Lay summary
Plants often need pollinators to transfer their gametes during sexual reproduction. Because pollinators have specific preferences for signals (color, scent) and morphology, they select for certain floral traits. Such pollinator-mediated selection can be measured through connecting reproductive success (e.g. fruit set) with the floral characters a plant produces. Since pollinator faunas vary on a geographical scale, e.g. due to climatic factors in different altitudinal ranges, regional differences in selection for floral traits is expected, leading to the adaptation of plants to a landscape "pollinator mosaic". Adaptation to regional differences in pollinators can result in isolation, and the formation of different species as a consequence. The here proposed research strives to examine different mechanism of pollinator-mediated evolution in plants. The proposed experiments will be done comparatively in two different pollination systems, namely food reward and sexual deception within the subtribe Orchidinae (Orchidaceae). Sexual deception involves the imitation of mating signals by flowers and pollination by sexually aroused male pollinators. The comparative approach is chosen to acknowledge the likely differences of evolutionary mechanisms among plants with different pollination systems. To test for local adaptation, plants will be transferred among populations and reproductive success compared to local control plants. Floral traits (morphology, color, scent) will be measured in the study populations. Selection on floral traits will be examined in local and transferred plants. Additionally, odor genes will be sequenced and patterns of variability compared with neutral markers, within and among populations. Selection dynamics in relation to population densities will be examined in plot experiments by manipulating population densities and monitoring reproductive success. The here proposed research is a comprehensive and novel approach to pollinator-driven evolution in plants. The multi-population setting will shed light on the microevolutionary processes, i.e. local adaptation and selection dynamics that underlie the astonishing floral diversity found within and among plant species. Environmental change is expected to impact on plants and their biotic interactions, through change in pollinator faunas and thus selective environment for reproductive traits. The combination of lowland (warm) and alpine (cold) habitats in this study will add insights into how climatic changes can impact on plant pollinator interactions. The assessment of variability in adaptive genes will provide insight into the adaptability of populations for the respective traits