DISSERTATION RESEARCH: The Function and Evolution of Rapid Color Change as a Social Signal

Arizona State University, Scottsdale AZ

Investigators

Abstract

To date, most studies on visual signals have focused on the fixed appearances of animals and, specifically, of their color. As a result, dynamic color signals remain poorly understood from ecological, behavioral, and evolutionary standpoints. To begin to address this discrepancy, the researchers previously conducted detailed studies of the control and function of rapid color change in male veiled chameleons, Chamaeleo calyptratus. However, a broader context is required to understand the evolutionary origins of and constraints on these unusual color change signals. In this study, the researchers will conduct a comparative study of Bradypodion dwarf chameleons to investigate how and why color change signals evolved. Dwarf chameleons exhibit marked variation in color change and display behavior among species, making them ideal for testing evolutionary hypotheses about the origin and function of this rare signal type. This study seeks to determine whether color change evolved to accentuate behavioral displays (or vice versa), or arose as a signal independent of complex behaviors and evaluate potential phylogenetic constraints on color change. In addition to communicating findings in scientific journals, the researchers will partner with outreach programs at Arizona State University and the South African National Biodiversity Institute to share major research findings via customized learning activities for middle school students in Arizona and South Africa. To better understand whether elaborate behavioral displays evolved before, after, or concurrently with complex color change signals, the researchers will measure natural suites of intraspecific behavioral (i.e. aggressive/submissive) and color signals in 12 species of dwarf chameleons using high-definition video cameras to record staged, aggressive interactions between conspecifics in each species natural habitat. Still photos of the animals, concurrently with video, will be taken during aggressive trials and colorimetric data will be collected throughout behavioral displays and bouts of rapid color change. Felsenstein's independent contrasts and phylogenetic generalized least squares (PGLS) analysis will be used to evaluate the evolutionary relationships between multiple aspects of display colorimetrics and display behaviors, and the strength of the phylogenetic signal will be evaluated for all color and behavioral signals. Lastly, the program Mesquite will be used to reconstruct ancestral states of behavioral displays and color signals in an attempt to disentangle the order and patterns of signal elaboration.