Food-deceptive pollination of Vanda concolor (Orchidaceae)

Food-deceptive pollination is one of the significant pollination mechanisms among orchids. Given floral syndromes and low natural fruit setting rate of Vanda concolor, we assume that this orchid species is in compliance with a food-deceptive pollination mechanism. In order to test our assumption, we investigated pollination biology of V. concolor during 2012-2013 in the Yachang National Nature Reserve, which is located in northwestern Guangxi, China. Our observations confirmed that the flowers were self-compatible but required floral visitors. Both Xylocopa rufipes and Bombus kulingensis are effective pollinators with the former more effective than the latter. Foraging in the flowers mainly occurred in two periods: 68% in 10:00 am—12:30 pm and 16% in 13:30 pm—14:30 pm. Mahonia beaill, Stachyurus chinensis and Vanda concolor have the same flowering season in the study area, and the bright yellow color of Mahonia beaill flowers is similar to the color of spots on Vanda concolor flowers. Five chemical compounds have been identified as the volatile constituents of flower fragrance of the orchid, of which 1,6,10-dodecatrien-3-ol,3,7,11-trimethyl-,(E)-(29.6%) and cinnamaldehyde,(E)-(27.0%) are the most abundant compounds. We consider that the plant attracts pollinators into flowers for foraging by floral fragrance and yellow spots in flowers, and it follows the food-deceptive pollination mechanism.