Hairy, hairy quite contrary: Pollination and functional floral traits in a hirsute carrion‐scented stapeliad

Floral mimicry of decaying substrates of animal origin, such as carrion or faeces, is associated with unusual traits such as geoflory, deep maroon or yellow colouration, floral hairs and unpleasant odour, but the functional significance of these traits for attracting and manipulating pollinators has seldom been examined. We investigated the pollination system of Ceropegia pulvinata var. pulvinata , a stapeliad with very hairy geoflorous flowers, extremely variable floral colours and a carrion‐like odour. We used manipulative experiments to test the functional significance of some of these traits. We confirmed that the flowers attracted saprophilous male and female flies from three families (Calliphoridae, Muscidae, Sarcophagidae), although only Lucilia calliphorids and some sarcophagids carried pollinaria. Visiting flies flew or walked onto flowers and typically spent more than 2 minutes walking haphazardly around probing the corolla, with 65%–74% of flies going on to probe the gynostegium (required to effect pollination). There was no difference between visitors or their behaviour on yellow versus maroon flowers. Analysis of floral scent using gas chromatography‐mass spectrometry confirmed that the odour is dominated by dimethyl di‐ and trisulfide, but also contains large relative amounts of p ‐cresol, indole and limonene, with minor differences between yellow and maroon flowers. Reflectance spectra of flowers were characterised by low chroma (i.e., low spectral purity), with some chromatic contrast between different floral parts and UV reflectance from the style head and hairs on the corolla margin for both yellow and maroon flowers. Flowers that were concealed from view still attracted flies, but significantly fewer than were attracted by visible flowers. Experimental removal of hairs from the surface of the corolla did not affect the arrival rates of flies in comparison to control flowers, but reduced the amount of time flies spent probing the flower. Fly arrival rates were reduced when flowers were raised 1 m above the ground, but not when they were raised by 0.5 m. Our results confirm that these flowers deploy both odour and visual signals to attract their saprophilous fly pollinators, and that geoflory and floral hairs also influence the attraction or behaviour of flies in ways that may enhance the success of pollination.