|Dunne, Rick -|
Submitted to: American Midland Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2013
Publication Date: N/A
Interpretive Summary: Red tubular flowers represent the textbook example of evolutionary convergence on one particular kind of pollinator, hummingbirds. It is thought that such adaptations favor hummingbirds as pollinators while excluding presumably ineffective pollinators, such as bees. Inasmuch as hummingbirds are not agricultural pollinators, growing such "hummingbird" flowers as Penstemon eatonii for horticultural and restoraiton seed would be problematic. However, we report that generalist bees alone (Apis. Anthophora) consistently generated massive seed yields by P. eatonii that was being farmed for restoration seed production. Apparently, derived floral traits that attract and position foraging hummingbirds (red deeply tubular flowers and abundant dilute nectar) need not compromise pollination by generalist bees.
Technical Abstract: The red tubular flowers of Penstemon eatonii (Plantaginaceae, formerly Scrophulariaceae) conform to the classic pollination syndrome for hummingbirds. This could be problematic when farming this wildflower for rangeland restoration seed. By some models and experiments with nectaring bumblebees at P. barbatus, bees took floral rewards without pollinating such an omithophilous flowers. Conversely, recent studies with Dudleya (Crassulaceae) conclude that specialization on hummingbirds need not incur trade-offs for pollination by generalist bees. We report that generalist bees alone (Apis, Anthophora) consistently generated massive seed yields by P. eatonii that was being farmed for restoration seed production. Behavioral and morphological considerations suggest two subclasses of Penstemon with red tubular flowers; those like P. eatonii retain adaptations to utilize generalist (but not specialist) bees as pollinators. Derived floral traits that attract and position foraging hummingbirds (red deeply tubular flowers and abundant dilute nectar) need not compromise pollination by generalist bees.