貝食性オサムシの形態的多様化を促進させる決定要因

抄録

A stout-slender dimorphism is globally observed among carabid beetles feeding on land snails. In a representative snail-feeding carabid beetle Damaster blaptoides, I examined possible factors determining subsequent evolution toward stout or slender body shapes. I collected 1705 beetle specimens from 68 sampling points in the Japanese islands and analyzed them morphologically. The first and second principal components in a principal component analysis could be interpreted as body size and stout-slender body shape axes, respectively. I also examined the mean shell size of Euhadra, a genus of land snails frequently consumed by D. blaptoides, at each beetle sampling point, and examined the relation between the beetle body shape and snail body size. Populations of more slender beetles occurred in localities harboring larger snails, whereas stouter beetles inhabited localities harboring smaller snails, implying that local adaptation in response to snail size may have led to diversification of body shape in beetles. Beetle body size was also positively correlated with annual mean temperature, implying that climate conditions influence the evolution of beetle morphology. Populations of D. blaptoides showed distinctive isolation-by-distance patterns in population genetic structure, suggesting that geographic isolation might effectively enhance the local adaptation. Thus, food resources, climate, and geographic isolation may promote adaptive divergence of external morphology in snail-feeding carabid beetles.