An experimental evaluation of traits that influence the sexual behaviour of pollinators in sexually deceptive orchids

Pollination by sexual deception of male insects is perhaps one of the most remarkable cases of mimicry in the plant kingdom. However, understanding the influence of floral traits on pollinator behaviour in sexually deceptive orchids is challenging, due to the risk of confounding changes in floral odour when manipulating morphology. Here, we investigated the floral traits influencing the sexual response of male Zaspilothynnus nigripes (Tiphiidae) wasps, a pollinator of two distantly related sexually deceptive orchids with contrasting floral architecture, Caladenia pectinata and Drakaea livida. In D. livida the chemical sexual attractant is emitted from the labellum, while in C. pectinata it is produced from the distal sepal tips, allowing manipulative experiments. When controlling for visual cues there was no difference in long distance attraction, though the floral odour of D. livida induced copulation more frequently than that of C. pectinata. The role of colour in pollinator sexual at...