HYBRID VIGOR FOR THE INVASIVE EXOTIC BRAZILIAN PEPPERTREE (SCHINUS TEREBINTHIFOLIUS RADDI., ANACARDIACEAE) IN FLORIDA

How can successful invaders overcome reduced genetic variation via small founder population sizes to persist, thrive, and successfully adapt to a new set of environmental conditions? An expanding body of literature posits hybridization, both inter- and intraspecific, as a driver of the evolution of invasiveness via genetic processes. We studied Brazilian peppertree (Schinus terebinthifolius), a tree species native to South America that is a successful invader throughout Florida. The tree was introduced separately to the east and west coasts of Florida more than 100 years ago from genetically distinct source populations. We conducted a common garden experiment to compare the early life-stage performance of hybrids versus their progenitors. We hypothesized that hybrids would outperform their progenitors due to the positive genetic effects of intraspecific hybridization (i.e., hybrid vigor). Hybrid seeds germinated at higher rates than eastern seeds. Over the 8-mo experiment, a greater proportion of hybrid seedlings survived than did western seedlings, and hybrids attained greater biomass than the western types. The cumulative hybrid advantage of both seed germination and seedling survival led to the establishment of nearly 45% more hybrid seedlings versus either progenitor. Documenting fitness advantages for hybrids over their progenitors is a requisite finding to consider hybridization as a factor in the success of invasive species.