TEMPORAL VARIATION IN SEXUAL SIZE DIMORPHISM OF ANOLIS-LIMIFRONS IN PANAMA

Null growth-based models were used to examine variation in sexual size dimorphism (SSD) in a population of the lizard Anolis limifrons in Pa nama. Females and males have comparable asymptotic body sizes, growth trajectories, size at maturity, and adult survival rates. The species is, thus, an unlikely candidate for a comparative analysis of SSD. Des pite this, the population exhibited significant seasonal variation in SSD such that adult males were significantly larger than expected duri ng the late wet season and early dry season. During this period, juven iles enter the adult population through growth. We suggest that skews in size distributions of adult males during the late wet season and ea rly dry season result from sampling bias caused by aggression of old ( and large) adult males toward young (and small) adult males. As a cons equence of this aggression by established adult males, young adult mal es may be excluded from the microhabitats used by old adult males (and females), or they remain in that microhabitat but become behaviorally inconspicuous. In either case, the skewed size distributions are the result of sampling bias. This study provides an illustration of the wa y that null growth-based models can be used to uncover interesting pat terns and generate novel hypotheses about proximate factors that affec t observed size distributions of adult females and males.