Hollace Yeary, 2009

Kent State University

Are plant-pollinator interactions mediated by defensive chemistry?

Megachile rotundata larvae were reared on the pollen of three members of the Solanaceae family (Physalis longifolia, Solanum dulcamara, and Datura stramonium) in order to ascertain whether these plants chemically protect their pollen. This plant family has substantial quantities of alkaloids in foliage that deter most generalist species of herbivores, and it is unknown how alkaloid abundance changes from foliar to floral tissues. M. roundata were also reared on the pollen of Coronilla varia, a member of the Fabaceae family, and known host plant to Megachile. We predicted that if plants visited primarily by specialist pollinators are chemically protecting their pollen from generalists, then Megachile rotundata larvae would be unable to develop on the pollen of Physalis longifolia, but able to develop on Solanum dulcamara. Because Datura stramonium temporally limits visitation, it was not an obvious prediction whether M. rotundata would be able to develop on its pollen. No significant differences were found among treatment groups regarding development time, larval weight, and survivorship. This study concludes that these plants do not contain toxic compounds in concentrations sufficient to deter visitation by pollinators not accustomed to visiting these plants, and that other mechanisms determine visitation breadth in plant-pollinator interactions. To what degree plant characteristics and bee phylogeny may affect the foraging choices of pollinators is considered.


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