Laura Burkle and her colleagues captured 2,778 bees while retracing the muddy steps of a scientist who studied the interactions between bees and flowering plants more than a century ago.
Occasionally stung, but considering herself lucky to have access to the rich historic records that guided her field work, the Montana State University ecologist and her collaborators have now published their results in the journal Science.
Burkle conducted her bee study in the forests of southern Illinois while she was a postdoctoral researcher at Washington University in St. Louis, Mo. Now at MSU for the past two years and planning a major ecological study between Yellowstone National Park and Glacier National Park, Burkle and her co-authors compared the bees and flowering plants that existed in 2009 and 2010 with those that existed in the late 1800s and early 1900s around Carlinville, Ill.
The researchers discovered that the area has lost many species of bees and flowering plants over the 120 years since professor Charles Robertson first surveyed the area, Burkle said. Also lost were many interactions between the bees and flowers.
Despite the loss, however, the bees and plants have been surprisingly resilient in the face of warmer temperatures and changing land use, Burkle said. The forests that once grew 10 miles outside of Carlinville are fragments of what they were when Robertson drove his horse and buggy to collect specimens. Fields of corn have replaced acres of trees and prairie. Natural areas have been converted to agricultural, commercial or residential uses. Winter and spring temperatures have risen an average of 3.6 degrees Fahrenheit.
"The good news is that these systems and the way they are structured make them really resilient to change," Burkle said. "But there's been so much change that resiliency has been compromised."
Co-author Tiffany Knight, Burkle's faculty adviser for the study, said, "Plants are an important resource for humans, providing food, fiber and the backbone for all other ecosystem services. Most plants rely on animal pollinators for their reproduction. There is concern that human changes to the environment are disrupting plant-pollinator interactions, but our study is the first that has been able to look at this problem using historical data.
"One of our significant findings is that climate change has resulted in mismatches between plants and their historic pollinators, such that insects are active during times when plants are not in bloom," Knight said. "This is likely because plants and insects respond to different environment cues, and thus, we expect that mismatches between plants and their historic pollinators due to climate change is important across the globe."
The scientist who inspired the recent study was a Harvard professor before moving to Illinois to retire. When he discovered the woods around Carlinville, however, he resumed his academic life as a professor at the local Blackburn College. He collected most of his data from 1887 to 1897, but continued into 1917.
"He loved it," Burkle said. "That was his full-time passion."
Burkle learned about Robertson while looking for a research project to pursue as a postdoctoral researcher. Since Carlinville and St. Louis are just 1 ½ hours apart, Burkle and Knight decided to follow up Robertson's study with their own.
They spent the springs of 2009 and 2010 doing fieldwork around Carlinville. Generally working in the woods between 9 a.m. and 3 p.m. when bees are most likely to fly, the researchers slogged through the forests looking for the first flowering plants of the season. Then they captured the bees that pollinated those flowers and identified them under the microscopes Burkle set up in their Carlinville apartment.
In 477 hours over two years, the researchers collected 3,620 "floral visitors," Burkle said. Of those, 2,778 were bees and the rest were mostly flies and butterflies. The plant that attracted the largest number of bees -- 923 individuals and 33 species -- was Spring Beauty, a small herbaceous plant. Second most popular plant was the Great Waterleaf.
In addition to their and Robertson's specimens, Burkle and Knight compared their findings to those of co-author John Marlin from the University of Illinois. Marlin, who had gathered data from the Carlinville area in the 1970s, provided intermediate-year information that was "incredibly helpful," Burkle said.
Burkle conducted her research with a $75,000 RAPID grant from the National Science Foundation.
Burkle's next study will begin this summer and look at disturbances -- such as from recent and more historic fires -- to see how plant and pollinator communities re-assemble across Montana between Yellowstone and Glacier national parks.
The suite of species that live in Montana and Illinois are entirely different, but some of the same issues apply, Burkle said.
Knight said, "I would expect that the effects of climate change on plant-pollinator interactions are even greater in some locations, such as high elevation sites in the Rocky Mountains that have experienced more dramatic changes in climate than our Midwestern site."
She added that Burkle's expertise on identifying bees and analyzing plant-pollinator networks were crucial to the success of the bee project.
"I miss working with her at Washington University, but I think she is in an excellent location to make new and significant contributions to the field of pollination biology," Knight said.
- Laura A. Burkle, John C. Marlin, and Tiffany M. Knight. Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence and Function. Science, 28 February 2013 DOI: 10.1126/science.1232728
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