How do invasive plants facilitate disease?

Foliar fungal disease on an invasive grass.

Motivation

When species are transported across their natural dispersal boundaries, they often leave behind specialist enemies. This can give them a competitive advantage over native species, contributing to them becoming invasive. However, invasive species can then accumulate enemies over time. Newly accumulated enemies may suppress invasive species or spillover to native species. It is unclear what the long-term impacts of accumulated enemies are on invasive species and their interactions with native species.

Approach

I explored the consequences of disease emergence on a grass species, Microstegium vimineum, which is invasive in the U.S. The disease is caused by fungi in the genus Bipolaris My research questions included:

  • Does plant origin and life history influence the composition and impacts of fungal diseases?
  • How much does disease transmission depend on the invasive species and native species?
  • What are the effects of disease on the invasive species and native species?
  • How does disease mediate competition between the invasive species and native species?

I completed this research as a postdoc in the Agronomy Department at the University of Florida (UF), advised by Luke Flory. We collaborated with ecologists (Keith Clay - Tulane University and Chris Wojan - University of Indiana), plant pathologists (Erica Goss, Phil Harmon, Brett Lane, and Ashish Adhikari - UF), and theoreticians (Bob Holt, Mike Barfield, Nick Kortessis, and Maggie Simon - UF). We also collaborated with ecologists at Standford University conducting similar research in grasslands (Erin Mordecai, Caroline Daws, and Erin Spear). Undergraduate researchers and field scientists that led and contributed to this work include Liliana Benitez, Zobia Chanda, Laney Davidson, Katelyn Doyle, Riley Dunlop, Trevor Green, Mariam Higginbotham, Zadok Jollie, Evan Lacey, Daniela Menendez, David Notman, Teresa Orosa, Shannon Regan, Penny Reif, Callie San Antonio, Vida Svahnström, Thomas Thrasher, Ryan Truesdell, and Max Zaret.

To address these questions, I led a two-year field experiment in Indiana at Big Oaks National Wildlife Refuge. I used data from that experiment and one in California as well as dynamical models. Statistical approaches included generalized linear models, PERMANOVA, Bayesian hierarchical models, and structural equation models.

Key findings

  • Non-native annual grasses host distinct fungal pathogen communities from native perennial grasses and are less susceptible to pathogen damage (Kendig et al. 2021 Journal of Ecology).
  • Disease transmission depends on live and dead biomass of the invasive species (Benitez et al. 2022 Ecosphere, Kendig et al. in prep).
  • Disease negatively affects the invasive species and native species, but native species vary in their tolerance (Kendig et al. 2021 PLoS ONE, Kendig et al. in prep).
  • Disease emergence can increase the impacts of the invasive species on native species by decreasing the native species' carrying capacity (Kendig et al. in prep).
Amy E. Kendig
Amy E. Kendig
Postdoctoral Researcher

ecologist and data scientist specializing in human impacts in plant communities