Testing the genetic predictions of a biogeographical model in a dominant endemic Eastern Pacific coral (Porites panamensis) using a genetic seascape approach

Authors

  • Nancy C. Saavedra-Sotelo,

    1. Laboratorio de Ecología Molecular, Departamento de Oceanografía Biológica, CICESE, Baja California, México
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  • Luis E. Calderon-Aguilera,

    1. Laboratorio de Ecología y Pesquerías de la Zona Costera, Departamento de Ecología Marina, CICESE, Baja California, México
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  • Héctor Reyes-Bonilla,

    1. Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, Baja California Sur, México
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  • David A. Paz-García,

    1. Laboratorio de Genética para la Conservación, Centro de Investigaciones Biológicas del Noroeste, Baja California Sur, México
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  • Ramón A. López-Pérez,

    1. Laboratorio de Ecosistemas Costeros, Departamento de Hidrobiología, UAM-Iztapalapa, Distrito Federal, México
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  • Amilcar Cupul-Magaña,

    1. Departamento de Ciencias Biológicas, Centro Universitario de la Costa, Universidad de Guadalajara, Jalisco, México
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  • José A. Cruz-Barraza,

    1. Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México (Unidad Académica Mazatlán), Sinaloa, México
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  • Axayácatl Rocha-Olivares

    Corresponding author
    1. Laboratorio de Ecología Molecular, Departamento de Oceanografía Biológica, CICESE, Baja California, México
    • Correspondence

      Axayácatl Rocha-Olivares, Biological Oceanography Department, CICESE, Carretera Ensenada-Tijuana 3918, Ensenada, Baja California, C.P. 22860, México. Tel: + 646-1750544; Fax: + 646-1750545; E-mail: arocha@cicese.mx

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Abstract

The coral fauna of the Eastern Tropical Pacific (ETP) is depauperate and peripheral; hence, it has drawn attention to the factors allowing its survival. Here, we use a genetic seascape approach and ecological niche modeling to unravel the environmental factors correlating with the genetic variation of Porites panamensis, a hermatypic coral endemic to the ETP. Specifically, we test if levels of diversity and connectivity are higher among abundant than among depauperate populations, as expected by a geographically relaxed version of the Abundant Center Hypothesis (rel-ACH). Unlike the original ACH, referring to a geographical center of distribution of maximal abundance, the rel-ACH refers only to a center of maximum abundance, irrespective of its geographic position. The patterns of relative abundance of P. panamensis in the Mexican Pacific revealed that northern populations from Baja California represent its center of abundance; and southern depauperate populations along the continental margin are peripheral relative to it. Genetic patterns of diversity and structure of nuclear DNA sequences (ribosomal DNA and a single copy open reading frame) and five alloenzymatic loci partially agreed with rel-ACH predictions. We found higher diversity levels in peninsular populations and significant differentiation between peninsular and continental colonies. In addition, continental populations showed higher levels of differentiation and lower connectivity than peninsular populations in the absence of isolation by distance in each region. Some discrepancies with model expectations may relate to the influence of significant habitat discontinuities in the face of limited dispersal potential. Environmental data analyses and niche modeling allowed us to identify temperature, water clarity, and substrate availability as the main factors correlating with patterns of abundance, genetic diversity, and structure, which may hold the key to the survival of P. panamensis in the face of widespread environmental degradation.

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