ADAPTIVE PHENOTYPIC PLASTICITY AND ITS DIFFERENCE BETWEEN UNIVOLTINE AND MULTIVOLTINE POPULATIONS IN A BRUCHID BEETLE,KYTORHINUS SHARPIANUS

The multivoltine bruchid Kytorhinus sharpianus shows seasonal phenotypic plasticity in adult longevity, the preoviposition period, and the number of eggs laid without feeding between the diapausing and nondiapausing generations. This study compared the norms of reaction in three life-history traits between the univoltine Aomori and multivoltine Mitsuma populations. The directions of response in the norms of reaction were similar in both populations, although their response curves differed between populations. This result indicated a potential for variation in seasonal phenotypic plasticity in the univoltine population. However, the variation in the norms of reaction was small in both populations, suggesting strong selection pressure on the plasticity in the multivoltine population. These results also suggest that the univoltine Aomori population may have originated from a multivoltine population.