to human impacts, disease or climate change relative to those in the genetically diverse Caribbean-North Atlantic region.

Ancillary