Bee lab explores pollinator decline

By Susan E. Fahrbach, Chair, Department of Biology

The focus of the Bee Research Laboratory in the Department of Biology at Wake Forest University might surprise you. Our laboratory does not study pollination biology or the economic impact of honey bees on crop production. And although we maintain numerous hives and therefore can’t avoid producing wax and honey, we’d almost rather that we didn’t have to as these substances make the lab sticky. Our fascination with the honey bee instead grows out of our delight in the bee brain. The million nerve cells that make up a worker bee’s brain support a rich behavioral repertoire. Our goals are to understand how practicing a task (for example, collecting nectar from flowers) changes the structure of nerve cells, and how subsequent behavior is in turn changed as a result. Because the events we study occur at the cellular and molecular levels, our research provides insights into the workings of the nerve cells of all animals, including humans. We therefore use the honey bee as a model organism. It’s just right for this purpose because honey bee brains are significantly smaller than a mouse or a human brain and because honey bee behavior is easily studied under natural conditions. This means that we don’t have to resort to studying artificial, laboratory behaviors (think of a rat pressing a lever to get a food pellet or a fruit fly jumping to avoid an electric shock to its feet) to learn how the brain works.

It would, however, be disingenuous for us not to acknowledge that our brain research is only possible because of the long human tradition of keeping honey bees for pollination and honey and wax production. Humans have been keeping honey bees in hives for at least 3000 years and in the process have gained a treasure trove of knowledge of bee biology and behavior. For the most part, humans and bees seem to have had a harmonious relationship, and humans have deliberately introduced honey bees, which originally evolved in Africa (like humans!), to all parts of our planet with flowering plants. It is astonishing to think that this introduced, non-native species now contributes billions of dollars annually to the value of U.S. crops. It is therefore a matter of real economic concern that North American honey bee populations are declining. This decline, which has been widely reported in the popular media, has not impacted our lab’s ability to do our brain research, but it has inspired us to turn some of our research tools to the study of honey bee health. For example, in collaboration with researchers at the University of North Carolina-Greensboro, we recently investigated the impact of pesticide exposure on cell replacement in the honey bee gut. The results contained good news and bad news. We found that many commonly used insecticides did not have a negative impact on the bee gut. But we were surprised to learn that some of the drugs used by beekeepers to control bee infections and parasites alter the gut, which may in turn result in malnutrition. We are currently continuing our gut studies with undergraduate research teams funded by a grant from the National Science Foundation.

The decline in pollinators is not limited to honey bees. There is evidence of a general reduction in insect pollinators, including native pollinators such as bumblebees and solitary bees. Although the causes of the decline are hard to pin down, some pollinator losses have occurred in association with the use of new insecticides. The neonicotinoids are especially suspect because they are systemic insecticides, which means that once they are absorbed by a plant they are found in all plant tissues, including pollen and nectar. Some neonicotinoids remain in the soil across growing seasons. As a result, pollinators may be chronically exposed to low doses of these toxins. In collaboration with researchers from the University of Ghent in Belgium, we adapted one of the methods we use to study honey bee nerve cells to investigate the effects of the neonicotinoid insecticide imidacloprid on growth of bumblebee nerve cells in cell culture. The results were striking: moderate to high doses of this insecticide almost completely inhibited the growth of cultured nerve cells. Of course, growth in a culture dish and growth in an intact brain are two very different phenomena, but these results raise at least a small red flag. Our lab hopes to obtain funding to extend these studies to other insecticides and to other species.

If you are reading the CEES newsletter you are likely interested in the possible impacts of neonicotinoids on local pollinators. Unfortunately, at present it’s hard to say anything definitive given that we have almost no long-term information on local pollinator populations. In my own experience, I have noted that published research on neonicotinoids tends to focus on their agricultural use, but also that a gardener can walk into any lawn and garden center and purchase numerous products containing neonicotinoids – foliar sprays, granules, soil drenches – for application to ornamental flowers, fruits, vegetables, trees, and shrubs. Here I’d like to echo the advice of The Xerces Society for Invertebrate Conservation: Make your garden pollinator friendly by avoiding the use of neonicotinoids in your garden or yard. Specifically, don’t buy any products that contain imidacloprid, acetamiprid, dinotefuran, clothianidin, or thiamethoxam. Keep in mind that insecticides designated safe for humans and pets have the potential to harm pollinators.

In the Wake Forest bee lab we’d rather spend our precious research time in our ivory tower studying brains instead of pesticides, but pollinators in distress are simply too important to ignore.