Titre de la dissertation: « Pollinators diversity in Moroccan agroecosystems and the potential effect of climate change on crop pollinators ».

Promoteurs de thèse: Monsieur Denis Michez et Pierre Rasmont

Résumé de la dissertation: Pollinators, and the pollination services they provide, are essential for the reproduction of the majority of flowering plant, but also for a wide variety of crops. The aim of this thesis was to explore pollinators diversity in different agroecosystems and different ecoclimatic regions in Morocco and evaluate the potential effect of climate change on bee distribution. In the first chapter of the Ph-D, I described the diversity, abundance and community composition of pollinator insects visiting 22 crops in Morocco in four regions. I found that wild bees were the most abundant group in agroecosystems and contributed significantly to crops visitation. Three genera (Andrena, Lasioglossum and Xylocopa) were found to represent 53% of the total abundance of wild bees visiting crops. 213 bee species were identified as crop visitors (22% of national wild bee species richness). Comparison of the abundance, species richness, and community composition of wild bees visiting the same crops showed significant inter-regional differences for zucchini, faba bean, and eggplant. In the second chapter, I characterized wild bee-ensuring crop pollination service by selecting the abundant bee species visiting nine crops among four regions. 26 species of a total of 156 species visiting crops were found to be abundant. This represents only 7% of the total richness found in all agroecosystems and 2% of national richness. All of these bees are found as ground-nesting bee, with a long flight season. This finding was in accordance with many others researches in Northern countries (Europe and USA). In the last chapter, I investigated using species distribution modelling (i.e. SDMs) the potential effect of climate change and landscape composition on crop pollinator, focusing again on the abundant bee species visiting crops. This modeling approach showed that the distribution of crops pollinator in Morocco depend mainly on climatic variables (mostly the Aridity Index, Precipitation of Driest Month, and Thermicity Index) while four species are related to land cover variables (Herbaceous vegetation for open forest and closed forest). I found slight future reduction in a climatically suitable area for only three species (maximum 33%), Andrena propinqua, Lasioglossum lucidulum and Lasioglossum villosulum; while we found an increase in suitable areas for other species which could be of 71% of area gain. Regionally, we found that future climatic conditions might alter the spatial patterns of bee species in the driest region in southern Morocco (Draa-Tafilalet and Souss-Massa regions).