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Submitted to: Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/30/2005 Publication Date: 10/14/2005 Citation: Blumenthal, D.M. 2005. Interrelated causes of plant invasion: resources increase enemy release. Science. 310:243-244. Interpretive Summary: Understanding why invasive species invade is essential to achieving long-term control. Two ideas have prominence in explaining plant invasion: release from natural enemies and increased resource availability. Here I suggest for the first time that these causes are not independent. Rather, enemy release may increase with increasing resource availability. When plants invade new continents, they leave many herbivores and pathogens behind. Species most regulated by enemies in their native range have the most potential for enemy release, and enemy regulation is strongest for high-resource species. High resource availability is associated with low defense investment, high nutritional value, high enemy damage, and consequently strong enemy regulation. Strong enemy release of high-resource species leads to several novel predictions. Anthropogenic increases in resource availability, ranging from small-scale disturbances to global climate change, will not just facilitate invasion, but facilitate invasion by exotic species in particular. Furthermore, both enemy release and resources will underlie many invasions, suggesting possible synergy between biological control and resource-based control methods. This hypothesis also explains observed tendencies of exotic plants to have high-resource traits, and to succeed in high-resource environments. Technical Abstract: Understanding why invasive species invade is essential to achieving long-term control. Two ideas have prominence in explaining plant invasion: release from natural enemies and increased resource availability. Here I suggest for the first time that these causes are not independent. Rather, enemy release may increase with increasing resource availability. When plants invade new continents, they leave many herbivores and pathogens behind. Species most regulated by enemies in their native range have the most potential for enemy release, and enemy regulation is strongest for high-resource species. High resource availability is associated with low defense investment, high nutritional value, high enemy damage, and consequently strong enemy regulation. Strong enemy release of high-resource species leads to several novel predictions. Anthropogenic increases in resource availability, ranging from small-scale disturbances to global climate change, will not just facilitate invasion, but facilitate invasion by exotic species in particular. Furthermore, both enemy release and resources will underlie many invasions, suggesting possible synergy between biological control and resource-based control methods. This hypothesis also explains observed tendencies of exotic plants to have high-resource traits, and to succeed in high-resource environments. |
