Species facing widespread and rapid environmental changes can sometimes evolve quickly enough to dodge the extinction bullet. Populations of disease-causing bacteria evolve, for example, as doctors flood their "environment," the human body, with antibiotics. Insects, animals and plants can make evolutionary adaptations in response to pesticides, heavy metals and overfishing.
Previous studies have shown that the more gradual the change, the better the chances for "evolutionary rescue" the process of mutations occurring fast enough to allow a population to avoid extinction in changing environments. One obvious reason is that more individuals remain alive when change is gradual or moderate, meaning there are more opportunities for a winning mutation to emerge.
Now University of Washington biologists using populations of microorganisms have shed light for the first time on a second reason. They found that the mutation that wins the race in the harshest environment is often dependent on a "relay team" of other mutations that came before, mutations that emerge only as conditions worsen at gradual and moderate rates.
Without the winners from those first "legs" of the survival race, it's unlikely there will even be a runner in the anchor position when conditions become extreme.
"That's a problem given the number of factors on the planet being changed with unprecedented rapidity under the banner of climate change and other human-caused changes," said Benjamin Kerr, UW assistant professor of biology.
Kerr is corresponding author of a paper in the advance online edition of Nature the week of Feb. 9.
Unless a species can relocate or its members already have a bit of flexibility to alter their behavior or physiology, the only option is to evolve or die in the face of challenging environmental conditions, said lead author Haley Lindsey of Seattle, a former lab member. Other co-authors are Jenna Gallie, now with ET
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University of Washington