Trends in seasonal polymorphism among Japanese butterfly species.

Abstract

Seasonal polymorphism in butterflies is widely known among lepidopterists but has not been studied comprehensively. In this study, we analyzed a complete list of Japanese butterflies to elucidate possible morphological features that exhibit seasonal polymorphism. We found that 150 of 250 species were multivoltine; of these, 113 species exhibited seasonal polymorphism in adult wing color, wing shape, or body size. Approximately 65% of seasonally polymorphic species had darker color on the dorsal side of wings in the high-temperature season, and nearly 40% of seasonally polymorphic species had lighter color on the ventral side of wings in the high-temperature season. Most species exhibited no morphological changes in wing shape, and more than 60% of seasonally polymorphic species showed a seasonal change in body size. The darkening of dorsal wing color in the high-temperature season was the most frequent phenotypic change among all Japanese butterfly species. Our results further indicated that seasonal polymorphism trends in Japanese butterflies varied among butterfly families.