Frequency-dependent predation (FDP), or apostatic selection, is often assumed to be a main evolutionary process to maintain color-pattern polymorphism, particularly when colors are drab. Under this hypothesis, differences in survival rate based on color pattern should be detectable. In many species of anoles, females show variation in dorsal patterns. These patterns consist of drab colors and are thought to have evolved as a predator-avoidance mechanism. We tested the FDP hypothesis for Norops humilis at the La Selva Biological Station in Costa Rica. Three female patterns are found in this population. The dotted pattern occurs in males as well as females, whereas vertebral stripe and reticulated morphs are only found in females. To test FDP, we compared morph frequencies from population data collected at several sampling periods between 1981 and 2007, expecting to see fluctuations in frequencies over time. In addition, we predicted that the most common morph would experience higher mortality. Therefore, we analyzed survival rates from a capture–recapture study. We found that the dotted morph was more common in juveniles as well as in adults and adult morph frequencies remained stable over time. Survival rates supported this, showing no significant difference among morphs. The evidence supported rejection of the FDP hypothesis in this population of lizards. Possible scenarios to explain the stability of dorsal patterns and suggestions for future research are presented.
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Vol. 67 • No. 4