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Researcher Finds Home for Butterflies in U of C Rooftop Greenhouse

By Sam Cholke | November 28, 2012 4:56pm

HYDE PARK — Six stories above the University of Chicago campus, Marcus Kronforst nurtures tents of tropical butterflies on key lime trees and passion-flower vines.

Kronforst is one of the young academics brought onboard by the university during a period when other institutions struggled to right their budgets after the 2008 economic crisis. Leaving a fellowship at Harvard University, Kronforst set up his butterfly lab in the rooftop greenhouse above the white coats at the Pritzker School of Medicine earlier this year. He is slowly breeding the insects and searching for the genetic root of the butterflies’ myriad of bright coloration.

“These populations have only been going for the past three months,” Kronforst said, unzipping one of the five-and-a-half-foot tall tents housing a flurry of heliconious butterflies from Equador swarming around a passion-flower vine.

Kronforst, whose work was published in the esteemed scientific journal Nature, was drawn to the University of Chicago by the opportunity to set up in the research greenhouse.

“We’re pretty much at the top really,” said Greenhouse Manager John Zdenek. “I don’t know what else we could ask for really.”

The nine glass and steel chambers are all computer controlled to maintain a consistent temperature to within one degree and can precisely monitor humidity and sunlight levels.

“A greenhouse is really a machine for growing plants,” said Zdenek, who with one assistant waters and guards the research crops for university scientists. “Someone’s life work is sitting there and it’s our job to protect it.”

Zdenek must also protect outsiders from the greenhouse. Kronforst’s butterflies could ravage citrus crops if released and genetically modified plants are blasted with super-heated steam in the university’s autoclave before being thrown out.

The entrance to the greenhouse is hidden, inaccessible from the building’s elevators and main corridors. School groups are occasionally allowed up to see the university’s collection of exotic plants, but the sun lamps visible at dusk from South University Avenue are as close as most will ever get to the greenhouses.

The butterflies are a first for the greenhouse, but it’s a good fit, according to Zdenek, who waters and fertilizes the small grove of key lime trees sustaining the caterpillars.

Kronforst’s butterflies are a muddle of dominant and recessive genes that churn out generations of young with swathes of bright yellow or white banding on the wings. Kronforst is searching for the genetic mechanism that turns the coloration on and off, hoping that it will unlock our understanding of adaptation and the rise of new species of animals.

“The big question here is not about butterflies,” Kronforst said, looking in on a tent of frustrated males desperate to breed. “The real question is when we look out at nature we see all this variation, how does that come about?”

To figure that out, Kronforst must untangle the dense genetic code that dictates the species many traits and the triggers that turn those traits on and off. He has isolated the gene in the heliconious that dictates color and mating preference, but is now trying to pin down the switches that make one offspring mimic a poisonous variety while another will only make females that resemble males.

“See, that one is about to lay an egg,” he said with excitement as the female’s abdomen pulsed and popped a tiny yellow dot onto a vine.

By sequencing the genome, Kronforst has pinned the coloration variation to a single gene, which paradoxically also controls mating. The butterflies illustrate for Kronforst the accidents in life’s adaptation — a change from white to yellow may help a species survive by mimicking a toxic relative, but it also garbles the sexual preferences in the species.

Over millions of butterfly generations, those incidentally turned-on mating preferences can solidify into a new species that could no longer mate with a former relative. It’s that point-of-no-return in nature that drives Kronforst’s curiousity.

“It’s all the color patterning genes,” Kronforst said, of the butterflies he studies. “The first thing that gets everything started is the shifting in colorization.”