A group of scientists at The Scripps Research Institute has set up the microscopic equivalent of the Galapagos Islands—an artificial ecosystem inside a test tube where molecules evolve to exploit distinct ecological niches, similar to the finches that Charles Darwin famously described in “The Origin of Species” 150 years ago.
The work also demonstrates how, when given a variety of resources, the different species will evolve to become increasingly specialized, each filling different niches within their common ecosystem.
Conducted by Sarah Voytek, Ph.D., a recent graduate of the Scripps Research Kellogg School of Science and Technology, the work is intended to advance understanding of Darwinian evolution. Using molecules rather than living species offers a robust way to do this because it allows the forces of evolution to work over the course of mere days, with a trillion molecules in a test tube replicating every few minutes.
When Voytek and Joyce pitted the two RNA molecules in a head-to-head competition for a single food source, they found that the molecules that were better adapted to use a particular food won out. The less fit RNA disappeared over time. Then they placed the two RNA molecules together in a pot with five different food sources, none of which they had encountered previously. At the beginning of the experiment each RNA could utilize all five types of food — but none of these were utilized particularly well. After hundreds of generations of evolution, however, the two molecules each became independently adapted to use a different one of the five food sources. Their preferences were mutually exclusive — each highly preferred its own food source and shunned the other molecule’s food source.
In the process, the molecules evolved different evolutionary approaches to achieving their ends. One became super efficient at gobbling up its food, doing so at a rate that was about a hundred times faster than the other. The other was slower at acquiring food, but produced about three times more progeny per generation. These are both examples of classic evolutionary strategies for survival, says Joyce.