Format: ORAL

Noa L. A. Schwabe1, Bentje Bossert2, Ingo Grass2, Philipp M. Schlter1

1 Department of Plant Evolutionary Biology, Institute of Biology, University of Hohenheim, Stuttgart, Germany 2 Department of Ecology of Tropical Agricultural Systems, Institute of Agricultural Sciences in the Tropics, University of Hohenheim, Stuttgart, Germany

In food-deceptive pollination systems, plants attract pollinators without offering any reward. The plant lures the insect into pollination by showing traits similar to rewarding flowers. Our research aims to comprehensively understand the pollination ecology within a food-deceptive system (Orchis militaris) and to identify key traits influencing pollinator attraction, spatial heterogeneity, pollination success, and consequently, plant fitness. Furthermore, we are investigating the avoidance behavior of pollinators in this deceptive system. We are studying two distinct populations, both located north of the Alps, approximately 650 km apart, covering the broad habitat requirements of O. militaris. By identifying effective pollinators of O. militaris, along with their co-vegetation, our preliminary results indicate marked differences between the two populations, highlighting a broad pollinator spectrum. The overall pollination success and seed set was high. Main pollinators are Hymenoptera (Apidae), ranging from large (Apis mellifera) to small (Lasioglossum marginatum). While pollinator abundance appears to be directly linked to plant fitness, current observations indicate that the density of deceptive orchids does not adversely affect pollination success. Notably, we observed that bees seemingly do not exhibit avoidance behavior even in high-density deceptive orchid populations. These preliminary results contradict the hypothesis that pollinators learn deceptive strategies, and therefore show avoidance behavior. As a next step, we aim to understand the mechanisms underlying this observation. To examine the learning process of pollinators, specifically whether they avoid specific floral traits (color) or areas after encountering non-rewarding plants, we are planning to mark bees in the field and to conduct choice experiments with A. mellifera. In summary, our study provides insights into pollination ecology and the associated pollinator behavior contributing to the evolution of deceptive systems, which is also of relevance for habitat conservation and management strategies in times of rapid biodiversity declines.