Dr. Rebecca Irwin is a bee researcher. And tagger. And curator. She’s also, as of 2009, a collaborator in Dr. David Inouye’s Phenology Project.
The 50-year study of the phenology of RMBL wildflowers Dr. Inouye founded has blossomed into a multifaceted exploration of flowers and their pollinators, particularly bees. While Drs. Brian Inouye and Nora Underwood now lead the team of wildflower phenology researchers, Dr. Irwin heads a group of scientists who study the phenology, diversity, and abundance of native bees around RMBL.
The Phenology Project’s overarching goal is to discover how climate change is affecting the phenology (timing of life events) of flowering plants and their pollinators. The project continues to grow in all directions. In addition to counting the flowers of more than 150 species in nine original plots plus over 12 added since 1974, the project is digging into root phenology and soil processes with research led by Dr. Aimee Classen.
Then there’s the equally long-lived dataset of billy barr’s observations of snow arrival, snowmelt, animal emergence from hibernation, temperature, and other climate measurements against which researchers can compare their data to see what trends are developing as the climate changes.
Dr. Irwin has been studying how climate warming and variation are affecting bees since 2009. After so many years she says that the flowers and bees seem like good old friends. One of the things she’s hoping to learn is how climate variation is shifting flower phenology relative to that of bees. She also wants to understand the effects of climate change on the bees’ abundance and success.
Before Dr. Irwin joined the Phenology Project as the keeper of bee data, she had been looking into pollination from the plant’s perspective, understanding how herbivores and pollinators affected plant reproduction and natural selection on flowers. But she first came to RMBL as an undergraduate student working with Dr. Kristina Jones who was studying the effects of pollinators on the natural selection of snapdragon flowers. That’s when she met Jennie Reithel, a fellow undergraduate at Middlebury College in Middlebury, Vermont.
At the time, Dr. Irwin was on an academic track to veterinary school. Once she got to RMBL, she said, “Oh my gosh, I could have a career doing this! This is way more fun!” She switched gears, steering herself towards ecology. She continued going to RMBL, doing graduate work with Dr. Alison Brody, studying the effects of nectar-robbing bees on floral traits.
Although her post-doctoral work was at the University of California-Davis, she continued spending summers at RMBL and kept returning after getting her first faculty position.
Since Dr. Inouye approached her about starting a dataset with bees mirroring his research on flowers, she has discovered more than 150 species of solitary bees ranging from Almont to the Mexican Cut Nature Preserve, along with a series of bumble bees. Every two weeks, her team samples bees at 16 sites across an elevation gradient stretching from sage brush to subalpine.
Irwin and her team catch smaller bees with bee bowls painted in fluorescent, bee-attracting colors and filled with soapy water. Larger bees, like bumble bees, are caught with a net, marked, and released. The bee-bowl captured bees are identified under a microscope, and the curated collection resides at North Carolina State University, where Dr. Irwin is Professor of Applied Ecology.
One of her team’s research goals is to understand how climate warming is affecting the time when solitary bees emerge compared to when flowers do. So far, it appears that increased temperature and early snowmelt trigger bees to emerge earlier. However, comparison of bee emergence to Inouye’s long-term flowering data suggests that bee phenology is less sensitive to climate variation than flowering phenology. This implies that climate warming has the potential to disrupt interactions between bees and their flowers.
The long-term study also looks at bumble bee abundance and asks whether climate variation affects bee abundance directly, say with changes in temperature or precipitation, or whether it’s indirect, caused by changes in flowers.
As it turns out, bumble bee abundance seems to be driven by changes in flowers, especially by very low flower abundance at the beginning of the season. That’s when bumble bees are setting up their nests. Bumble bees live in colonies, so the egg layers are queens. And during the process of laying and incubating eggs and tending to the larvae, these queens are single moms. There are no daughters around to help, so they’re working very hard to gather provisions. Early snowmelt followed by hot dry summers are very hard on larger social bees like bumble bees.
So far, Irwin and her team have found the ecosystem to be surprisingly resilient to the climate variation we have seen over the last decade. Bees may have one bad year but seem to come back the next. However, if hot, dry years continue getting hotter, what will happen to bees in the long term?
It begs the question: how can we help bees and their ecosystems adapt to a changing climate? Research and discovery at RMBL are invaluable for informing land management recommendations.
For example, on the front lines — at the level of home gardens — we can do a lot. Dr. Irwin is often asked by homeowners what they should plant to help bees and the environment.
She has a ready answer. Bump up the abundance of flowers especially early in the spring and early summer, when bees like bumble bees need all the help they can get.
Rebecca Irwin, PhD, received her bachelor of arts in biology from Middlebury College and her PhD in biology, with a concentration in ecology and evolution, from the University of Vermont. She is a professor in the Department of Applied Ecology at North Carolina State University and Consortium Director of the USGS Southeast Climate Adaptation Science Center. Her current research projects include how pollinators and pollination are responding to climate change and the management of bee parasites in natural and agricultural landscapes. She also has a long-standing interest in the exploitation of pollination mutualisms.