Herbivores Combat Invasive Species in Diverse Plant Communities

Herbivores, like caterpillars, play a major role when it comes to protecting habitats from invasive species. Now, scientists have taken a closer look at their impact, stressing their importance in ecosystems across the globe.

Diverse plant communities actually tend to resist invasion by non-native plants. Yet why exactly this is the case has remained uncertain. That's why the researchers decided to take a look at the role of herbivores in this particular case.

The scientists examined herbivore damage on leaves of non-native oak trees in arboreta across the United States. Surprisingly, they found that non-native oaks in regions with high oak species diversity showed more leaf damage than those in regions with low diversity.  

"Competition for resources has often been thought to limit invasions in diverse plant communities, but herbivory could also limit these invasions," said Ian Pearse, lead author of the new study, in a news release. "Diverse plant communities are more likely to contain herbivores that are able to consume a non-native species, which may help to explain why diverse communities are able to resist invaders while others are easily dominated."

While native oaks still suffered more leaf damage that non-native oaks overall, in the absence of native oaks, non-native oaks showed even less leaf damage. This, in particular, shows that diversity can help encourage herbivores to chomp down on invasive species.

The findings reveal a bit more about how herbivores play such a vital role in combating invasive species. More specifically, it shows how protection of intact plant communities and their associated herbivores may become critical to guarding against non-native species.

The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.