By: Megan Murphy, Sarah Brodeur, Lauren Bettino,
Jenna Del Buono, and Keith Green

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

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

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

● Invasions are influenced by three general factors:
1. Propagule pressure
2. Invasive species characteristics
3. 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

●
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

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

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

n=32 n=11

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

● Hypothesis IS well supported
● Bias/point of error: different number of articles reviewed for each taxonomic group o Terrestrial plants support hypothesis 71% of the time o Aquatic plants support hypothesis 83% of the time o Pathogens and insects support hypothesis 100% of the time o 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

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): 528-34. 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): 455-64. Web.