Kimball, Sarah .
Floral Visitors of Penstemon Hybrids Along an Elevational Gradient.
Hybrid zones can form when two species of plants hybridize along an environmental gradient. Changes in floral morphology across such a gradient can be influenced by pollinator behavior. Pollinators may prefer one species, may prefer the habitat of one species, or may be less effective at transferring pollen to or from one of the species. I studied the gradual change in morphology and nectar production of Penstemon newberryi, P. davidsonii, and their hybrids along an elevational gradient in the Sierra Nevada of California. Morphological measurements were used to construct a hybrid index. I also observed floral visitors along the gradient and performed an ordination to determine whether the pollinator community changed along with plant morphology. Plants varied in a clinal pattern along the elevational gradient. Sixty-seven floral visitors were observed visiting plants. The variation in the visitor community was incremental, although visitors to Penstemon davidsonii were separated from those to P. newberryi and hybrids along the main ordination axis. Hummingbirds were only found at low and middle elevations, and small Halictid bees were relatively more abundant at high elevations. It is unclear whether the floral visitors are responding to a change in plants or to a change in elevation. These hypotheses could be separated with preference experiments.
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1 - University of California Irvine, Department of Ecology & Evolutionary Biology, 321 Steinhaus Hall, Irvine, California, 92697-2525, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:30 AM