Endangered Iowa bee ‘poster child’ for other at-risk pollinators

This is the fifth installment of Nature’s Alarm, a series about endangered and threatened species and research in Iowa.

Erika Ibarra-Garibay trudged through vegetation in Johnson County. Some of the plants stretched taller than her shoulders. Short gasps of wind brought welcome relief as she trekked through the prairie, searching for one of its tiniest occupants.

She spotted something out of the corner of her eye. Her net arced through the cloudless sky. It landed on patch of white wild indigo. She cautiously unwound the captured insect from the mesh and secured it in a test tube. A distinct buzz resonated from the container.

“She’s a big girl,” Ibarra-Garibay, a Ph.D. student at Iowa State University, murmured as she peered into the vial.

It was an American bumblebee — a new queen, judging by her relatively unscathed wings. The species’ population has declined 51 percent in recent years. The U.S. Fish and Wildlife Service is reviewing it for potential protection under the Endangered Species Act.

It’s not the only bumblebee in peril in the United States: Populations of the rusty patched bumblebee started their descent long before. They used to buzz abundantly in 28 states throughout the Upper Midwest and the eastern United States. Since 2000, they’ve been reported in only 13 states, including Iowa. Their numbers have dropped by 90 percent. They were listed as federally endangered in 2017.

Researchers across the Midwest now are collaborating to save the endangered bees, which are essential pollinators. An ISU team is spearheading efforts in Iowa to survey rusty patched populations and learn more about their needs. The multistate project can throw lifelines for other declining bee species, too.

“There are a lot of other bees that are in just as bad shape,” said Amy Toth, project colead and an ISU professor of ecology, evolution and organismal biology. “What we're trying to do with the rusty patched is almost use it as a poster child for understanding bee and pollinator declines. … Don't forget about the other pollinators, too.”

Prized pollinator facing unclear threats

Upon first glance, the rusty patched bumblebee looks like any of the 15 other bumblebee species in Iowa. It has a chunky, furry body that’s striped yellow and black and adorned with four wings.

A closer look shows that most rusty patched bumblebees have a patch of rusty-orange hair on their abdomen, and their lower abdomen is all black. On their upper back, there’s a fuzzy patch of black that looks like an umbrella or a mushroom or a thumb tack, depending on who you ask.

Bee-pollinated crops account for about a third of the global food supply. Bumblebees in particular are “super pollinators” for commercial crops and wild native plants, Toth said. Their pollination can increase crop yields and enhance fruit quality. Some farmers and orchard owners will buy whole bee colonies for their produce.

“Wild bees will do this for free,” Toth said. “Imagine a world where you didn't have to buy bees.”

It’s still unclear exactly why rusty patched bumblebees have declined so sharply.

Habitat loss plays a large role. Bees must feed on a variety of flowers to maintain healthy diets, but such a selection rapidly has disappeared in Iowa due to agriculture and development. Those threats also put the bees’ underground nests in danger.

Agriculture almost always pairs with pesticides — another threat to bumblebees. The chemicals can impact beneficial insects in addition to their target pest species. Sprayed pesticides also can drift to adjacent areas and unintentionally harm wildlife.

Commercially raised and often exotic bee populations spread pathogens and diseases when they mix with wild bumblebee populations. Honeybees, for instance, are linked to the spread of deformed wing virus and parasites in bumblebees.

Climate change also is threatening bumblebees, which have adapted to living in colder regions. As the world warms, their range shrinks.

“You have these animals that have spent millions of years adapting to cold, and now things are heating up,” Toth said. “There is some evidence that it’s putting a lot of pressure on bumblebees in particular. Rusty patched is no exception there.”

A study in bees

Kelsey Shepherd, an ISU graduate research assistant, came to a stop in the Johnson County prairie. She placed a 1-by-1-meter frame of PVC pipe on the patch of vegetation in front of her. Then, she started jotting notes down.

“It’s a pretty grassy area,” she said, eyeing the plant species in front of her. She wore a pale yellow T-shirt with a rusty patched bumblebee printed onto it. When she was done, she looked up from her clipboard. “Now onto the next.”

Shepherd is one of the researchers that make up the ISU team studying rusty patched bumblebees. She leads the first step at each site: a rapid survey, where the team takes stock of the local habitat by analyzing nine patches of vegetation.

The team also establishes if there are any rusty patched bumblebees, briefly catching them to identify their species. The ISU team members are looking out for any American bumblebees. All in all, this part of the process takes about an hour to complete.

If a target bumblebee species is spotted, a second team — led by Ibarra-Garibay — returns to the site. They conduct a more detailed survey of the bee populations that takes around four hours.

This time, caught bees aren’t immediately released. They are put in test tubes that are then placed in ice baths for about 30 minutes. The low temperatures chill the insects into a cold-induced coma that allows researchers to take a closer look.

The team takes a variety of measurements of each immobile bee, including head width, body mass and wing deterioration. Pollen samples help reveal what plants the bees are flitting between. DNA samples hint at any interbreeding within populations. Wing asymmetry can show how much stress a bee is under.

Finally, the researchers dab the tiny insects with a pink marker to show they were already captured.

“She’s waking up already,” Ibarra-Garibay said as an American bumblebee slowly fluttered back to life on the table in front of her. Eventually, the insect flitted back off to a flower for her next meal, unaware of its role in saving her species.

A multistate collaboration

The ISU team’s project began last summer after the U.S. Fish and Wildlife Service approached them about the rusty patched bumblebee.

The species already had been extirpated in much of the northeastern United States. Targeted efforts in states like Wisconsin, Minnesota and Illinois were starting to study the bee’s dwindling populations in the Upper Midwest. Iowa was the next frontier.

Rusty patched bumblebees typically are found in Eastern Iowa. But strong, isolated populations also are found as far west as Boone County.

The ISU team completed two rounds of surveys at 43 sites last summer. The researchers detected American bumblebees at 16 of those locations. Only four sites had rusty patched bumblebees. But they all were located within or near river valleys, suggesting such habitats could be important for the species.

Now, the team is nearing the end of its two-year study. The researchers are in their third round of surveys at 44 sites. So far, they’ve detected American bumblebees at 25 sites and rusty patched bumblebees at nine.

“Last year was a relatively slow year for us. … Rusty patched just weren’t out in the numbers that people have seen them in the past,” Shepherd said. “This year, we’ve been able to detect them more — and we’re not entirely sure why.”

This summer’s extra round of surveys that stretch later into the year could be responsible, but the team won’t be sure until its analyses are complete.

The data will inform the U.S. Fish and Wildlife Service what kind of habitat management strategies best accommodate the rusty patched bumblebees. The agency can then distribute that information to partner agencies for implementation.

Anything from backyard pollinator gardens to larger habitat restorations can make a difference for supporting the species. Best of all, these efforts can help many types of beneficial insects, not just rusty patched bumblebees.

“There are things that each and every one of us can do to provide a more hospitable world to pollinators,” Toth said. “Letting things re-wild a little bit could probably help.”

Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; brittney.miller@thegazette.com