Generalist Bees Pollinate Red-flowered Penstemon eatonii: Duality in the Hummingbird Pollination Syndrome
2014
Cane, James H. | Dunne, Rick
The red tubular flowers of Penstemon eatonii (Plantaginaceae) typify the classic pollination syndrome for hummingbirds. Bees are thought to diminish its seed siring potential, but we found that foraging female generalist bees (Apis, Anthophora) deposited substantial amounts of conspecific pollen on P. eatonii stigmas. In the absence of hummingbirds, bee pollination of cultivated P. eatonii annually generated massive seed yields from a 1.5 ha field. Most penstemons with red tubular flowers like P. eatonii present a symmetrically flared floral opening that facilitates landing by foraging bees. Derived floral traits that attract and position nectar-foraging hummingbirds for efficient pollen export (red deeply tubular flowers secreting abundant dilute nectar) need not compromise pollination and seed production that result from visitation by generalist bees seeking pollen and/or nectar.
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