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 invasibility By: Mark A. Davis, J. Philip Grime and Ken Thompson Published 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: A pulse in resource supply A decline in resource uptake A combination of both

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

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 plots Tested: effects of varying disturbance and fertility gradients on invasions Results: Increased disturbance = increased invasions Increased fertilizer = increased invasions

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

Does the literature support the fluctuating resources hypothesis?

Taxonomic groups that follow the fluctuating resources hypothesis

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

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

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.