Does Bee Diversity Change How Pollinators Behave in Blueberries?

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Bees are essential for blueberry pollination in addition to many other crops, and since 2009, we have conducted research to understand who the important pollinators are in North Carolina blueberries. This was the focus of recent masters student Shelley Roger’s thesis, which addressed three key questions: What bees are present in NC blueberries? How do those bee species perform as pollinators? And how do species interactions influence pollinator performance?

In the next few posts, we’ll highlight some of the useful results from this work. First we’ll address the question: Do bees behave differently when interacting with other species in blueberries?

Work conducted on sunflowers grown in California demonstrated that interactions with wild bees facilited greater pollination by honey bees through greater movement between flowers.

We suspected that a diverse pollinator community was also beneficial for blueberries, and we wanted to determine if similar mechanisms contributed to these benefits.

Bee interactions in blueberry fields are, however, rare. In 10 hours of video recordings we made in NC blueberry fields, only one interaction between bees (two honey bees) was observed.

A rare event, a southeastern blueberry bee approaches a honey bee foraging at a blueberry flower. Photo: Hannah Burrack

A rare event, a southeastern blueberry bee approaches a honey bee foraging at a blueberry flower. Photo: Hannah Burrack

In order to measure bee interactions, screen houses were stocked with honey bees and commercially available bumble bees  (Bombus impatiens) and provisioned with artificial feeders. Honey bees did not act differently when encountering other honey bees or bumble bees on the artifical feeders. They were more likely to leave the “flowers” when interacting with either than if left uninterupted. Interestingly, however, bumble bees were more likely to leave an artificial feeder when interacting with a honey bee than following an interaction with another bumble bee.

The infrequency of bee interactions in blueberries may suggest that species interactions may not be a main driver of the benefits of diversity in blueberries. Observations in our artifical arenas suggest that bee interactions on smaller flower clusters, such as blueberries, may differ from those seen in sunflowers.

Next, we’ll look at differences in pollinator performance in blueberries.

More information

Greenleaf, S.S. and C. Kremen. 2006. Wild bees enhance honey bees’ pollination of hybrid sunflower. PNAS.

Rogers, S.R., P. Cajarmarca, D.R. Tarpy, and H.J. Burrack 2013. Honey bees and bumble bees respond differently to inter- and intra-specific encounters. Apidologie.