Flower Color, Hummingbird Pollination, and Habitat Irradiance in Four Neotropical Forests1

Abstract

ABSTRACTPollinator visual systems differ considerably among broad groupings such as bees, bats, and birds, and it has been proposed that factors shaping the diversity of flower color in tropical plants include differences in pollinator perceptual abilities. Within the pollinators of the Neotropics, one major difference between taxa is that hummingbirds perceive color well across a broad range of wavelengths from 300–660 nm whereas most bees perceive color well over a narrower range spanning 300–550 nm. Thus, hummingbirds can see red and other long‐wavelength reflection much better than bees. Another factor that could potentially influence flower color in tropical forests is the difference in light availability among habitats such as gaps, canopy, and forest understory. I conducted a survey of floral color in four Neotropical forests using a portable spectroradiometer to provide an unbiased measure of color reflectance. The primary pollinator agents and light habitats of each plant species were classified using primary literature or accounts of direct observations by experts. Flower color was not influenced by differences in light availability between open and closed habitats but was influenced by pollinator visual systems. Specifically, insect flowers reflected across a broad range of the spectrum but hummingbird flowers reflected mostly long‐wavelength light (typically median wavelength <585 nm). Thus, hummingbird‐pollinated flowers are not tuned specifically to hummingbird color sensitivity but instead may decrease conspicuousness to bees and other insects that have poor visual sensitivity to long‐wavelength color.