SYMP 7

Beyond Invasional Meltdown: Implications and Impacts of Co-Occurring Invasive Species and Assessing Future Research Needs

A hallmark of the Anthropocene is human-driven species relocation, which is causing notable population, community, and ecosystem impacts. This session critically expands invasion biology research by moving beyond single species approaches to evaluate the impacts and implications of multiple, co-occurring invasive species. Today, few ecosystems remain uninvaded by nonnative species and almost all ecosystems contain multiple coexisting invasive species. However, to date, most research has focused on single invaders, leaving a wide gap in our knowledge of how multiple invaders will interact to affect ecosystems. The proposed session will synthesize the current research on co-occurring nonnative plant invaders and will use this knowledge to generate new ideas and approaches to guide the next generation of invasion research. We bring together leading ecological experts who address a range of questions concerning co-occurring invaders across a diverse set of ecosystems and species. Their work encompasses theoretical and experimental studies that demonstrate the various impacts of co-occurring invaders. Importantly, this session will also use insights from these syntheses to develop recommendations for how best to manage ecosystems dominated by suites of invaders. We will begin with (1) a synthesis and overview of the main hypothesis—invasional meltdown—that discusses potential ramifications of co-occurring invaders and has set the stage for most co-occurring invader research. Next, we will present (2) a review of current knowledge of the impacts of co-occurring invaders from a suite of long- and short-term experimental studies, as well as a newly developed approach for quantifying invader impacts in the context of a multiple-invasion scenario. This will lead to (3) a discussion of invasive plant management and the likelihood of “secondary invasions” depending on the type of control method and ecosystem composition. A final conclusive presentation will (4) offer insight into future research directions and gaps in knowledge of co-occurring invaders.