Brazilian peppertree is classified as one of the most damaging invasive plant species in Florida and Hawaii. Originally introduced as an ornamental from Brazil, this small tree effectively outcompetes native vegetation by forming dense monocultures and is very difficult to control through conventional means such as cutting and herbicide applications. This project is part of a long-term collaboration with researchers from the University of Florida (William Overholt, James Cuda, Veronica Manrique, Rodrigo Diaz) and the USDA ARS in Ft. Lauderdale, FL (Gregory Wheeler, Paul Pratt, John Geiger). The ultimate goal of our studies is to develop a safe, effective biological control program for this species and to determine why Brazilian peppertree is such a successful invader. We have used molecular markers to determine the introduction history of Brazilian peppertree into Florida, map the pattern of colonization within Florida, identify source regions in Brazil, and study how intraspecific hybridization may have facilitated the success of this species in Florida. Additionally, we are studying the taxonomy, population genetic structure, and host specificity of potential Brazilian peppertree biological control agents (thrips, psyllids, and moths).