Many animals undergo complete metamorphosis, where larval forms change abruptly in adulthood. Colour change during ontogeny is common, but there is little understanding of evolutionary patterns in these changes. Here we use data on larval and adult colour for 246 butterfly species (61% of all species in Australia) to test whether the evolution of colour is coupled between life stages. We show that adults are more variable in colour across species than caterpillars and that male adult colour has lower phylogenetic signal. These results suggest that sexual selection is driving colour diversity in male adult butterflies at a broad scale. Moreover, colour similarities between species at the larval stage do not predict colour similarities at the adult stage, indicating that colour evolution is decoupled between young and adult forms. Most species transition from cryptic coloration as caterpillars to conspicuous colouration as adults, but even species with conspicuous caterpillars change to different conspicuous colours as adults. The use of high-contrast coloration is correlated with body size in caterpillars but not adults. Taken together, our results suggest a change in the relative importance of different selective pressures at different life stages, resulting in the evolutionary decoupling of coloration through ontogeny. 

We collected standarised RGB values from online photographs for 246 species of Australian butterflies and their caterpillars. The sRGB values presented were converted from raw aRGB values and an equation in an R function, which can be sent on request.

butter2_extractecNov11.csv -- dataset with all colours measured, for use in R code

butter2_extractecNov11.xls -- dataset but with metadata as tab

Also included: phylogenies used, file names to match data with phylogeny, R code and R functions employed.

Column headings for dataset: