Date of Award

5-2019

Document Type

Thesis open access

Department

Biology

First Advisor

Michele A. Johnson

Second Advisor

Kira D. McEntire

Abstract

Organisms capable of physiological body color change can respond rapidly to changes in their social or external environment. Given that color change is often context-dependent, studying the role of color change can provide insights into how different organisms respond to and interact with their immediate environment. Currently there are three main hypotheses which explain the adaptive significance of rapid color change, including camouflage, social signaling, and thermoregulation. Green anoles, Anolis carolinensis, are one such species that use physiological color change to rapidly shift their dorsal body color from bright green to dark brown within seconds. Thus, they may use darkening and lightening of body color to either regulate their body temperature throughout the day, or as a visual signal during intraspecific communication. Previous studies have determined the physiological mechanisms by which color change occurs in green anoles, but few naturalistic studies have determined the ecological role of dynamic color change in anoles, and fewer still have examined how males and female green anoles may differentially use color change. In this thesis, I performed two studies testing two major hypotheses for the evolution of physiological color change. In my first study I examined the relationship between body color and body temperature of green anoles, and whether this varies between the sexes, or among different substrate types. My data showed that while males choose marginally warmer substrates and more exposed perch sites than females, there was no association between body color and body temperature in either sex. In the second study I tested whether body color is used in conjunction with behavioral displays of green anoles, and if this differs between the sexes. My results showed that overall, males are far more likely to be green than females. Further, males and females differ in how they use body color during social displays. In sum, my studies found that body color change is predominantly used in behavioral displays of green anoles, and males and females differ in how they use color during social signaling. My findings also indicate that thermoregulation is likely not a primary reason for body color change in either sex, and color likely plays less of a role in thermoregulation in anoles than previously believed.

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