Are tropical butterflies more colorful?
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There is a common and long-standing belief that tropical butterflies are more striking in their coloration than those of cooler climates. It has been suggested that this is due to more intense biotic selection or mate selection in the tropics. We tested whether there were differences in coloration by examining the dorsal surface color properties of male butterflies from three regions of the western hemisphere: the Jatun-Satcha Reserve in lowland Ecuador (tropical), the state of Florida, USA (subtropical) and the state of Maine, USA (cool temperate). We digitally photographed the dorsal wing and body surface of male butterfly specimens from Maine, Florida, and Ecuador. For each photograph, we analyzed the mean and variation for the color-parameters that are thought to be related to colorfulness; namely Hue, saturation and intensity. Overall, the Ecuadorian sample exhibited more varied intensity, saturation, and Hue compared to the other regions. These results suggest a more complex assemblage of colors and patterns regionally and on a butterfly-by-butterfly basis in the tropics. The greater complexity of colors within each butterfly in our Ecuadorian sample suggests that tropical butterflies are indeed more ‘colorful’, at least by some measures. Possible reasons for this include stronger predation pressure selecting for aposematism, greater species diversity selecting for camouflage or warning coloration against potential predators, and easier recognition of potential mates in a species rich environment.
KeywordsButterflies Coloration Tropical Temperate Latitude Aposematism
We thank the staff of the Lepidoptera collections of American Museum of Natural History, New York, and the Academy of Natural Sciences, Philadelphia, for their assistance in making it possible for us to photograph the specimens in their collections. In particular we wish to thank Dr. Jason Weintraub of the Academy of Natural Sciences for his very thorough advice. We thank Dr. Gareth Russell of Rutgers University with assistance in writing the MATLAB program used for color analysis.
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