THE EFFECT OF VARIATION IN ENDOCRINE MECHANISMS ON NATURAL DISPLAY BEHAVIOR IN CARIBBEAN ANOLIS LIZARDS

Sexual display behaviors often consist of elaborate performances designed to attract potential mates, and increases in circulating androgens are frequently associated with increases in sexual display behavior. In Anolis lizard species, display behaviors consist of dewlap (i.e., throat fan) extensions and pushups, and species can vary dramatically in their patterns of display. My objective in this study was to determine whether interspecific differences in androgen receptors in the muscles controlling dewlap extension and pushup behaviors are associated with the frequency of use of those muscles during displays. I used behavioral data for adult males of five species of Anolis lizards from the Barahona region in southwestern Dominican Republic. I found that there is substantial variation across species in the number of pushups and dewlaps done in their displays. I also carried out controlled arena trials, where males of the same species were put together in a small cage to provoke displays at each other, and found display patterns consistent with their natural behavior. I determined the expression of androgen receptors in the muscles through immunocytochemistry, and found the expression of androgen receptor in dewlap-controlling muscles to be associated with dewlap display behavior. In addition, I determined the muscle fiber size and found bicep muscle fiber size to be associated with pushup display frequency. This study will contribute to our understanding of the morphological basis for behavior, particularly how endocrine mechanisms can lead to variation in social display behavior