Pollination of <i>Dendrobium infundibulum, Cymbidium insigne</i> (Orchidaceae) and <i>Rhododendron lyi</i> (Ericaceae) by <i>Bombus eximius</i> (Apidae) in Thailand: a possible case of floral mimicry

Abstract

ABSTRACT The orchids Dendrobium infundibulum and Cymbidium insigne are pollinated by the bumblebee Bombus eximius , which also pollinates the ericaceous shrub Rhododendron lyi , A study of the three plants and the bumblebee in maquis-like mountainous vegetation in northern Thailand suggests that they form a floral mimicry system with two mimics (the orchids) to one model ( R. lyi ). The flowers of the two orchid species offer no food reward to pollinators. Flowers of the three species show definite morphological and visual resemblance, and the species overlap to a great extent in flowering phenology and habitat Mimic flowers were much less numerous than model flowers, which occurred abundantly in the area. The rate of pollinaria removal was very low in both orchid species, resulting in a relatively small percentage of fruit set, especially in D. infundibulum . Infrequency of pollinator visits was, however, somewhat counterbalanced by long-lasting flowers. The pollinaria of the two orchid species are differently positioned on the bee, hence interference between the different reproductive systems is minimized. This is the first report which indicates floral mimicry from tropical Asia.