Temporal Variation in Sexual Size Dimorphism of Anolis limifrons in Panama

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Abstract
Null growth-based models were used to examine variation in sexual size dimorphism (SSD) in a population of the lizard Anolis limifrons in Panama. 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. Despite this, the population exhibited significant seasonal variation in SSD such that adult males were significantly larger than expected during the late wet season and early dry season. During this period, juveniles enter the adult population through growth. We suggest that skews in size distributions of adult males during the late wet season and early dry season result from sampling bias caused by aggression of old (and large) adult males toward young (and small) adult males. As a consequence of this aggression by established adult males, young adult males 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 way that null growth-based models can be used to uncover interesting patterns and generate novel hypotheses about proximate factors that affect observed size distributions of adult females and males.

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