How Butterflies Shed Light on How Some Species Respond to Global Warming

Based on information presented at the Global Change and Global Science: Comparative Physiology in a Changing World conference, August 4-7, 2010 in Westminster, Colorado.

Jessica Hellmann and her research team at Notre Dame have conducted a series of studies in which manipulating the temperature of the butterfly larvae's environment revealed how the two species might respond to global warming.

Photo: Anise swallowtail caterpillar (Papilio zelicaon)
courtesy of Shannon Pelini.

The team studied the larvae--or caterpillar phase--of two butterfly species, the Propertius duskywing butterfly (Erynnis propertius) and the Anise swallowtail butterfly (Papilio zelicaon). These butterflies, both cold-blooded insects, were chosen because of their ecological differences but they live in the same ecosystem, allowing Dr. Hellmann to compare their responses in a single study.

They found that in summer conditions, the duskywing larvae grew bigger, faster, and they survived better, which suggested that they liked it warmer, but winter was another story. "In the warmer winter, they increased metabolism and burned through energy faster. This suggests that they were adapted to the cooler winters of Vancouver," according to Hellman, via a press release issued by the American Physiological Society.

As for northern swallowtails in central conditions, "They just didn't care. They didn't respond to warming at all. They didn't do better or worse. This means that assumptions about warming possibly benefiting species [with more spread out genes], particularly at the northern edge of the range, are not appropriate."

What's next for the team? They've begun studying the genetic explanation for how the two species respond to warming. They are investigating what genes are responsible for the individualized responses, and will use genomic tools to learn which genes are involved when the species is experiencing climate change. They'll also try to determine which genes these butterflies are synthesizing when they experience climate warming. We want to know if northern and southern members of the same species are expressing their genome differently or the same. Hellman thinks the answers may explain the differences between various populations of the same species--northern vs. central--and why some species might not be inclined to relocate as the climate heats up.

Who knew?