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Why plant diversity is so important for bee diversity - University of Sussex

A bumble bee foraging on lavender. Photo taken by Prof Francis Ratnieks
A bumble bee foraging on lavender. Photo taken by Prof Francis Ratnieks

As abundant and widespread bees, it is common to see both bumble bees and honey bees foraging on the same flower species during the summer, whether in Britain or many other countries.

Yet researchers at the Laboratory of Apiculture and Social Insects (LASI) at the University of Sussex, show that these two different bees dominate on different flower species and have found out 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 when foraging. 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 bumble bees will outnumber honey bees on a particular flower species, while the reverse will be true on other species growing nearby. What was remarkable was that differences in foraging energy efficiency explained almost fully why bumble bees predominated on some flower species and honey bees on others. In essence, bumble bees 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 bumble bees, but on others to honey bees.”

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