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Fluctuating Resources: A General Theory of Invasibility
By: Megan Murphy, Sarah Brodeur, Lauren Bettino, Jenna Del Buono, and Keith Green
Original Paper
Fluctuating resources in plant communities: a general theory of invasibilityBy:Mark A. Davis, J. Philip Grime and Ken ThompsonPublished In Journal of Ecology, 2000
The Theory
Communities are more prone to invasion as a direct result of the presence of excess unused resources.
The Theory● 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 supply2. A decline in resource uptake3. A combination of both
Background
● Invasions are influenced by three general factors:1. Propagule pressure2. Invasive species characteristics3. 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
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
Background
● Designed experiment: controlled grassland plotso Tested: effects of varying disturbance and
fertility gradients on invasions● Results:
o Increased disturbance = increased invasions
o Increased fertilizer = increased invasions
Literature Review / Methods
● 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
Kercher & Zedler: Phalaris arundinacea L.
● Designed experiment: controlled mesocosmso Tested: effects of light availability, nutrients
levels, flooding (disturbance) on invasions● Results:
o Increased nutrients = increased P. arundinaceao Increased light = increased P. arundinaceao Most rapid invasion during max levels of both
nutrients and light at once
○ Increased flooding = increased P. arundinacea
P. arundinacea; Reed canary grass
Discussion● Hypothesis IS well supported● Bias/point of error: different number of articles reviewed for each
taxonomic groupo Terrestrial plants support hypothesis 71% of the timeo Aquatic plants support hypothesis 83% of the timeo Pathogens and insects support hypothesis 100% of the timeo 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
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): 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.