Pollinator preferences were observed for the six species of section Erythranthe of the genus Mimulus using greenhouse-grown plants placed in a meadow in the Red Butte Canyon Natural Area, Salt Lake County, Utah. The principal pollinators were hummingbirds and bumble bees. Hummingbirds preferred the species with the most reflexed tubular flowers regardless of color, whereas bumblebees preferred pink. lavender, or yellow flowers to red flowers regardless of shape. Results for the six species were confirmed by observations of F2 hybrid recombinant plants selected such that flower color could be held constant and flower shape varied and vice versa.
Sutherland, Steven D. and Vickery, Robert K. Jr.
"On the relative importance of floral color, shape, and nectar rewards in attracting pollinators to Mimulus,"
Great Basin Naturalist: Vol. 53
, Article 2.
Available at: http://scholarsarchive.byu.edu/gbn/vol53/iss2/2