Genetic Diversity is Crucial for Plant Survival: Urban Cankerworm Damage

Genetic diversity is crucial for allowing a species to survive and now, scientists have a living example. Researchers have found that a lack of plant diversity is a key contributor to the widespread defoliation caused by cankerworms in cities.

Fall cankerworms (Alsophila pometaria) are caterpillars that are native to the eastern United States. They hatch in early spring and then defoliate trees and other plants, munching through the new leaves as they emerge. This can help contribute to plant death, since they're only just emerging from winter.

"We see cankerworms doing more damage to trees in cities than in the wild and examples of widespread cankerworm damage are happening more often," said Steve Frank, one of the researchers, in a news release. "We wanted to know why."

In order to find that out, the scientists looked at the lack of diversity in urban environments and the fact that urban areas have more nonnative plant species. They examined the damage that cankerworms did to understory plants, which are plants that grow near or under trees.

"I found that plant diversity plays a significant role," said Frank in a news release. "Cankerworms did more damage in simple urban environments, where the understory consisted of only a few shrubs, than they did in more complex environments with greater plant diversity."

There was also a sharp distinction between the impact on native and nonnative species. The native plants where hit particularly hard in urban environments. Instead, they benefited significantly from complex environments that more closely resembled their natural habitat. Nonnative species, in contrast, were largely ignored by the caterpillars.

"This does not mean that everyone should plant nonnative species," said Frank in a news release. "The take-home message is that we need to take steps to make urban environments more like natural environments in terms of plant diversity."

The findings reveal how important genetic diversity is when it comes to species survival.

The findings are published in the journal Urban Ecosystems.