Forest ThreatNet

Volume 13, Issue 1 - spring 2020

Tree diversity regulates nonnative pest invasions in forest ecosystems

HWA_bugwoodNonnative pests often cause ecological impacts with multiple socioeconomic costs. Understanding how plant diversity may influence insect and disease invasions could help resource managers minimize negative impacts. High species diversity may facilitate pest invasions by providing a wider variety of ecological opportunities, but it can also dilute invasion success because low host abundance may make it more difficult for pests to establish. New continent-wide research led by Forest Service scientists including Theat Center scientist Qinfeng Guo, and published in the Proceedings of the National Academy of Sciences, indicates that tree-pest diversity relationships are hump-shaped. Pest diversity increases with tree diversity at low tree diversity levels (due to facilitation or amplification) and is reduced at higher tree diversity (due to dilution). Thus, tree diversity could regulate forest pest invasion in these two different ways simultaneously, but their relative strengths vary with overall diversity. These findings show that the role of native species diversity in regulating nonnative pest invasions is more complex than previously understood. Read more about this research.


Pictured: An example of forest pest invasion: nonnative Hemlock woolly adelgid (Adelges tsugae). Hemlock trees grown under sunnier conditions may be more likely to survive infestations. Photo by Chris Evans, courtesy of the University of Illinois and

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