Guest Contributor

**Kaya Wurtzel**
Bowdoin ‘21

Before I talk about this week’s paper, I want to acknowledge that Breonna Taylor would have celebrated her 27th birthday today. Instead, we’re still waiting on the arrests of police officers who shot her, after entering the wrong house in the middle of the night. Breonna was a daughter, a friend, and a first responder—her life mattered, and she should still be here. Breonna’s murder is just one of the recent incidents of police brutality driving Black Lives Matter protests across the country and world. Systemic racism and white supremacy are not just present in our police force--they also permeate just about every part of our society, including Ecology, Biology, and Bowdoin. Black folks are underrepresented in our field, and we have work to do, unpacking white supremacy, to make our communities safe to heal, learn and grow for everyone. This is a long-term process, but, for today, I’ll start by sharing this collection of podcasts, featuring storytelling by Black scientists. Black stories matter, black scientists matter, and black lives matter.

Can bumblebees stimulate flower production by damaging leaves?

Each spring, bumblebees establish new colonies and have an increased demand for floral resources. Pollen availability during this period can have long term implications for the health of the colony. Under changing environmental conditions, bees may begin establishing new colonies earlier in the spring, when floral resources are still scarce. A recent paper published in Science based on work in the De Moraes Lab, at the Swiss Federal Institute of Technology, suggests that bumblebees may be able to accelerate local flower production by damaging leaves of flowerless plants.

After observing Bombus terrestris damaging plant leaves without feeding on or collecting any leaf material, Pashadilou et al. hypothesized that leaf-damaging behavior could induce flower production. Previous work has shown that abiotic stressors can induce flowering but little is known about the effects of biotic stressors, like insect leaf damage.

To test whether B. terrestris leaf damaging behavior induced flowering, researchers exposed flowerless tomato and black mustard plants to pollen deprived B. terrestris colonies. They allowed worker bees to make 5-10 leaf holes and then removed the plants. Each bee damaged plant was paired with a mechanically damaged plant, where researched tried to precisely copy bee leaf damage using forceps and a razor. They found that bee-damaged tomatoes flowered an average of 30 days earlier than undamaged plants and 25 days earlier than mechanically damaged pants. Bee-damaged black mustard plants flowered an average of 16 days earlier than undamaged plants and 8 days earlier than mechanically damaged plants. The results of this first experiment indicate that B. terrestris leaf-damaging behavior induces earlier flowering but do not establish the mechanism at work.

In a series of following experiments, Pashadilou et al. evaluate the influence of pollen availability on leaf-damaging behavior. Laboratory experiments found that rates of leaf-damaging behavior were significantly higher for bees under pollen limitations. Subsequent rooftop studies found that the frequency of damaging behavior declined as local flower resources increased in the spring. When the rooftop study was repeated with the addition of a path of flowers adjacent to the hive, the frequency of damaging behavior decreased. In a final rooftop study in 2019, Pashadilou et al. compared two rooftops: one where B. terrestris hives had access to a patch of flowerless plants and another where hives had access to a garden of wildflowers and a patch of flowering plants, adjacent to the patch of flowerless plants. Bees damaged plants in both flowerless patches but at higher rates on the rooftop without nearby floral resources. When they mowed the flower gardens on the second roof, bee damage rates on the flowerless patch increased significantly. Over the course of the rooftop experiments, researchers also observed wild B. lapidarius and B. lucorum damaging flowerless plants. These rooftop studies demonstrated that local pollen availability influences leaf damaging behavior, even when bumblebees have the option to forage farther away.

Altogether, the results of this study suggest that multiple species of bumblebees, including B. terrestris, B. lapidarius and B. lucorum, use leaf-damaging behaviors to accelerate local flower production, especially when floral resources are scarce. In the face of environmental change threatening our pollinators, these findings highlight the potential for adaptation and resiliency of plant-pollinator interactions.

Kaya Wurtzel

Bowdoin ‘21

Jones Lab Student Researcher