Retention of mutualism in a geographically diverging interaction

Authors

  • John N. Thompson,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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  • Anna-Liisa Laine,

    1. Metapopulation Research Group, Department of Biological and Environmental Sciences, University of Helsinki, PO Box 65 (Viikinkaari 1), FI-00014 Helsinki, Finland
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  • Jill F. Thompson

    1. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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Correspondence: E-mail:thompson@biology.ucsc.edu

Abstract

Ecology Letters (2010) 13: 1368–1377

Abstract

A current challenge in coevolutionary biology is to understand how interactions between pairs of species change as they diversify into multispecific interactions. We tested whether the previously demonstrated pairwise mutualism between the widespread pollinating floral parasite Greya politella and its Lithophragma hostplants is ecologically enhanced or diminished in a region in which another Greya species, Greya obscura, uses the same host, Lithophragma cymbalaria. Field surveys and experimental trials showed that pollination efficacy by G. politella was more than an order of magnitude higher than by G. obscura, but G. politella abundance varied greatly between years. Greya obscura had a strongly positive effect on seed set in a year when G. politella densities were exceptionally low. Our results suggest that the coevolving mutualism between Greya and Lithophragma has potentially been enhanced rather than diminished as this interaction has diversified in the number of pollinating Greya species.

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