Host finding and recognition by specialised bees

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Oligolectic bees collect pollen, on which they rear their offspring, from only a few related plant taxa. The cues these pollen specialist use to find and recognize their host plants are not well understood. The aim of this study is to evaluate in a comparative approach how different oligolectic bees, that are all specialized on Campanula pollen, find and recognise their host plants in comparison to a polylectic bee, and if different species of Campanula produce the same compounds that are used by oligoleges for flower recognition. Additionally, we will investigate, if the deceptive orchid Cephalanthera rubra, that is known to mimic visual cues of Campanula flowers, also mimics olfactory cues of Campanula flowers or pheromones of Chelostoma females in order to attract Chelostoma males for pollination. We will characterize the floral colour and scents of different Campanula species and of Ch. rubra, and determine their role in attracting the oligolectic/polylectic bees for pollination. We will perform electrophysiological analyses to identify possible behavioural-triggering compounds in complex odour blends of flowers and female Chelostoma bees. Electrophysiologically active compounds of flowers and bees will be identified by chemical analyses. Finally, the biological role of specific compounds for the oligolectic/polylectic bees will be tested in behavioural experiments, in large flight cages, where experimental conditions are very similar to that found in the field.