Ecological selection maintains cytonuclear incompatibilities in hybridizing sunflowers

Authors

  • Julianno B. M. Sambatti,

    1. Department of Botany, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada V6T 1Z4
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    • These authors contributed equally to this work.

  • Daniel Ortiz-Barrientos,

    Corresponding author
    1. Department of Botany, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada V6T 1Z4
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    • These authors contributed equally to this work.

  • Eric J. Baack,

    1. Department of Botany, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada V6T 1Z4
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    • Present address: Department of Biology, Luther College, 700 College Drive, Decorah, IA 52101, USA.

  • Loren H. Rieseberg

    1. Department of Botany, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada V6T 1Z4
    2. Department of Biology, Indiana University, 1001 East Third Street Bloomington, IN 47405-3700, USA
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*Correspondence and present address: School of Integrative Biology, The University of Queensland, Goddard Building (8) R120, St Lucia. Brisbane, Qld 4072, Australia. E-mail: d.ortizbarrientos@uq.edu.au

Abstract

Despite the recent renaissance in studies of ecological speciation, the connection between ecological selection and the evolution of reproductive isolation remains tenuous. We tested whether habitat adaptation of cytoplasmic genomes contributes to the maintenance of reproductive barriers in hybridizing sunflower species, Helianthus annuus and Helianthus petiolaris. We transplanted genotypes of the parental species, reciprocal F1 hybrids and all eight possible backcross combinations of nuclear and cytoplasmic genomes into the contrasting xeric and mesic habitats of the parental species. Analysis of survivorship across two growing seasons revealed that the parental species’ cytoplasms were strongly locally adapted and that cytonuclear interactions (CNIs) significantly affected the fitness and architecture of hybrid plants. A significant fraction of the CNIs have transgenerational effects, perhaps due to divergence in imprinting patterns. Our results suggest a common means by which ecological selection may contribute to speciation and have significant implications for the persistence of hybridizing species.

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