Meeting Abstract
Anolis lizards communicate with colorful throat fans known as dewlaps. Dewlaps come in a wide variety of colors and our research has focused on trying to explain the evolution of this diversity. We assume that dewlap colors have evolved that are (1) easy for lizards to distinguish from those of sympatric species and (2) are easily distinguished from other natural color patches in the habitat. In order to assess how different colors and different habitat light conditions impact signal color visibility we need to know how distant different colors are in anoline perceptual color space. We know a great deal about the physiology and anatomy of the anoline visual system and can use this knowledge to test different models of distance in perceptual color space. We have also developed two different behavioral assays of color discrimination based on (1) attention responses and (2) food choice, that allow us to test the efficacy of different sensory-system based models. We have found that photoreceptor-noise models, and simpler models based on distance in tetrachromatic color space, both give accurate predictions of response to differences in color stimuli. Using both models and behavior we are currently investigating the impact of low light levels on color discrimination tasks. Our initial results suggest that under shaded forest conditions, distances in perceptual space are reduced, and many species from these habitats have evolved mechanisms to increase the total intensity of light emitting from their dewlaps. One impressive mechanism is the incorporation of transmitted light to create a translucent dewlap that appears to glow. This increase in total light intensity increases the reliability of perception of the dewlap color in low light habitats.
