Seedlings of the introduced invasive shrub Eugenia uniflora (Myrtaceae) outperform those of its native and introduced non-invasive congeners in Florida

Abstract

One particularly compelling explanation for the success of invasive species is the ability to outperform other species in characteristics affecting fitness. Past studies have compared native or introduced non-invasive species to their invasive counterparts, while a system incorporating both native and introduced non-invasive congeners provides an opportunity for multiple controls. We used such a system of Eugenia congeners in Florida to compare seedling performance. In order to determine if invasive Eugenia uniflora seedlings outperform those of its congeners, we sowed seeds in the field and a common garden and quantified seedling emergence, growth, and survival, as well as foliar damage by insect herbivores. We obtained similar results in the field and garden experiments. Although there were no differences in seedling emergence for E. uniflora seedlings when compared to some of its introduced congeners in certain years, emergence of E. uniflora seedlings was consistently high across years. However, emergence, growth, and survival rates of native species were consistently low. In addition, E. uniflora outperformed its introduced and native congeners in growth and survival traits in most comparisons, even when sustaining higher levels of herbivore damage by an introduced weevil, Myllocerus undatus Marshall. Our results support our predictions, indicating that invasive E. uniflora may possess a competitive advantage because its seedlings perform better than or equivalently to its congeners in all of the attributes quantified. Our study further suggests that measurements of such traits may be useful in determining the likelihood of invasion by newly introduced woody plant species.