Ecological and genetic differentiation among parapatric populations of bumblebee-pollinated plants.

四国香茶菜花冠筒长度具有地理变异性，与两种熊蜂传粉昆虫的喙长相对应。我们假设传粉者组合的海拔变化是介导I. shikokianus种群 花冠筒长度的差异可以用海拔高度差异来解释。然而，两种熊蜂的访问频率不同年份和授粉效果不依赖于花冠的长度和熊蜂的口器之间的对应关系。两种熊蜂的遗传距离主要由海拔分化和相对频率决定。这些结果表明，I. Shikokianus在不同海拔范围内均有分布，花冠筒长度的海拔梯度是长、短花冠种群间次生接触的结果。

The corolla tube length of Isodon shikokianus shows geographical variation, corresponding with the proboscis length of two bumblebee pollinator species. We hypothesized that altitudinal variation in the pollinator assemblage is a principal factor mediating morphological and genetic differentiation among I. shikokianus populations. The differentiation in corolla tube length was explained by altitudinal difference. However, visitation frequency of two bumblebee species vary among years and pollination effectiveness do not depend on correspondence between the lengths of the flower corolla and the mouthparts of the bumblebees. Genetic distance was explained by altitudinal differentiation and relative frequency of two bumblebee species. These results suggest that floral and genetic divergence of I. shikokianus occurred in different altitude range, and the altitudinal cline of corolla tube length was a result of secondary contact between the long and short corolla populations.