Grasp the ongoing evolution

Charles Darwin was right.

In his 1859 book, On the Origin of Species, the famous scientist hypothesized that artificial selection (or domestication) and natural selection worked in the same way.

Now an international team, led by Northwestern University, has produced some of the earliest evidence that Darwin’s speculations were correct.

This time around, the study subjects aren’t exotic Galapagos birds, but rather a nematode, which relies on its sense of smell to gauge food availability and nearby competition. In work conducted by Northwestern, the researchers found that natural selection acts on the same genes that control the smell of wild nematodes as previously found in house worms in the laboratory.

andersen evolution
Erik Andersen

“The evolution of traits is rarely linked to exact genes and processes,” said Erik Andersen of Northwestern, who led the study. “We offer a clear example of how evolution works.”

Scientists used a combination of laboratory experiments, computational genomic analysis and field work. Their research also shows that natural selection acts on signal-sensing receptors rather than the downstream parts of the genetic process.

The study was published this week (September 23) in the journal Nature Ecology & Evolution. Andersen is an associate professor of molecular biosciences at Northwestern’s Weinberg College of Arts and Sciences.

A key model body, C. elegans is a millimeter-long nematode that lives in decaying organic matter, especially rotten fruit, and feeds on bacteria. These nematodes are typically found in gardens and compost heaps.

For C. elegans, having a keen sense of smell can mean the difference between life or death. If they smell enough food in their environment, they will stay, grow and reproduce. If they experience a food shortage and / or excessive competition from other worms, they will embark on a long and potentially fatal journey in search of a more supportive environment. This process, called “dauer”, delays growth and reproduction.

The evolution of traits is rarely linked to exact genes and processes. We offer a clear example of how evolution works.

Erik Andersen
molecular biologist

In other words, dauer reduces short-term reproductive success to ensure long-term survival.

“At some point in their lives, these worms have to make a bet,” Andersen said. “In the time it took a worm to get out of dauer and start growing again, the worm that is left has already multiplied. If the food runs out, the dauer worm makes the right decision and wins. If the food does not run out, the dauer worm loses. ”

Andersen and his collaborators have found that evolution plays a significant role in a worm’s decision to stay or enter Dauer. Some nematodes have a genetic receptor to process scents; other nematodes have two. Nematodes with two receptors have a heightened sense of smell, which allows them to better assess the availability of resources in their environment and make a better bet.

“If the worms can smell a large number of worms around them, that gives them an edge,” Andersen said. “This was discovered in a previous study on artificial selection in worms. We have now also found that it results in natural populations. We can see specific evidence in these two genes that artificial and natural selection act in similar ways. “

The study, “Niche Selection and Variation Associated with Gene Flow Shape in Pheromone Response,” was supported by a National Science Foundation Lifetime Achievement Award. Daehan Lee, a postdoctoral researcher in Andersen’s lab, was the first author of the paper.

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