Why plant diversity is so important for bee diversity

During summers, bumblebees and honey bees can be seen foraging on the same flower species, whether in Britain or many other countries. Now, researchers at the Laboratory of Apiculture and Social Insects (LASI) at the University of Sussex, have found that different bees dominate particular flower species and revealed why.

By studying 22 flower species in southern England and analysing the behaviour of more than 1000 bees, they found that ‘energy efficiency’ is a key factor when it comes to mediating competition.

Bee bodyweight and the rate at which a bee visits flowers determine how energy efficient they are. Bodyweight determines the energy used while flying and walking between flowers, with a bee that is twice as heavy using twice as much energy.

The rate at which a bee visits flowers, the number of flowers per minute, determines how much nectar, and therefore energy, it collects. Together, the ratio of these factors determines bee foraging energy efficiency.

Professor of Apiculture, Francis Ratnieks, said: “While they forage on the same flowers, frequently we find that bumblebees will outnumber honey bees on a particular flower species, while the reverse will be true on a different species growing nearby.”

“What was remarkable was that differences in foraging energy efficiency explained almost fully why bumblebees predominated on some flower species and honey bees on others.

“In essence, bumblebees have an advantage over honey bees in being faster at visiting flowers, so can gather more nectar (energy), but a disadvantage in being larger, and so using more of the nectar energy to power their foraging. On some flower species, this gave an overall advantage to bumblebees, but on others to honey bees”.