New Model Shows How Behavioral Flexibility Affects Animal Evolution

When the environment changes dramatically, animals from mollusks to crows can make big changes in their behavior that enable them to survive. For example, marmots and ground squirrels in California are spending more time in wet vegetation and on steep slopes to counteract warmer temperatures. Polar bears, losing their floating ice habitats, are spending more time on land and adding bird’s eggs and reindeer to their diets. And lake trout in Ontario, which rely on external water temperatures to maintain a healthy internal temperature, shift to cooler, deeper waters and eat smaller prey when the water becomes hotter than usual.

Those behavioral changes can also speed up or slow down the evolution of species’ bodies. Yet scientists have struggled to incorporate that knowledge into their predictions of how and how quickly animals’ bodies will evolve in response to climate change. The reason: behavioral responses to a similar kind of stress can vary so much between species and even within a species. This makes it hard to extract any general patterns.

Now, Carlos Botero, an associate professor of integrative biology at The University of Texas at Austin, describes in the journal Nature Communications a new model that accounts for the impact of behavioral flexibility on evolution. He hopes it will help conservation biologists refine their assessments of how vulnerable different species are to climate change.

“By modeling the capacity to be flexible, instead of the actual behavioral responses that different animals exhibit, the model allows us to predict how and how quickly animals will adapt to climate change,” Botero said.

Using the model, Botero showed that when animals that are very flexible in their behavior are confronted with environmental change, their bodies tend to evolve slowly. 

“Evolution of the body is slow in flexible lineages not because it is more difficult but rather because it is not really needed,” he said. “For these species, behavioral adjustments take the sting out of maladaptation so there is no pressure to change.” 

To his surprise, though, when given opportunities to explore other climates and habitats, it was the moderately flexible lineages—not the ones with fast evolution and low behavioral flexibility—that were quicker at producing a larger variety of new forms and species.

As for why new forms and species can be generated more quickly in lineages that normally evolve at a slower pace, Botero said “in that case, intermediate behavioral flexibility—not too high and not too low—enables individuals to explore new habitats and tolerate a reasonable amount of environmental change without entirely preventing the need to adapt their bodies as well.”

The model Botero developed is deceptively simple, simulating how a population of thousands of individuals of the same species evolves over hundreds of generations with regards to one physical trait, for example the thickness of thermal insulation. Its predictions, however, are important and far-reaching. For example, scientists have tended to view species that evolve slowly to be at higher risk from environmental change. Botero’s findings suggest that this might not always be the case.