Biological invasions present one of the greatest threats to native ecosystems and one of the greatest challenges for natural resource managers. Our goal is to advance knowledge of invasion ecology, invader impacts, and invasive species control tools in order to improve management of invasive species. We welcome your feedback to help us achieve this goal.
Effective management of invasive species requires the integration of community ecology theory and invasion biology in the context of a resource management framework. We have spent several years developing such a framework to guide our research program on the ecology and management of invasive species.
Community Ecology of Native Grassland Ecosystems
To understand how exotic species impact native ecosystems, we have to first understand how these systems function. This collaborative study with Dr. John Maron of the University of Montana examines how top-down (predation and herbivory) and bottom-up factors affect plant community composition of native grassland ecosystems in one of the largest experimental manipulations of its kind.
That exotic plants radically transform vegetation communities is readily apparent. Yet such impacts have rarely been quantified. To determine which native species are most at risk and evaluate the future trajectory of invaded systems, it is necessary to first understand the specific impacts of invaders on native plant communities. This study documents that not all native plants are equally affected by invasion of the exotic forb spotted knapweed, and projects the trajectory of communities as invasion proceeds.
The transformation of native plant communities by weed invasion has important implications for wildlife, but little is known about which wildlife species may be affected and how. Knowledge of the processes by which weeds impact wildlife populations is necessary to predict weed impacts over a range of species and devise effective management measures. Our research elucidates these processes by illustrating that the exotic plant, spotted knapweed impacts songbirds by eroding native food chains.
Because plants are generally perceived as food for animals, exotic plant invasions are expected to impact animals by affecting their food resources. However, plants also provide structure for animals, and plant architecture can strongly affect predator abundance and hunting behavior. We show how architectural changes in plant communities caused by weed invasion can increase densities of native predators and alter their behavior in ways that render them more lethal to their prey.
Classical biological control involves the intentional introduction of exotic invertebrates for suppression of exotic weeds. Biological control is one of the few tools proven effective at controlling widespread invasive plants. However, because biological control agents are themselves exotic organisms, great care must be taken to ensure they do not become pests in their own right. Our research establishes the importance of selecting agents that effectively control the target weed in order to minimize the risk of complex side effects.
Weed management in natural areas often focus on suppressing undesirable species in order to lessen the severity of their impacts. However, weed control tools have side effects that must be weighed against their beneficial effects to assure that management action is effective. Our research evaluates the benefits and side effects of suppressing weeds with broadleaf herbicide at differing stages of invasion and identifies ways to improve efficacy of this tool.
Why some exotic species are able to function as strong invaders is largely unknown. Through a common garden experiment, we examine the interaction of three forces potentially limiting the success of these invaders: biocontrol agents acting as natural enemies, drought conditions associated with climate change, and competition with other plant species. Understanding the factors limiting the success of strong invaders will improve the efficacy of weed management efforts.
Bird Song as an Indicator of Habitat Quality
Within many songbird species, each individual male has his own uniquely identifiable song. Local dialects develop as young males adopt songs that emulate established neighbors. Our research shows that factors such as exotic plant invasions that impact habitat quality can increase turnover rates of songbirds and disrupt local song dialects. Bird songs may provide a rapid means of assessing habitat quality for songbird populations.