

Carbon dioxide gas is pumped into half of the transparent, plastic-covered boxes to simulate the atmosphere that's likely to exist more than a century from now if levels of the heat-trapping greenhouse gas continue to rise due to the burning of fossil fuels.

Milkweed plants from the chambers were fed to hundreds of monarch caterpillars this summer. Milkweed is a monarch caterpillar's only food, satisfying its nutritional needs while providing an invaluable medicinal boost. The plant's leaves contain a bitter toxin that helps the insects ward off predators and parasites.

But previous work at U-M's northern Michigan biological outpost, in the laboratory of ecologist Mark Hunter, showed that some species of milkweed produce lower levels of the protective toxins, called cardenolides, when grown under elevated carbon dioxide conditions.

That finding caught the attention of U-M doctoral student Leslie Decker, who with Hunter designed a multi-year follow-up study, underway at the Biological Station, that is the focus of her dissertation in the Department of Ecology and Evolutionary Biology.

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Currently Michigan News feature story