Isolation by environmental distance in mobile marine species: molecular ecology of franciscana dolphins at their southern range

Authors

  • MARTIN MENDEZ,

    1. Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, MC5557, New York, NY 10027, USA
    2. Center for Conservation Genetics, Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
    3. Ocean Giants Program, Wildlife Conservation Society, 2300 Southern Blvd., Bronx, NY 10460-1099, USA
    4. Fundación AquaMarina, Del Sauce 748, Pinamar, Buenos Aires B7167BSN, Argentina
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  • HOWARD C. ROSENBAUM,

    1. Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, MC5557, New York, NY 10027, USA
    2. Center for Conservation Genetics, Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
    3. Ocean Giants Program, Wildlife Conservation Society, 2300 Southern Blvd., Bronx, NY 10460-1099, USA
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  • AJIT SUBRAMANIAM,

    1. Lamont Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964-1000, USA
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  • CHARLES YACKULIC,

    1. Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, MC5557, New York, NY 10027, USA
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  • PABLO BORDINO

    1. Fundación AquaMarina, Del Sauce 748, Pinamar, Buenos Aires B7167BSN, Argentina
    2. Wildlife Trust Alliance, 460 West 34th Street, New York, NY 10001, USA
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Martin Mendez, Fax: +1 212 769 5277; E-mail: mm1772@columbia.edu

Abstract

The assessment of population structure is a valuable tool for studying the ecology of endangered species and drafting conservation strategies. As we enhance our understanding about the structuring of natural populations, it becomes important that we also understand the processes behind these patterns. However, there are few rigorous assessments of the influence of environmental factors on genetic patterns in mobile marine species. Given their dispersal capabilities and localized habitat preferences, coastal cetaceans are adequate study species for evaluating environmental effects on marine population structure. The franciscana dolphin, a rare coastal cetacean endemic to the Western South Atlantic, was studied to examine these issues. We analysed genetic data from the mitochondrial DNA and 12 microsatellite markers for 275 franciscana samples utilizing frequency-based, maximum-likelihood and Bayesian algorithms to assess population structure and migration patterns. This information was combined with 10 years of remote sensing environmental data (chlorophyll concentration, water turbidity and surface temperature). Our analyses show the occurrence of genetically isolated populations within Argentina, in areas that are environmentally distinct. Combined evidence of genetic and environmental structure suggests that isolation by distance and a process here termed isolation by environmental distance can explain the observed correlations. Our approach elucidated important ecological and conservation aspects of franciscana dolphins, and has the potential to increase our understanding of ecological processes influencing genetic patterns in other marine species.

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