Adam Siepielski

An international team of biologists, led by University of Arkansas assistant professor Adam Siepielski, has published research indicating that climate variation likely plays a key role in shaping natural selection, the driver of adaptive evolution, among plants and animals in the wild.

“Previous evidence from other studies indicated that climate variation might be really important,” Siepielski said. “We wanted to know if we could explain variation in selection across diverse plant and animal populations through a few simple climate variables. It turns out that, yes, we can.”

Twenty biologists from the United States, Canada, Europe and Australia participated in the study, which was funded by grants from the National Science Foundation. Their work, published March 3 in the journal Science, is titled “Precipitation drives global variation in natural selection.”

The biologists assembled a database of 168 published studies that quantified natural selection over time for numerous individual populations, and among multiple populations worldwide. When matched with climate data, the resulting model showed that between 20 and 40 percent of variation in selection within studies could be attributed to local changes in precipitation.

“This is significant, especially considering the global scale of the study” Siepielski said. “These results also suggest that variation in selection is actually partly predictable based on shared climate features like precipitation. One consequence of climate change is that it is causing shifts in precipitation patterns. In many places, for example, there is more rain falling in fewer rainfall events, and in other places wide-spread drought is common.”

Changes in temperature had much less impact in the study, which was surprising, he noted. “Temperature didn’t have much explanatory power. It might act on a different temporal or spatial scale that we couldn’t pick up in the available data set”
The results don’t show exactly what effect a particular climate factor — an increase in precipitation, for example — will have across populations, he said.

“What we can’t say, as a generality, is that if precipitation increases or decreases it will result in selection becoming stronger at a global scale,” he said. “It could just as easily result in selection becoming weaker for some organisms.”

Nonetheless, the research has broad implications.
“These results show that changes in precipitation can have surprisingly quick evolutionary effects on plants and animals worldwide,” says Doug Levey, program director in NSF’s Division of Environmental Biology, which funded the research.  “Changes in temperature may also be important, but responses to them are slower.”