|Jürgens, A; Dötterl, S; Meve, U: The chemical nature of fetid floral odors in stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae), New Phytologist, 172, 452-468 (2006)|
Most stapeliad flowers emit an easily noticeable strong and fetid scent resembling that of carrion, urine or feces as an adaptation to flies as pollinators. Floral volatiles from 15 plant species (11 genera) were collected via headspace adsorption and thermal desorption and analyzed by GC-MS to get a better understanding of the odor chemistry of sapromyiophilous species in the Ceropegieae. Nitrogen containing compounds, fatty acid derivatives, benzenoids and polysulphides contribute most considerably to the fetid aroma. An analysis of the scent data using the chord-normalized expected species shared distances of the chemical profiles, followed by visualization of the data with nonmetric multidimensional scaling, showed that the species can be divided into four groups that seem to reflect different mimicry types: (1) species with p-cresol as a main compound but low amounts of polysulphides (herbivore feces mimicry), (2) species with a high content of polysulphides but low amounts of p-cresol (meat decomposition: carnivore/omnivore feces or carcass mimicry), (3) species with high relative amounts of heptanal and octanal (meat decomposition: carnivore/omnivore feces or carcass mimicry), and (4) species with hexanoic acid (urine mimicry).