Male aggression varies with throat color in 2 distinct populations of the mesquite lizard

We describe discrete variation in throat color, an important sexual signal, in males of 2 populations of the mesquite lizard (Sceloporus grammicus). At one locality, males exhibit orange, yellow, and blue morphs; whereas at the other, males exhibit orange, yellow, and white morphs. We performed dyadic agonistic behavior trials in both populations and found that variation in throat color is associated with variation in aggression level. However, the association between color and behavior is not the same between these 2 populations. The association between color and behavior in the mesquite lizard is also not consistent with some of the associations documented in closely related species with variable throat color. Our findings suggest that although the tendency for discrete color variation to signal alternative reproductive tactics is phylogenetically widespread, both the color signals and the behaviors associated with them may change rapidly over evolutionary time.