Benjamin Kaluza, Helen Wallace, Tim Heard& Sara Leonhardt.
Bee pollinators are threatened by anthropogenic activities, and habitat loss and –conversion are key causes for currently observed widespread declines in wild bees. Moreover, decreasing abundance and diversity of foraging plants directly limits bee foraging for plant resources (pollen, nectar and resin). Yet how plant richness and plant resource abundance influence foraging patterns and ultimately bee colony performance is still little understood.

In a long term experiment, we placed hives of an Australian eusocial stingless bee, Tetragonula carbonaria, in their natural habitat (subtropical forests) and two landscapes differently altered by humans (suburban gardens and macadamia plantations). To better understand how resource availability and diversity in interaction with nutrient quality affect bees, we monitored foraging patterns and colony growth across seasons over three years.

We found that bees collect higher diversity and greater quantities of resources and had greater reproduction in gardens compared to forests and plantations. Nutritional quality of honey and antimicrobial activity of resin storages was similar across landscapes, but mostly depended on plant species composition. Pollen protein content however was high in plantations and gardens, not in forests. Our results thus demonstrate that high resource abundance, diversity and quality are not necessarily associated with large proportions of natural habitats within the bees’ foraging range, but depend on overall plant species richness and composition and thus year-long resource availability, which ultimately drive reproduction rates in social bees.