Catherine Linnen: What Underlies Diversity
Assistant professor, University of Kentucky
Recommended by Hopi Hoekstra, Harvard University
When she was little, Catherine Linnen liked picking up whatever bugs or lizards she could find outside. And so it was only natural that she grew up to study the diversity of the natural world.
"I always liked living things and thought they were fascinating," she said.
In particular, Linnen is now curious about the genetic mechanisms underlying that diversity and how species adapt. Her work currently focuses on two natural populations: deer mice and pine sawflies.
After the glaciers retreated in North America some 8,000 to 10,000 years ago, mice moved into the Sand Hills region of Nebraska and adapted to that environment. Mice living there have lighter coats and a different tail stripe pattern than other mice. In this system, Linnen and her colleagues are exploring the genes and mutations responsible for the mice adapting to that environment.
Similarly, the pine sawflies have adapted to different host pine trees — including one that was introduced to North America within the last couple of hundred years — and she and her colleagues are studying the mechanisms driving that adaptation.
"There [are] all these traits that are variable, so we can go in and ask why that variation is there, what are the selective pressures they are responding to, but also what are the genetic mechanisms underlying that," Linnen said. She added that they can examine whether the organisms use the same genes and mutations each time or whether they find different solutions to the same problems.
A challenge, Linnen noted, is that while the field is getting better and better at generating sequencing data, advances in bioinformatics aren't keeping pace. "It's always a challenge to play catch-up and try to figure out how to analyze your data once you get it," she said. "It could be terabytes and terabytes of data and you have to figure out how to deal with that data and I think that is a challenge for a lot of us."
Paper of note
In Science earlier this year, Linnen and her colleagues reported that adaptation in the deer mice in the Nebraska Sand Hills is due to a number of mutations in a single gene.
While they uncovered that the light fur was due to a mutation in the Agouti gene, they also noted that the Sand Hills and wildtype mice differ at a number of pigmentation traits. For example, the Sand Hills mice have a lighter ventrum and the boundary between the dorsal and ventral sides of the mice are shifted upward.
All of these traits were linked to the Agouti gene, and by examining a number of mice from that area, they found that the mice have multiple mutations in the Agouti gene that contribute to the Sand Hill phenotype.
"If you just look in lab, it looks like it is all due to a single gene, but then if you go out in nature and really carefully dissect that, it turns out that it is due to all multiple mutations in the same gene," Linnen said. "It's sort of one of these things where if we hadn't stepped outside of the lab and gone back into nature, we would've drawn a totally wrong conclusion."
Looking ahead
In the future as sequencing technology continues to improve, Linnen said that more and more biologists who have been studying non-model organisms systems will be able to take advantage of those tools. From this, she said researchers will be able to glean more about evolutionary adaptation.
"We're seeing this increasing ability to go out after these natural systems where we know more about actual biology and ecology, and we can apply these tools to get a much deeper understanding about how evolutionary processes work," she added.