Study examines climate's role on ecosystems

As climate change affects a particular organism, how will this affect ecosystems? Do groups of organisms respond in the same way to major environmental changes, or do individual organisms each respond differently?

Willamette University biologist Christopher Smith studies the co-evolution of Joshua trees and yucca moths. His recent study in PLoS ONE addresses longstanding questions about how ecosystems respond to climate change and the role of species interactions in shaping those responses.

During the 20th century, scientists debated how often organisms will respond in a consistent manner to ecological and environmental changes. The data seemed to suggest that the interdependence of species was limited. In response to climate change, some species might migrate to more suitable habitats while others stay in place. This “individualistic” model of ecological communities became the scientific consensus.

Smith and the study’s co-authors present evidence that the issue may not be so clear cut. By looking at genes, climate models and well-preserved plants from packrat burrows, scientists can determine how ecological communities have responded to major environmental changes over tens or even hundreds of thousands of years.

Using these techniques, Smith found genetic signatures that indicate the populations of Joshua trees and four species of yucca moths all experienced dramatic growth at the same time – about two hundred thousand years ago. The patterns are so consistent from species to species that it’s very unlikely to be a coincidence.

“We’re looking at a group of organisms that are highly interdependent, so the discovery that they all shared a common history of population growth is, on its own, not too surprising,” said Smith. “What is exciting, however, is that this type of pattern may be more common than we first thought.

“Because the world is mostly composed of small organisms that interact strongly with other species – such as plant-eating insects and fungi that parasitize other organisms, like those we studied – the individualistic model of communities might not apply to every case.”

The work has potential implications for evaluating the effects of climate change. If organisms tend to respond in concert to environmental change, then it may be easier to predict the effects of global warming on whole ecosystems.