Population differences in a lizard communicative display: evidence for rapid change in structure and function.

Population differences in a communicative display can lead to reproductive isolation and speciation, and are an indicator of the potential for rapid change in the display. Herein, we describe differences in the push-up displays produced by three populations of sagebrush lizards, Sceloporus graciosus, in the field. Lizards from these three populations differ in the use of display body postures, the number of legs extended to produce the up-and-down motion of the display, and the number of headbobs produced in each of three segments of the display. In addition, there is at least one behaviour that is unique to one of the three populations (the 'nodding run'). These differences among populations suggest that both the structure and the function of the push-up display are undergoing far more rapid change than was previously thought. Copyright 1998 The Association for the Study of Animal Behaviour.