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Pathogens and Plant Invasion Ecology

Explore the interplay between pathogens and invasive plants, their impact on biodiversity, ecosystem effects, and mechanisms of introduction. Understand the traits that make a species invasive and the role of pathogens in plant invasions, with a focus on ecological risks and management approaches.

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Pathogens and Plant Invasion Ecology

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  1. Pathogens and Plant Invasion Ecology

  2. What do invasive plants have to do with us?

  3. What do invasive plants have to do with us? • Framework for study of pathogen invasions

  4. What do invasive plants have to do with us? • Framework for study of pathogen invasions • Pathogens’ role in plant invasions

  5. What do invasive plants have to do with us? • Framework for study of pathogen invasions • Pathogens’ role in plant invasions • Mechanism for introduction of pathogens

  6. Invasive species: The second biggest threat to biodiversity today. (Vitousek et al. 1997) Photo: Charles Webber, California Academy of Sciences

  7. Ecosystem Effects • Soil chemistry/nutrient cycling

  8. Ecosystem Effects • Soil chemistry/nutrient cycling • Fire frequency & intensity

  9. Ecosystem Effects • Soil chemistry/nutrient cycling • Fire frequency & intensity • Hydrology & sedimentation

  10. Ecosystem Effects • Soil chemistry/nutrient cycling • Fire frequency & intensity • Hydrology & sedimentation • Erosion

  11. Effects on Biota • Displacement of native species • E.g., ice plant and native shrubs

  12. Effects on Biota • Displacement of native species • E.g., ice plant and native shrubs • Hybridization with native species • E.g., Spartine alterniflora and S. foliosa

  13. Effects on Biota • Displacement of native species • E.g., ice plant and native shrubs • Hybridization with native species • E.g., Spartine alterniflora and S. foliosa • Promote (or introduce) non-native animals & microbes • E.g., Myrica faya in Hawaii

  14. What makes a species invasive? • “The ability to increase when rare.” (Crawley 1997)

  15. What makes a species invasive? • “The ability to increase when rare.” (Crawley 1997) • …Well, duh. So what makes a species likely to be a problem?

  16. A cautionary tale: Baker’s traits and USDA GMO deregulation • Keeler (1989) suggests using Baker’s traits as predictor of weed risk in GM crops • Williamson (1994) proves this method has little/no predictive value • As of 1997, APHIS continues to accept list as only evidence to discount ecological risk in petitions to deregulate crops

  17. Invasible Ecosystems • Disturbed areas • Ports of entry • Community composition/diversity

  18. Pathogens’ Role • Natural Enemies Hypothesis: plants leave enemies behind; are better competitors

  19. Pathogens’ Role • Natural Enemies Hypothesis: plants leave enemies behind; are better competitors • Biotic Resistance Hypothesis: native pathogens prevent new plants from establishing

  20. The Enemy Release Hypothesis

  21. Problems with Empirical Model • Beneficial associations: • Natives • Exotics • Biotic resistance

  22. Gilbert & Parker, UCSC Photos: I.M. Parker, UCSC

  23. California Coastal Clovers • 7 exotic, 9 native • Beneficial association with fungal endophytes in 2 most invasive • Leaf spot (Lesptosphaerulina, Pseudopeziza, Phoma) most severe on exotics (BR) • Leaf necrosis (Stemphylium)slightly more severe on natives (NE) • Damping-off most severe in natives (NE)

  24. Introduced plants can bring their pathogens • Chestnut Blight • Dutch Elm Disease • Phytophthora infestans

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