How do Human-Induced Environmental Changes and Parasitism Influence Plant Traits Governing Bumblebee Foraging?

Abstract

This thesis examines how environmental changes shape interactions foraging behaviour of bumblebees (Bombus), important ecologically and economically pollinators. A literature review identified floral nutritional and morphological traits as being key for bumblebee attraction. Herbivory generally reduced attractiveness to bumblebees through their effects on these traits, while other environmental factors such as soil moisture or fertilizer use had context-dependent impacts. In an experimental study, I then tested how diet quality and infection with the parasite Crithidia bombi interactively influenced foraging behaviour and sensitivity to herbivore damage. Contrary to predictions, herbivory positively influenced bumblebee visitation, while having no effect on measured floral traits. Infection did not influence foraging decisions, but reduced overall foraging activity in a dose-dependent manner, while diet shaped visitation patterns without having an impact on infection intensity. Colony identity, plant height and floral display size were also key predictors of foraging behaviour. These findings highlight the hierarchical nature of interacting biotic and environmental factors in shaping pollinator foraging ecology.