Climate change impact on crop plant-pollinator communication

Environmental conditions are changing and the global mean surface temperature is projected to increase up to 5C during the 21th century. Climate change is expected to undermine food security, since both crops and pollinators may be negatively affected. Floral scent is an important communication channel between plants and their pollinators, and changes in temperature impact flower scent emissions. However, the effects these changes in floral scent have on plant-pollinator interactions are still unknown. Our proposal will test for the first time whether shifts in floral emissions due to a temperature increase predicted by climate change scenarios affect the chemical communication between plants and their pollinators. Therefore, the objectives of this proposal are i) to analyze the flower scent of important crop plants at optimal growing temperatures and temperatures 5 C higher; ii) to test whether different bee pollinators detect and behaviorally respond to potential changes in scent bouquet induced by an increase in temperature. We hypothesize that increased temperatures will induce an increase in the amount of scent and changes in relative composition of floral VOCs in the target crop species. These expected differences in scent patterns may have negative, neutral or positive effects on pollinator attraction. We selected buckwheat (Fagopyrum esculentum - Polygonaceae), oilseed rape (Brassica napus - Brasicaceae), and strawberry (Fragaria ananassa - Rosaceae) for our study as models, all of which worldwide crops used as human food and dependent on animal pollination. We will cultivate the crop plants in plant-growth chambers at two different temperatures. At these conditions, floral scents will be sampled by dynamic headspace and analyzed by gas chromatography coupled to mass spectrometry (GC/MS) to verify, if temperature increase by 5C induces quantitative and qualitative changes in floral emissions. In parallel, we will perform electrophysiological tests by gas chromatography coupled to electroantennographic detection (GC/EAD) and behavioral assays in a flight-cage to test responses of pollinators to likely changed floral scent bouquets. This study will provide findings of climate change effects on communication between crop plants and pollinators which need urgently be studied, since negative effects would have serious consequences on agriculture and production of human food. This proposal comprises international mobility of the applicant, Dr. Cordeiro, from Brazil to the group of Univ.-Prof. Dr Dötterl at the University of Salzburg- Austria. Dr. Cordeiro is a young researcher with excellent scientific papers. His expertise, which will be transferred to the host organization, nicely fits the requirements of this proposal. Through advanced training in chemical ecology he will expand his knowledge in this field of research. The approval of this proposal will be beneficial for creating long term collaborations between Austria and Brazil.

Global warming is expected to impact the communication between flowering plants and their pollinators. The aims of our project were to quantify the effects of increased air temperatures on floral scent emissions of three insect-pollinated crop plants (buckwheat, Fagopyrum esculentum - Polygonaceae; oilseed rape, Brassica napus - Brassicaceae; strawberry, Fragaria x ananassa - Rosaceae), and to test whether temperature-induced shifts in floral scent affect chemical communication with its main bee pollinators (Apis mellifera, Bombus terrestris, Osmia bicornis). The scent analyses showed that buckwheat and strawberry were affected by increased temperatures, whereas oilseed rape was not. Independent of temperature, scent of oilseed rape was dominated by p-anisaldehyde and linalool, with no difference also in the total amount of scent. Buckwheat emitted 2.4 ng of scent per flower and hour at optimal temperatures, dominated by 2- and 3-methylbutanoic acid (together 46%) and linalool (10%), and at warmer temperatures threefold less scent (0.7 ng/flower/hour), with the contribution of 2- and 3-methylbutanoic acid (73%) to the total scent being increased and linalool absent. However, in behavioral experiments, all three bee species did not discriminate between the scents of the two temperature scenarios. The crop species most affected by increased temperatures was strawberry. While strawberry flowers in the optimum scenario released 10.4 ng/flower/hour, mainly p-anisaldehyde (81%) and seven other scent compounds, in the warmer scenario, the flowers did not emit any detectable scent. In the behavioral experiments, the pollinators were attracted by the scents of the optimum scenario. Therefore, in this crop, the chemical communication between the flowers and their pollinators will be impaired by temperatures predicted by a global warming scenario. Overall, our results highlight that increased temperatures differently affect floral scent emissions and the olfactory communication between crop plants and their pollinators. This raises important ecological and agricultural questions, as decreased attractiveness of at least some of plant species to pollinators might result in insufficient pollination in these species with negative consequences for ecosystem functioning and crop yields.