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Invasive plants are able to establish persistent monocultures and outcompete native plants. The most popular hypothesis for why this is the enemy release hypothesis (ERH, Keane and Crawley, 2002). Enemy release proposes that specific pathogens and predators that limit the native range are absent in the exotic range. A central question of this hypothesis is how long does it takes for enemies to catch up? This may seem like a trivial question, but its answer is elusive. This question is why MPG Ranch has joined the Terrestrial Invasive Plant Species (TIPS) Network Project. The goal of this large-scale collaborative research initiative is to coordinate citizen collection of eight focal invasive exotic plants that are spreading across North America. If local enemies attack or catch up with exotic plants, older invasions should harbor more enemies and be less competitive against native plants. We will focus on enemies that attack plant roots. Our inspections will quantify the abundance of root lesions caused by pathogens, mesofauna, and insect herbivores. Please visit the website to learn more about the project, and how to participate.

Please visit the website to learn more about the project, and how to participate.


Keane RM and Crawley MJ (2002) Exotic plant invasions and the enemy release hypothesis. Trends in Ecology and Evolution 4: 164-170

About the Author

Ylva Lekberg

Ylva graduated from the Swedish University of Agricultural Sciences with a M.Sc. in Biology and Horticulture in 1996 and a Ph.D. in Ecology from Penn State University in 2004. She received the Alumni Association Dissertation Award for her work in agroecology and subsistence farming in Sub-Saharan Africa. Post-doctoral positions at Montana State University and later at Copenhagen University as a Marie Curie Fellow allowed her to explore the role of arbuscular mycorrhiza, a root-fungus symbiosis, for geothermal plants in Yellowstone National Park and coastal grasslands in Denmark. Her research has been published in international journals such as Nature Communications, Ecology Letters, and New Phytologist.

Ylva joined MPG Ranch in 2010. Since then, she has explored how invasive plants common to western Montana, including spotted knapweed (Centaurea stoebe), leafy spurge (Euphorbia esula) and cheatgrass (Bromus tectorum), influence soil microbial community composition and function, and how this in turn may affect invasive success. A lot of her research also focuses on the AM symbiosis in terms of community ecology and physiology. A current project addresses how exchange ratios in this symbiosis may differ among co-occurring plants and depend on soil nutrient availabilities. She uses surveys, field and greenhouse experiments, and literature approaches such as meta-analyses to address questions. To learn more about research and publications from Ylva and her group, see CV below and the Soils, Plants and Invasion section.

In addition to her work at MPG Ranch, Ylva is an adjunct professor at University of Montana at the Department of Ecosystem and Conservation Sciences.