When she set out to understand whether climate changes over the past century were affecting insects’ patterns of eating and damaging various plants, Emily Meineke decided to go straight to the source: the vegetation samples.
A postdoctoral researcher working in the lab of Charles Davis, professor of organismic and evolutionary biology and director of the Harvard Herbaria, Meineke is the lead author of a first-of-its-kind study that used herbarium specimens to track insect herbivory (the eating of plants) across more than 100 years. The study is described in a Sept. 4 paper published in the Journal of Ecology.
The paper is co-authored by Aimée Classen and Nathan Sanders, who are affiliated with the University of Vermont and the Gund Institute for Environment, and Jonathan Davies, an associate professor at the University of British Columbia.
Across four species — shagbark hickory (Carya ovata), swamp white oak (Quercus bicolor), showy tick trefoil (Desmodium canadense), and wild lowbush blueberry (Vaccinium angustifolium) — the study found that specimens collected in the early 2000s were 23 percent more likely to be damaged by insect herbivores than those collected in the early 1900s.
The data also showed that insect damage was greater following warmer winters and at low latitudes, Meineke said, suggesting that higher temperatures driven by climate change could be a factor driving insect damage.
“The overwhelming pattern is that across these four different plant species, with different life histories, insect damage is increasing over time,” she said. “In New England, it appears that warming in winter is an important factor driving insect herbivory damage overall.
“Knowing that insect damage on these plants is increasing is useful because we might be able to come up with management strategies before it reaches economic levels,” she continued. “I think this study is the tip of the iceberg. Now that we know these plants have more damage than they did 100 years ago, we can try to understand what that actually means for plants.”
To understand whether herbivory was increasing, Meineke and colleagues developed a detailed system for measuring not just whether specimens showed insect damage, but how much.