Genome Duplication Is a Radical — and Risky — Evolutionary Gamble

By doubling their entire genome, an organism can gain extra copies of every gene — a mutation called whole-genome duplication, or polyploidy. In most cases this is a fatal error of cell division, and only a tiny fraction of such events are thought to stabilize in a lineage. But those that do can trigger dramatic evolutionary change, according to researchers studying the phenomenon across the tree of life.

One example is Potamopyrgus antipodarum, a tiny freshwater snail from New Zealand's Lake Alexandrina. Instead of the two sets of chromosomes most animals carry, it has three or four. A team led by evolutionary biologist Maurine Neiman at the University of Iowa dated the snail's genome duplication to less than a million years ago — recent in evolutionary terms. "We actually don't know, for our snails or any other species, why this happens so reliably, again and again and again," Neiman said.

Evolutionary biologist Will Ratcliff of the Georgia Institute of Technology, who has watched yeast double its genome in long-term lab experiments, called genome duplication "a cheap and easy way to generate a bunch of heritable variation that can be then quickly repurposed for new stuff." Researchers say genome duplication events have been linked to spiders' silk-spinning organs, the large and complex brains of vertebrates, species radiations among legumes, grasses and brassicas such as broccoli and kale, and the tomato plant's fleshy fruit.

Among plants, genome duplication is hard to avoid: evolutionary biologist Jonathan Wendel of Iowa State University said all seed plants living today have experienced at least one ancient whole-genome duplication, and many have undergone more. Barnacles, insects, trout and arachnids also carry evidence of ancient duplications in their genomes. "Polyploidy is the most important process on the planet that hardly anybody knows anything about," said Douglas Soltis, a plant evolutionary geneticist at the Florida Museum of Natural History.