摘要Color polymorphism offers rich opportunities for studying the eco-evolutionary mechanisms that drive the adaptations of local populations to heterogeneous and changing environments.We explored the color morph diversity and composition in a Chrysomela lapponica leaf beetle across its entire distribution range to test the hy-pothesis that environmental and climatic variables shape spatiotemporal variation in the phenotypic structure of a polymorphic species.We obtained information on 13 617 spec-imens of this beetle from museums,private collections,and websites.These specimens(collected from 1830-2020)originated from 959 localities spanning 33° latitude,178° longitude,and 4200 m altitude.We classified the beetles into five color morphs and searched for environmental factors that could explain the variation in the level of poly-morphism(quantified by the Shannon diversity index)and in the relative frequencies of individual color morphs.The highest level of polymorphism was found at high lati-tudes and altitudes.The color morphs differed in their climatic requirements;composi-tion of colour morphs was independent of the geographic distance that separated popu-lations but changed with collection year,longitude,mean July temperature and between-year temperature fluctuations.The proportion of melanic beetles,in line with the ther-mal melanism hypothesis,increased with increasing latitude and altitude and decreased with increasing climate seasonality.Melanic morph frequencies also declined during the past century,but only at high latitudes and altitudes where recent climate warm-ing was especially strong.The observed patterns suggest that color polymorphism is especially advantageous for populations inhabiting unpredictable environments,presum-ably due to the different climatic requirements of coexisting color morphs.