Anoles are highly visual animals, and there’s no display more visual than the extension of a dewlap. To understand how anoles use their colorful dewlaps to communicate, we must understand how anoles perceive color. Leo Fleishman of Union College has set out to do just that.
In his standing-room-only talk at SICB, Leo explained the need for a species’ dewlap to be easily distinguishable both from the dewlaps of other sympatric species, and from the background colors in the habitat. He described how his team quantifies dewlap color and natural habitat light conditions to determine how colors are differentiated by the anole visual system. One general finding that has emerged from these studies is that species in dark habitats have evolved lighter dewlaps, and those in brighter habitats have evolved darker dewlaps.
Leo also described how to differentiate anole visual signals using a color tetrahedron of anole perceptual color space. This tetrahedron is defined by the sensitivity of the four types of photoreceptors in anoles – cones that detect long wavelength, medium wavelength, short wavelength, and ultraviolet light. By plotting the spectral radiance of particular signals (for example, the dewlaps of two species) in the tetrahedron, you can determine how distinct two (or more) signals are in anole visual space. Further, this modeling approach allows us to determine the visibility of any dewlap in any environment!
Leo concluded his talk by describing one particularly cool way an anole can distinguish its dewlap in a low-light habitat: the translucent dewlaps of some species that seem to almost glow in deeply shaded forests. You can read more about these glowing dewlaps in a recent Open Access paper published in Functional Ecology by Fleishman and colleagues.