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United States Department of Agriculture

Agricultural Research Service

Research Project: SEMIARID RANGELAND ECOSYSTEMS: THE CONSERVATION-PRODUCTION INTERFACE

Location: Rangeland Resources Research

Title: Synergy Between Pathogen Release and Resource Availability in Plant Invasion

Authors
item Blumenthal, Dana
item Mitchell, Charles - UNIV OF N. CAROLINA
item Pysek, Petr - ACAD. OF SCI., CZECH REPU
item Jarosik, Vojtech - CHARLES UNIV., CZECH REP

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2009
Publication Date: April 27, 2009
Repository URL: http://parking.nal.usda.gov/shortterm/21087_14.BlumenthalMitchellPysekJarosik2009-PNAS-Synergyinplantinvasions.pdf
Citation: Blumenthal, D.M., Mitchell, C.E., Pysek, P., Jarosik, V. 2009. Synergy Between Pathogen Release and Resource Availability in Plant Invasion. Proceedings of the National Academy of Sciences 106(19):7899-7904.

Interpretive Summary: Why do some exotic plant species become invasive? Two common hypotheses, increased availability of plant resources (such as light, water and nitrogen) and loss of natural enemies following introduction to a new continent (enemy release), may more effectively explain invasion if they favor the same species. We tested this possibility for the first time by examining how resource adaptations influence the number of pathogen species infecting 243 European plant species in both their native European range, and their introduced range in the in the United States. Plants adapted to wet environments hosted more fungal species than plants adapted to dry environments, and plants adapted to nitrogen-rich environments hosted more viruses than plants from nitrogen-poor environments. Plant species previously classified as competitors (adapted to high resource availability) hosted more than four times as many species of fungi and viruses in Europe as did stress tolerators (adapted to low resource availability). Patterns of enemy release mirrored those of pathogen richness: competitors were released from many pathogen species, while stress tolerators and species from dry and nitrogen-poor environments were released from relatively few pathogen species. These results suggest that enemy release contributes most to invasion by fast-growing species in resource-rich environments. Consequently, enemy release and increases in resource availability may co-occur, and act together to cause invasion.

Technical Abstract: Why do some exotic plant species become invasive? Two common hypotheses, increased resource availability and enemy release, may more effectively explain invasion if they favor the same species, and therefore act in concert. This would be expected if plant species adapted to high levels of available resources in their native range are particularly susceptible to enemies, and therefore benefit most from a paucity of enemies in their new range. We tested this possibility for the first time by examining how resource adaptations influence pathogen richness and release among 243 European plant species naturalized in the United States. Plants adapted to mesic environments hosted more fungi than plants adapted to xeric environments, and plants adapted to nitrogen-rich environments hosted more viruses than plants from nitrogen-poor environments. Plant species previously classified as competitors (adapted to high resource availability) hosted more than four times as many species of fungi and viruses in Europe as did stress tolerators (adapted to low resource availability). Patterns of enemy release mirrored those of pathogen richness: competitors were released from many pathogen species, while stress tolerators and species from xeric and nitrogen-poor environments were released from relatively few pathogen species. These results suggest that enemy release contributes most to invasion by fast-growing species in resource-rich environments. Consequently, enemy release and increases in resource availability may co-occur, and act synergistically to cause invasion. Furthermore, anthropogenic increases resource availability may indirectly increase enemy release (by selecting for strongly-released fast-growing species), and therefore favor exotic over native species.

Last Modified: 9/23/2014
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