How do plants balance multiple mutualists? Correlations among traits for attracting protective bodyguards and pollinators in cotton (Gossypium)
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Many species, both plants and animals, are simultaneously engaged in interactions with multiple mutualists. However, the extent to which separate traits that attract different mutualist guilds display negative or positive relationships remains largely unstudied. We asked whether correlations exist among extrafloral nectary traits to attract arthropod bodyguards and floral traits to attract pollinator mutualists. For 37 species in the cotton genus (Gossypium), we evaluated correlations among six extrafloral nectary traits and four floral traits in a common greenhouse environment, with and without correction for phylogenetic non-independence. Across Gossypium species, greater investment in extrafloral nectary traits was positively correlated with greater investment in floral traits. Positive correlations remained after accounting for the evolutionary history of the clade. Our results demonstrate that traits to maintain multiple mutualist guilds can be positively correlated across related species and build a more general understanding of the constraints on trait evolution in plants.
KeywordsAnt Extrafloral nectar Evolutionary constraint Floral nectar Mutualism Trade-off
We thank J. Frelichowski and J. Love for facilitating research at the USDA Southern Plains Agricultural Research Center. J. Wendel advised on construction of the Gossypium phylogeny for use in phylogenetically independent contrasts. L. Seifert, L. Albert, and R. Ross collected data in greenhouses. R. Anwar and A. Gorischek provided laboratory assistance. J.A.R. was supported by the Godwin Assistant Professorship at Rice University.
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