Scent biogenesis and deceptive strategies in Arum maculatum

Most plants are pollinated by animals that transfer the pollen among flowers. Thus, pollination is an important ecosystem service. For pollination to occur, the flowers must advertise their presence, for making it possible for their pollinators to localize them. Most important are floral volatiles and colours. While most plants reward their pollinators for the pollination service, often with nectar and pollen, 4-6% of the flowering plants trick their pollinators by chemically imitating a reward they do not provide. Floral volatiles are chemically diverse, with c. 2000 different compounds already described. Despite the recent advances in our understanding of the importance of floral scents in plant-pollinator communication, for most of the pollination systems we do not know the compounds responsible for pollinator attraction. Further, there are big gaps in our understanding of the biosynthesis and secretion of these compounds. One fascinating deceptive plant is the European cuckoopint Arum maculatum (Araceae), which has the most complex scent known so far (c. 300 compounds in total, up to 150 per individual), used the imitate egg-laying sites of its pollinators, especially sink flies. Cow dung and decaying organic matter are the substrates supposedly imitated by the inflorescence. Further, some of the floral volatiles released are chemically similar to psychodid male sex pheromones, making it possible that A. maculatum does not only imitate brood substrates but also sex pheromones of its pollinators. This plant is also well known for rising its floral temperature during pollinator attraction, likely to increase the amount of volatiles released into the air, and for temporary (c. 1 day) trapping its sink fly pollinators. To better understand how and why so many volatiles are produced and secreted by A. maculatum, we aim to study the physiological and genetic bases of the floral scent biosynthesis and secretion, identify the floral scent compounds responsible for pollinator attraction, and test whether some of those compounds are indeed sex pheromones of sink fly pollinators. To achieve these goals, we perform laboratory and field experiments, and use chemistry, chemical ecology, ethology, and genetics. The project will study for the first time whether a plant has a two deceptive pollination systems in one, by chemically imitating both egg-laying sites and mating partners (sex pheromones). We may evidence the first example of chemical sexual deception outside the orchids. The international research team consists of researchers from Austria (Paris Lodron University of Salzburg) and France (CNRS University of Corsica, Jean Monet University), with partners both in France and Germany (University of Tours and TU Braunschweig).