Evolution of anoline lizard display behavior

Abstract

Based on my conceptual framework of anoline display behavior, I am suggesting the following evolutionary trends. Lateral presentation during display was probably promoted by monocular vision. Along with lateral presentation, postures evolved to increase lateral outline. These postures which magnified body size were probably of selective advantage within aggressive social contexts since larger animals tend to dominate smaller ones through bluff. Body movement evolved along with lateral orientation and size-enhancing postures. These movements would be most effective if they complemented lateral orientation. Effectors available for such movements were primarily pre-adapted for vertical motion. The patterns of movement generated were probably simple oscillatory bobbing movements by the head which were weakly stereotyped, interspecifically similar, appearing in many contexts, and having a weakly defined information content. Events having selective advantage for species recognition promoted stereotypy of bobbing behavior into species-unique displays; each species had its unique signature display which served in a manifold communicatory capacity. The signature display appeared in assertion, courtship, and challenge contexts. Its information content varied depending upon context and recipient of the display (e.g., male or female). Besides the stereotyped aspects of the display, certain features remained variable with potential information significance. Core variability (see text) promotes individual recognition and may be the origin of new unique display patterns as sibling species emerge. Display modifiers (see text) are variable display features shared by members of a population (many being shared interspecifically) that provide a graded appearance to display performance; modifiers can indicate level of arousal and facilitate interspecific communication. For some species display repertoire size seems to have evolved from a single display (signature display) to repertoires of multiple displays; these subsequent displays are generally restricted to aggressive interactions. © 1977 American Society of Zoologists.