Collaborative Research: Superinvaders: testing a general hypothesis of forest invasions by woody species across the Americas

Invasive plant species are a form of biological pollution that cost billions of dollars each year in lost crop and timber production, and they are one of the principal threats to native biodiversity. Effective management of invasive species requires that scientists understand how they compete successfully with native species. One of the least understood behaviors of invasive plants is that a single invasive species can dominate in many different types of environments. In particular, scientists have identified a group of ‘superinvaders’ that, counter to what is expected for native species, can grow very fast in sunlight but also tolerate heavy shade in the forest understory. Although there is good evidence that this behavior drives their increasing abundance in both temperate and tropical forests, scientists don’t understand how this occurs: why should invasive species play by different rules than native species in the same environment? One hypothesis is that invasive species have fewer pests than native species, and this advantage allows them to persist in stressful environments. In this project, ecologists will experimentally test this idea in many different types of forests to determine how this ‘superinvader’ behavior emerges. Moreover, by linking how plants simultaneously respond to pests and environmental stress, scientists will better understand how species coexist to foster native biodiversity. The project will train two US doctoral students, one postdoctoral scholar and numerous undergraduate students. The project will foster international collaboration, research partnerships and knowledge transfer across the Americas. This will benefit US scientists, doctoral student trainees and postdoctoral scholar. A new Research Experience for Undergraduates program at the University of South Carolina and a summer workshop in Puerto Rico will contribute to broadening participation by undergraduate students from groups under-represented in science and technology. The postdoctoral scholar will lead an effort to create a Forest Superinvader Network that will increase the scope of this project to the global level to facilitate international knowledge transfer and more effective forest and land management worldwide through better understanding of plant invasion mechanisms. The project involves two components. In the first, research teams will monitor the growth and survival of native and invasive tree saplings across lights gradients in 10 locations across the Americas, including temperate forests in Connecticut and South Carolina, tropical forests in Mexico, Costa Rica, and the Caribbean, and subtropical forests in southern Brazil. Using field measurements of metabolic activity of different tissues above- and belowground, researchers will test the hypothesis that lower energy costs in invaders, as a result of fewer pests, allows these invaders to circumvent functional tradeoffs typically associated with fast growth and shade tolerance. In a second component conducted in five locations, researchers will experimentally remove insects and fungal pathogens from native and invasive saplings to test whether shade tolerance is driven by pest loads. In both components, researchers will build and test integrative models of plant behavior that consider the energetic costs of seemingly disparate behaviors (e.g., resource capture versus defense) to further scientific understanding of critical linkages between plant functional ecology and population dynamics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.