Aspect diversity in moths revisited.

Ricklefs and O'Rourke compared the diversity of appearance (aspect diversity) in samples of moths attracted to ultraviolet lights in Colorado, Arizona, and Panama. The more species-rich Panamanian assemblage of moths exhibited proportionately greater diversity of color and form, which supported stronger frequency-dependent selection by predators to diversify the strategies that moths adopt to achieve crypsis in an ecological space composed of resting backgrounds. Comparable analyses of 15 additional samples obtained from Ecuador to Canada fail to support Ricklefs and O'Rourke's original result. In the present analysis, two measures of the volume of aspect space were unrelated to the number of species per sample and did not differ between temperate and tropical localities. Either frequency-dependent (apostatic) selection is not a powerful force in diversifying moth appearance, or it does not vary with latitude, or potential resting backgrounds and cryptic strategies are similarly constrained in temperate and tropical regions.