Animals use certain traits or behaviors to signal to one another. Such signaling may be used to advertise specific qualities of the signaler and may impact the reproductive success of the individual. Though much research has focused on this relationship, the causal links between the signal and an animal's fitness (i.e., survival and reproduction) are unclear. This project will address this gap by studying a signal that advertises a functional trait. Functional traits are the combined output of different systems in an individual and can be the targets of selection. The goal of this research is to determine how signals and functional traits interact to determine fitness. Green anole lizards are well-suited to explore these relationships. The size of the extendable throat-fan, or dewlap, is related to the ability of a male to bite hard. Males that bite hard tend to win aggressive encounters with males that bite with less force. Experimental manipulations of dewlap size, combined with behavioral observations and genetic tests of reproductive success, will be used to determine how a signal and its correlated function influence male reproductive success. This area is relatively unexplored and has implications for theoretical work on animal signaling and sexual selection. Anole lizards are well-known by many and serve as model organisms for studies of behavior, ecology and evolution. Hence, they are ideal organisms to teach students of biology about animal communication and sexual selection. This study will involve undergraduates and outreach to the general public.
The research in this proposal investigated why animals have sexual signals. Many animals have sexual signals, which range in size from very modest ones to very large and elaboratge ones, such as found in peacocks. We examined the dewlap of anole lizards, which are colorful flaps of skin that are used by males and females to communicate with one another. We investigated whether making the dewlap smaller would reduce reproductive success of these lizards. We performed cage experiments where we had two kinds of males, both dewlap-reduced, and non-dewlap reduced, interact with females, and we attempted to assess whether this affected reproductive success. Also, we examined whether reducing the dewlap affected the ability of male anoles to fight one another. We found that it is not the size of the dewlap per se that is important but rather the ability of male lizards to bite, which is transmitted honestly by the size and shape of the dewlap. Overall, these results clearly show that seuxal signals play a vital role in the lives of these animals, becasue they reveal key fighting traits that project male quality. We believe that this work is of general importance because it reveals why animals behave and are formed in a particular way.
