4:15 p.m. - Of Mice and Mammoths

The last talk of the day (for me, as I had to leave before the final, final talk) made for a great reminder of how far the field of evolutionary biology, wrapped in a relatively simple story told engagingly by Hopi Hoekstra of Harvard. Hoekstra described her research quest as “the hunt for genes that make a difference,” and she uses a really nice model system - the oldfield mice of the southern United States. These mice typically are brown in color, but they have migrated in the recent (meaning thousands) of years to the gulf and atlantic coasts and taken up residence, like a retired couple, on the beach. But a brown mouse on a beach is a target, and their predators, which include birds and coyotes, find it all to easy to locate their brown fur on white sand and make a beachside snack out of them.

Cue natural selection - soon you have brown oldfield mice inland, and predominantly white oldfield mice that live on the beach. Hoekstra tested whether the fur color really does construe an evolutionary advantage with a simple experiment - make a bunch of clay mice colored brown or white, and leave them out on the beach. Sure enough, the brown clay mice quickly showed divots and bitemarks left by attacks from (presumably very frustrated) predators.

That would have been a fine experiment for the 1959 conference, but Hoekstra’s next step was pure 2009 - she took examples of brown and white mice back to the lab, bred them, and searched for the genes that determined fur color. Her laboratory narrowed the gene candidates down to three genes, and in one of them - a receptor called Mc1r - the substitution of a single amino acid flipped the switch from brown fur to white fur. Amazingly, when another group of scientists sequenced the genome of extinct mammoths in 2006, they found the same amino-acid substitution in the same gene, implying that mammoths, like the oldfield mice, came in different color varieties.

After so much high theory and methodological complexity, Hoekstra’s experiment sent all of us (or at least me) home with a warm feeling - not only was her experiments a beautiful example of evolutionary biology that would have been impossible in 1959, it was a great example of teachable science, the kind of story that a 3rd-grader could wrap their head around and begin to see the truth of evolution. The cloud hanging over Darwin/Chicago 2009 was the uneasy feeling that all this scientific progress was still losing out in the arena of public opinion, but Hoekstra’s work and charismatic speaking style (on the heels of similar ambassador figures Neil Shubin and Michael Shue) chased away some of the pessimism, and left me confident that the more examples we find of Darwin’s elegant theory at work in nature, the easier it will be to convince the world that it is true.

And with that, we’re finished. Happy Halloween to those of you who have followed me this far, and thanks very much for reading and perhaps linking to the posts. I’ll be back Monday with a digest post to help navigate the coverage of the last few days, and Jeremy Manier will be here Tuesday with his own thoughts on the conference.

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A relatively simple food web, believe it or not. (from Allesina & Pascual, 2009)

Ecologists drifted long ago from the simplistic model of the food chain to food webs, intricate, multi-tendril interactions between species that paint a more accurate picture of an ecosystem’s network. But, as with most sciences, as the models become more complex, so too does the analysis required to answer questions about the role each animal plays in an ecosystem. In a chain, if you remove one piece, the whole network falls apart. But how do you rank the importance of organisms in a system that looks like the tangle of wires behind an entertainment center?

Stefano Allesina, a brand new assistant professor in the University of Chicago Department of Ecology & Evolution (like, really brand new, as in moved into town last week) found the answer to this question in a brand name rapidly taking over our lives: Google. Specifically, he got a hunch that the algorithm Google uses to operate its search engine could be turned into a tool for detecting what species are most integral to an ecosystem’s health.

“One of the main problems in conservation is to forecast what’s going to happen if the species we are looking at is going down or going toward extinction,” Allesina said. “This single extinction can cascade in the loss of other species that are apparently unrelated, because all things are interdependent and it’s a very complex machinery. Or you could take away one piece and maybe the whole thing will reshape itself.”

So Allesina, and his collaborator Mercedes Pascual from the University of Michigan, constructed a computer model, published earlier this month in PLoS Computational Biology, to find vulnerabilities in an ecosystem. As Allesina describes it, they tried to help the cause of conservation by looking for the best way to destroy an ecosystem.

“How can we damage the network in the fastest possible way? How can we take away the most important species first so we can make the whole system collapse? It’s the best solution, but it’s actually not very good for the environment,” Allesina laughed.

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