2. Mr. Ibrahim Salman

Studies along geographical gradients can improve the understanding of the diverse selective forces that drive floral signals and insect distribution, and particularly of the way in which local habitat conditions affect floral signals within and among populations. Here, we provided an overview of variation in plant-pollinator interactions along a geographical gradient and related it to the strategy adopted by the plants in response to their habitat. We hypothesized that floral morphology and biochemistry were associated with biotic and abiotic environmental contexts. To test our hypothesis, we used six populations of white mustard (Sinapis alba, Brassicaceae) distributed from the Mediterranean to arid sites. To investigate if the S. alba populations are locally adapted to specific climatic conditions, and to detect possible environmental drivers of the adaptation, we performed a common garden experiment in the most arid site. We found that the more Mediterranean the populations, the larger their flowers, the higher their intracellular CO₂ concentration and the higher their leaf temperature values. In addition, we have found differences in the olfactory signal the population emitted: the more Mediterranean the population origin, the less maltose, and the more undecane the flower produced. The differences detected in the flower signals of the populations has affected the pollination services, causing the plant populations of more Mediterranean origin to be less attractive to the local, arid origin, pollinator community. Our results demonstrate the significance of local adaptation between plants and their pollinators for plant reproductive success.