Observations on the pollination and breeding systems of two Corybas species (Diurideae; Orchidaceae) by fungus gnats (Mycetophilidae) in southwestern Yunnan, China

Abstract

AbstractModes of floral presentation in some angiosperms attract flies that eat and/or oviposit on seasonal fruiting bodies of fungi. Mushroom mimesis by orchid flowers has been speculated in the geoflorous, Indo-Malaysian-Australasian, genusCorybass.l. for decades but most studies remain fragmentary and are often inconclusive. Here we report the roles of fungus gnats as pollinators ofCorybas geminigibbusandC. shanlinshiensisin southwestern Yunnan, China, combining results of field observations, lab analyses, and manipulative experiments. Hand pollination experiments suggested both species were self-compatible but incapable of mechanical self-pollination, thereby requiring pollinators for fruit production. A female of aPhthiniasp. (Mycetophilidae) carried a pollinarium ofC. geminigibbusdorsally on its thorax. Two females and one male ofExechiasp. (Mycetophilidae) visiting flowers ofC. shanlinshiensiscarried dorsal depositions of pollinaria on their thoraces. Mycetophilid eggs were not found in the flowers of either species. The comparative fragrance analyses of these flowers and three co-fruiting mushroom species did not suggest that either orchid species was a brood-site mimic. This is the first confirmation of the dispersal of pollinaria ofCorybasspecies by fungus gnats in subtropical-temperate Asia.