Reciprocal interactions of an invasive weed, Cirsium arvense, and its natural enemies

Non-native plants are a serious environmental and economic problem in southern Canada. Many of these plants initially gain an advantage by escaping natural enemies (insects and pathogens) unable to disperse with them to North America. In attempts to minimize the spread of non-native species, native-range enemies sometimes are deliberately released into the invaded range as a method of biological control. As well, invaders may acquire native enemies that limit their success. We are investigating factors influencing the impacts of enemies including insects and pathogens on the invasive non-native Canada thistle (Cirsium arvense). Specifically, we are investigating whether damage to C. arvense declines with distance from existing thistle populations, and whether this damage has a significant impact on performance. Experimental populations are being used to measure the impact of herbivorous insects and pathogens on growth and reproduction, and patterns of pathogen and insect attack will be measured in natural populations.

Principal Investigator: Peter M. Kotanen

Researchers: Krystal Nunes, Gurpreet Chandi, Ariana Longley, Neil Oliveira

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