Exploring Plant-Pollinator interactions: critical studies for the safeguard of wild Apoidea and spontaneous plant populations

The study of plant-pollinator relationship and the degree of their specialization is among the most lively and debated issues in plant biology and ecology. The fates of plants and bee pollinators are strictly connected: the severe decline lately encountered by wild Apoidea, which in turn results in a lower pollination rate, trigger the so-called “extinction vortex” phenomenon. This study was finalized to improve knowledge on plant-pollinator interactions, in ecological context with conservation needs. Field work on the natural populations of Dictamnus albus allowed us to define practical methods for the joint protection of wild Apoidea and endangered plants applicable in several contexts. In order to define the pollinator importance of single taxa and of the whole pollinator guild of D. albus, an index distinguishing between potential (PPI) and realized (RPI) pollinator importance was created. Moreover, it was assessed the effect of some abiotic and biotic factors on the abundance and activity pattern of flower-visiting insect groups. Laboratory experiments on Gentiana lutea nectar pointed out a gender-specific amino acid solution preference in Bombus terrestris, one of the main pollinator of this plant, and confirm a negative influence of high amino acid concentration diet on insect mortality. The behavioural study showed that β-alanine may affect either positively or negatively bumble bees walking and flying activities depending on its concentration, and that GABA enriched solution greatly increase bumble bee survival time. Studies on B. terrestris colony development and reproductive strategies led to define an inbreeding risk index (IRI) for the colony and highlighted the lack of an inbreeding-avoidance system in this species. Finally, three years of rearing practice allowed to provide new guidance methods for diapause and deposition in bumble bee artificial rearing. In conclusion, this thesis may help to better understand of the complex world of plant-pollinator relationships.