0. Fluctuating Resources: A General Theory of Invasibility
By: Megan Murphy, Sarah Brodeur, Lauren Bettino, Jenna Del Buono, and Keith Green

1. Original Paper
Fluctuating resources in plant communities: a general theory of invasibility
By:
Mark A. Davis, J. Philip Grime and Ken Thompson
Published In Journal of Ecology, 2000

2. The Theory
Communities are more prone to invasion as a direct result of the presence of excess unused resources.

3. The Theory
Invasibility increases when there exists a difference between gross resource supply and total resource uptake
Resource supply/availability can increase due to:
A pulse in resource supply
A decline in resource uptake
A combination of both

4. Background Invasions are influenced by three general factors:
Propagule pressure
Invasive species characteristics
Invasibility of new environment
→ Considerations: competitive abilities of resident species, presence (or absence) of herbivores, pathogens, and/or mutualists, facilitative effects of resident vegetation, and disturbance regimes

5. Background Resources that may contribute to susceptibility:
Phosphorus and nitrogen levels
Precipitation levels
Global environmental changes (CO2)
Pronounced fluctuations of resource supplies
Factors that DO NOT contribute to susceptibility:
Community diversity
Average community productivity

6. Background Designed experiment: controlled grassland plots
Tested: effects of varying disturbance and fertility gradients on invasions
Results:
Increased disturbance = increased invasions
Increased fertilizer = increased invasions

7. Literature Review / Methods
Keyword search using Web of Science and Google Scholar
Found 1192 papers, reviewed 43
Looked specifically at:
The invasive species, taxonomic group, type of invaded ecosystem, and whether or not the results of the article matched our hypothesis

8. Does the literature support the fluctuating resources hypothesis?

9. Taxonomic groups that follow the fluctuating resources hypothesis

10. Kercher & Zedler: Phalaris arundinacea L.
Designed experiment: controlled mesocosms
Tested: effects of light availability, nutrients levels, flooding (disturbance) on invasions
Results:
Increased nutrients = increased P. arundinacea
Increased light = increased P. arundinacea
Most rapid invasion during max levels of both nutrients and light at once
Increased flooding = increased P. arundinacea
P. arundinacea; Reed canary grass

11. Discussion Hypothesis IS well supported
Bias/point of error: different number of articles reviewed for each taxonomic group
Terrestrial plants support hypothesis 71% of the time
Aquatic plants support hypothesis 83% of the time
Pathogens and insects support hypothesis 100% of the time
NO mammals included
Article states how invasions affect wide range of habitats - matches our data
Many references to the importance of disturbance when considering the invasibility of habitats

12. References
Davis, Mark A., J. Philip Grime, and Ken Thompson. “Fluctuating resources in plant communities: A general theory of invasibility.” Journal of Ecology 88.3 (2000): Web.
Kercher, Suzanne M., Zedler, Joy B. “Multiple disturbances accelerate invasion of reed canary grass (Phalaris arundinacea L.) in a mesocosm study.” Oecologia Volume 138, Issue 3 (2004): Web.