Forecasting ecological responses to climate change, invasion, and their interaction must rely on understanding underlying mechanisms. However, such forecasts require extrapolation into new locations and environments. We linked demography and environment using experimental biogeography to forecast invasive and native species' potential ranges under present and future climate in New England, United States to overcome issues of extrapolation in novel environments. We studied two potentially nonequilibrium invasive plants' distributions, Alliaria petiolata (garlic mustard) and Berberis thunbergii (Japanese barberry), each paired with their native ecological analogs to better understand demographic drivers of invasions. Our models predict that climate change will considerably reduce establishment of a currently prolific invader (A. petiolata) throughout New England driven by poor demographic performance in warmer climates. In contrast, invasion of B. thunbergii will be facilitated because of higher growth and germination in warmer climates, with higher likelihood to establish farther north and in closed canopy habitats in the south. Invasion success is in high fecundity for both invasive species and demographic compensation for A. petiolata relative to native analogs. For A. petiolata, simulations suggest that eradication efforts would require unrealistic efficiency; hence, management should focus on inhibiting spread into colder, currently unoccupied areas, understanding source-sink dynamics, and understanding community dynamics should A. petiolata (which is allelopathic) decline. Our results-based on considerable differences with correlative occurrence models typically used for such biogeographic forecasts-suggest the urgency of incorporating mechanism into range forecasting and invasion management to understand how climate change may alter current invasion patterns.demography | integral projection model | garlic mustard | Japanese barberry | species distribution model I nvasions and climate change are two of the primary factors that alter ecological systems. Forecasting ecological responses to these dynamic, potentially no-analog scenarios requires biologists to understand the fundamental processes that regulate change. The interaction of climate change and invasion remains a mystery, although it has been argued that climate change may foster invasions in many cases, whereas inhibition is less likely (1, 2). Studies have focused on such positive interactions (3), because they are readily observed; it is difficult to recognize when climate change has mitigated an invasion simply because there may not be an invasion to study. Only with a mechanistic understanding of how climate regulates life history transitions to mitigate or accelerate invasions can we improve the efficiency of management plans.Links between global change and invasion are complex and idiosyncratic, although in general, climate change, land use change, and increased resource availability seem to favor invasive species over natives (examples are rev...

response to the global threat oj invasive alien species, there has been a proliferation of volunteer-based monitoring programs. The valuable data sets collected through these programs facilitate large-scale, baseline population monitoring. The Invasive Plant Atlas of New England, created in 2001, was the first such regional database and is the only one in which both presence and true absence data have been collected. Building on the success of volunteer atlas projects for other taxa, the Web-based network uses trained volunteers, along with experts, to collect distribution data and detailed environmental information. The incorporation of true absence data allows for the building of robust statistical models, which contributes significantly to the invasive species literature. This collaborative database allows citizen science data to be used by the general public and as a data source for researchers and policymakers. As a template for other invasive plant projects, we highlight the need for more collaborative efforts in invasion ecology.

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