Three pollination morphs in Cimicifuga simplex; incipient speciation due to inferiority in competition.

Abstract

Cimicifuga simplex, a Japanese herb, has three different pollinator guilds. At high altitudes it is pollinated by bumblebees. In lowlands, Impatiens textori, a much superior nectar-producer, outcompetes it for bumblebees. In sunny lowland habitats, flowers of a second morph produce a two-component fragrance which facilitates pollination by fritillaries. In experiments, the two components separately had limited effect on alighting rate, while application of both together elevated the attractiveness of non-fragrant flowers to the same as for naturally fragrant flowers. In heavily shaded lowland habitats, a third morph with nonfragrant flowers does not blom until after I. textori, and is pollinated by occasional bumblebees. The data strongly suggest that inferiority in competition has induced incipient speciation in this plant species.