Résumé
Objective Flowers in the genus Ceropegia L. (Apocynaceae) do not reward pollinators: pollination is based on deceit. Inside the flower, pollen grains are grouped within five pollinia, limiting transfer opportunities. In case of syntopy with species sharing the same pollination syndrome, the risk of losing its pollinia inside another species should induce a selection pressure on pollinator specificity. Method We collected data on basic pollination aspects of four Ceropegia species occurring syntopically in Thailand, analysed floral scent by gas chromatography linked to mass spectrometry (GC/MS), and determined compounds responsible for pollinator attraction in bioassays. Results All pollinators found in the flowers were Diptera from Milichiidae and Chloropidae families, known as kleptoparasites. The floral scents and the scent of a true bug found on site-supposed to be the model mimicked by the flowers-belonged to the same family. This suggests a kleptomyiophilous syndrome: the flower attracts Diptera feeding on the hemolymph of insects captured by arthropod predators. The four plant species showed clearly distinct pollinator communities and floral scents, yet the pollinator attraction with synthetic odors was less specific. Conclusion The pollinator specificity in a syntopic context was confirmed, and implied, at least in part, the floral scents.