Signal Evolution in an Invasive Species of Tropical Lizard, Anolis Distichus

The effectiveness of visual signals directly depends on the interaction between the signal being sent, the properties of the light illuminating the signal, and the background colors against which the signal is viewed. If the light conditions in an environment are changed, the design of a visual signal must also change in order to remain conspicuous. Signal adjustments of this type are imperative if the signalers are to be successful in a new environment, and can be the deciding factor in the ability of a species to spread into new areas. Anolis distichus is a tropical lizard recently introduced to Florida from the Bahamas and Hispaniola, and has spread to a wide variety of habitats throughout the state. Anoles use colorful throat fans called dewlaps to communicate, and Anolis distichus shows strong variation in dewlap color across its range in the Caribbean. Using a spectrophotometer, I measured the spectral properties of the light environments in different Anolis habitats in Florida, as well as the dewlaps of the Anolis distichus living in these different light environments. I found variation in the spectral quality and brightness of light available in the environments throughout South Florida. Concurrently, I also found widespread variation in dewlap color of the invasive anoles, including as many as five unique color expression patterns found among the different areas. As light properties in a given habitat will dictate the effectiveness of signal colors, this variation in dewlap color may be a result of variation in the lighting environment favoring specific dewlap colors. Ongoing work sets out to test this hypothesis by sampling throughout the expanding range of this invasive species in South Florida.