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13 December 2021 The Effects of Flower Patch Density on Pollinator Visitation
Tristan A. Barley, Michael G. Martinez Algarin, Jonathan T. Bauer
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There is conflicting research regarding how conspecific plant density can affect pollinator visitation, with some studies indicating dense flower patches will receive more visitors and other studies demonstrating the opposite. This study investigated the effects of conspecific density on pollinator visitation in a restored prairie. Three plant species, Penstemon digitalis (Nutt. ex Sims) (Lamiales: Plantaginaceae), Monarda fistulosa (L.) (Lamiales: Lamiaceae), and Eryngium yuccifolium (Michx.) (Apiales: Apiaceae), were observed, with visiting pollinators recorded. Conspecific density did not have an effect on total pollinator visitation rates for any of the focal plant species. However, different groups of pollinators varied in their responses to flower density, notably with larger Bombus spp. tending to visit dense flowering patches more than did other groups of bees. This suggests that plant density may impact certain pollinators differently than others. These results also indicate a possible mechanism through which multiple pollinator species can coexist while only one flowering resource is available, with the foraging behavior of smaller bees potentially allowing them to avoid competition with larger, social bees. Furthermore, a comparison of seed weight demonstrated that E. yuccifolium plants tended to have larger seed sets in isolated individuals, suggesting that flowers in large patches may be pollinated less effectively and are competing for, rather than facilitating, pollinator visits.

© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail:
Tristan A. Barley, Michael G. Martinez Algarin, and Jonathan T. Bauer "The Effects of Flower Patch Density on Pollinator Visitation," Environmental Entomology 51(2), 482-491, (13 December 2021).
Received: 10 June 2021; Accepted: 17 November 2021; Published: 13 December 2021

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plant–pollinator interaction
restored prairie
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