Pollinator behavior mediates negative interactions between two congeneric invasive plant species

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59 Scopus citations


Simultaneously flowering plant species may indirectly interact with each other by influencing the quantity of pollinator visitation and/or the quality of pollen that is transferred. These effects on pollination may depend on how pollinators respond to floral resources at multiple levels. In this study, we demonstrate pollinatormediated negative interactions between two invasive plants, Carduus acanthoides and Carduus nutans. Using constructed arrays of the two species, alone and in mixture, we quantified pollinator visitation at the patch and individual plant levels and measured seed production. We found that co-occurrence of our species led to a shift in pollinator services at both levels. Greater interference occurred when arrays were small and spacings between neighboring plants were large. Aspatially explicit movement model suggests that pollinator foraging behavior, which mediates the interactions between plants, was driven by floral display size rather than species identity per se. Pollinator behavior significantly reduced the proportion of seed set for both species relative to that in single-species arrays. Overall, the dependence of pollinator behavior on patch size, spacing between plants, and patch composition can lead to pollinator-mediated plant interactions that range from facilitative to competitive.

Original languageEnglish (US)
Pages (from-to)110-118
Number of pages9
JournalAmerican Naturalist
Issue number1
StatePublished - Jan 2011

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics


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