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Powerhouse plants

UD researchers identify key native plants that support shrinking number of insects, stabilize food webs

by | December 10, 2020

Photos by courtesy of Doug Tallamy

Dec 10, 2020

UD’s Doug Tallamy (left) is a professor of entomology, conservationist and bestselling author. He researches how native plants are crucial to the food web. Insects are the important parts of the web, including the spun glass caterpillar seen here eating a leaf on an oak tree.

University of Delaware Professor of Entomology Doug Tallamy published a new research study in Naturethat systematically identifies the most critical plants needed to sustain food webs across the United States. Alongside co-authors Kimberley Shropshire and former graduate student Desiree Narango, now a postdoctoral researcher at the University of Massachusetts Amherst, the study drills down to the top plants in each county and bioregion, illuminating a plan for how to restore ecosystems anywhere in the country. 

Why care about food webs? Well, these complex, highly interconnected systems of feeding relationships are essential for our planet’s health. The Earth and its many species depend on them, including humans.

To get the feast started, who has the first seat at the dining room table? The system all starts with plants, which get great publicity for their ability to convert carbon dioxide and into breathable air. But plants also have another, lesser known talent; they capture energy from the sun and turn it into food. Animals eat plants. Some eat plants directly; others obtain this energy by eating an animal who eats plants. And what animals are the best at converting this energy? Think small. 

Punching way above their weight class, insects are the best creatures on Earth at this energy transfer. And the world champions are caterpillars of the Lepidoptera species, the lifeblood of the food web whose protein-rich bodies are ideal for hungry birds.

But caterpillars and other insects can’t simply thrive among any plants; they must be surrounded by native plants, meaning those that have evolved alongside insects over millions of years. For example, caterpillars in Delaware like the promethea silkmoth don’t jive with popular exotic trees like crepe myrtle, a popular choice by homeowners. 

And not just any native plant will do. The new research finds that only a few powerhouse plants support the majority of Lepidoptera. Ninety percent of what caterpillars eat is created by only 14 percent of native plant species with only five percent of the powerhouse plants taking credit for 75 percent of food.  This pattern is consistent wherever you go in the U.S. 

“Most people talk about a food chain as if it’s linear. In a diagram, these connections look like a web rather than a simple chain,” said Tallamy, a conservationist and bestselling author. “Take a keystone native plant like an oak tree. More than 500 types of caterpillars can eat that oak tree. That allows for a more complex and, thus, more stable food web.”