Impact of urbanization on wild bees underestimated

Date:  March 6, 2019

Source:  University of Michigan

Wild bees are indispensable pollinators, supporting both agricultural productivity and the diversity of flowering plants worldwide.

But wild bees are experiencing widespread declines resulting from multiple interacting factors. A new University of Michigan-led study suggests that the effects of one of those factors -- urbanization -- may have been underestimated.

The study, led by a group of current and former U-M students and conducted at sites across southeast Michigan, looks at one aspect of this topic they say has received scant attention from bee researchers: the sex ratio of wild bees and how it changes across a rural-to-urban land-use gradient.

The team found that the sex ratio of wild bees became more male-dominated as urbanization increased, mainly driven by a decline in medium- and large-bodied ground-nesting female bees. The study, published March 6 in the journal Scientific Reports, is believed to be the first investigation of observed sex ratio in a complete wild bee community along a rural-to-urban gradient.

"These findings have potential implications on bee population health and pollination services, since male and female bees often have different pollination behaviors," said Paul Glaum, one of the study's first authors and a postdoctoral researcher in U-M's Department of Ecology and Evolutionary Biology.

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