Research

blueberries

Blueberries are one of the many crops that require bees for their production.

Think for a moment of the foods you eat during the course of your day.  For those of us fortunate enough to have access to the bountiful varieties found at a local grocer , it’s an incredibly diverse selection of delicious & nutritious foods including grains, fruits, vegetables, nuts, and much more.  How is that food produced?  Where does it come from?  What are the challenges in growing it?  As it turns out, a large portion of food, just about 30%, is available to us thanks to some kind of insect.  An insect? Aren’t those just annoying critters that scurry about and gross me out?  Certainly not!

Insects are essential to helping to produce many of the foods we eat.  These pollinating insects, especially bees, help plants to reproduce and create the colorful fruits, vegetables, nuts, and seeds we love.   Despite their importance, a number of important bee species are in decline.  Increased intensity of farming, newly emerging diseases and parasites, increased use of pesticides, and climate change are all struggles bees face in many regions, especially in the US.  The familiar and fuzzy bumble bees include some of the hardest hit species.  Indeed, 5-6 of the 20 species of bumble bee species that occur in Wisconsin are in decline.  One species, the Rusty-patched bumble bee, has become the first federally protect bumble bee – being placed on the endangered species list in 2017. 

The endangered Rusty-patched bumble bee (Bombus affinis) collecting pollen from a wild rose at the UW Arboretum.

Bumble bees are an important pollinator of a variety of Wisconsin crops, including apples and cranberries.  Their declines, concurrent with declines in the number of honey bee colonies available, form a dark cloud on the horizon for growers, conservationists, and scientists alike.  Why are some of these once common species struggling, while some closely related bumble bee populations (such as that of the common eastern bumble bee, Bombus impatiens) increasing? 

Over the past 100 years, bumble bee declines have coincided with changes that we have made to our land.  As the intensity and footprint of agriculture has increased, supplanting the flower-rich prairies and savannas that once covered a large swath of the Midwest, a number of bumble bee species have begun to fade away.  Bumble bees, like all bees, require a diversity of pollen and nectar from flowers as their sole food source.  As flower abundance declined with agricultural expansion, the effect was felt by bumbles across the Midwest. 

However, modern agricultural landscapes are not devoid of flowers, entirely.  In fact, many flowering crops (such as cranberry, canola, and tree crops) can provide huge amounts of flowers for foraging bumble bees.  However, these flowers are only available over a short time period.  Bumble bees, unlike many smaller, solitary species, have colonies that are active much of the summer season.  As such, they require pollen and nectar from April-July/August in order to successfully produce queens for the following summer.  Our modern landscapes, in other words, have altered both when, in what quantity, and where flowers are located – with potentially dire consequences for some bumble bee species. 

Diagram of the bumble bee colony life cycle. Spring: Queen emerges and locates nest, raises first round of female workers. Early Summer: Queen stays inside laying eggs, workers forage for pollen and nectar. Late Summer: Males and new queens emerge and mate. All but new queens die. Fall/Winter: Newly mated queens dig underground to hibernate until spring.

This alteration of flower availability in space and time forms the central backbone of my research.  In pursuing an understanding of bumble bee responses to human modification of the landscape, I take a multi-faceted approach employing lab experimentation, modeling, and field observations and experiments.  Below are the various components of my dissertation work at the UW, all aimed at furthering our understanding of perhaps one of the most charismatic, and important insects groups.

1. How variability in flower abundance affects bumble bee foraging behavior

As previously mentioned, modern agricultural landscapes with flowering crops can offer large pulses of food to foraging bumble bees.  How do these pulses affect their behavior and visitation to crops?  In 2015 and 2016, I used radio frequency identification tags to measure bumble bee foraging trip duration: examining how flower availability altered foraging patterns and to test whether the type of landscape (i.e., heavily agricultural vs. heavily natural) would affect how foraging bumble bees responded to a mass-flowering crop, cranberry.  The paper describing this work was published in March 2018 in Ecological Entomology.   Please contact me if you’d like a copy.

Conceptual diagram of the RFID recording process. Tagged bumble bees leave their colony (A) and pass through a series of reading antennae (B). The tag affixed to their back is then read and recorded by a computer (C). Later, we scour the data for the correct pattern of reads (D) that denote an exit and entrance, from which we calculate the length of an individual bee’s foraging trip Inset photo shows this setup on a colony in the field.

2. Bumble bee colony development in variable resource landscapes

Summary coming soon!

3. Modeling flower abundance to predict bumble bee abundance

Summary coming soon!

4. Using historical agricultural data to understand shifting bumble bee communities

Summary coming soon!

5. Floral landscapes of tomorrow: how future landscape change might affect flower availability for foraging bees

Summary coming soon!