The effects of temperature, urbanisation, and artificial light on phototaxis in eusocial and non-eusocial bees

Climate change and urbanisation are major drivers of global insect pollinator decline. However, the combined effects of these stressors remain poorly understood, particularly in relation to pollinator behaviour. Understanding how these threats alter key foraging behaviours is critical for developing effective conservation and management strategies. Our study explores how temperature and urbanisation impact positive phototaxis (attraction and movement towards light) in native Australian non-eusocial bees, predominantly Lasioglossum, and the eusocial introduced European honeybee (Apis mellifera). The study was conducted in a large, urbanised city, characterised by a growing population and urban sprawl. Using bees collected from urban and natural sites across Greater Melbourne in Australia, we measured phototactic responses under varying temperatures (28 °C and 32 °C) towards narrowband ultraviolet (UV) light (simulating more ecologically relevant light) and artificial white light (simulating less ecologically relevant light). Our results revealed significant differences in phototactic behaviour between native bees and honeybees, with honeybees exhibiting faster responses under all conditions. Temperature significantly impacted phototaxis for honeybees, with the higher temperature resulting in slower phototaxis, but no significant effect was observed for native bees. We found that neither urbanisation nor light type had a significant effect on response time in either honeybee or native bees. This study contributes to our growing understanding of how anthropogenic disturbance may alter critical pollinator behaviours, which in turn, may impact ecosystem function as bees are keystone species in many environments.