Seasonal wing colour plasticity varies dramatically between buckeye butterfly populations in different climatic zones

1. In the present study, how seasonal wing colour plasticity in buckeye butterflies (Junonia coenia Hübner) differs between populations in different climatic regions, and whether these differences are explained by regional environmental differences or reflect genetic divergences in plasticity is addressed. 2. Using museum specimen data, it is shown that buckeye wing colour variation is much greater in populations from the humid and subtropical climates of the eastern U.S.A. than in populations from the desert and mediterranean climates of the western U.S.A. 3. Museum specimen data further show that wing colour in eastern populations is strongly correlated with seasonal variation in day length and temperature, whereas wing colour in western populations is only weakly associated with these cues. 4. Controlled incubator experiments comparing Southern California and North Carolina populations suggest that regional differences in wing pattern variation are attributable to dramatically increased robustness to environmental variation in western populations. 5. Together these experiments show that while phenotypic variation can be influenced by environmental cues, the range of this variation can genetically diverge between populations in different regions.