Post-establishment evolution of nonnative plant species in New England mainland and island habitats
Whereas a number of studies have demonstrated the tendency of nonnative plant populations to evolve rapidly following establishment, the habitat characteristics that drive evolution are poorly understood. The recently proposed Evolution of Reduced Competitive Ability (ERCA) hypothesis suggests that post-establishment evolution in some nonnative plant populations may be driven by the intensity of plant competition in the invaded habitat. Specifically, the ERCA hypothesis predicts that if the intensity of plant competition in the invaded habitat is low, invading plant populations may evolve a modified energetic tradeoff in which vegetative growth is decreased while reproductive effort and/or tolerance to herbivory are increased. My dissertation research has provided the first test of this hypothesis. I first demonstrated that the amount of vascular plant competition is lower in New England’s nearshore island habitats than in nearby mainland habitats. I then hypothesized, following the ERCA hypothesis, that island populations of nonnative plants should demonstrate decreased vegetative growth but increased reproductive effort and herbivore tolerance relative to mainland populations. I utilized three nonnative plant species commonly found along the New England coast (Lythrum salicaria , Solanum dulcamara, and Vincetoxicum nigrum ) to test these hypotheses using a variety of methods. I conducted a neighbor-removal field study in which I analyzed the response of mainland and island individuals to the removal of their competing neighbors. I also conducted a two-year common garden analysis in which I germinated seeds collected from 10 mainland and 10 island populations of each species and quantified evolved differences in growth, reproductive effort, and herbivore tolerance among populations. I then conducted an amplified fragment length polymorphism (AFLP) genetic analysis to quantify genetic variability among and within these populations. The collective results of these experiments suggest that localized adaptation has likely occurred in these three species following their respective introductions. In most of our experiments, the ERCA hypothesis accurately predicted evolved changes in growth, reproduction, and herbivore tolerance in each species. This research provides the first support for the ERCA hypothesis and enhances our understanding of the interaction between invading plant populations and their host environments. This information will contribute to the incorporation of evolutionary potential into regionally specific weed risk assessments (WRA) and predictive management schemes.
Genetics|Environmental science|Plant biology
Joshua P Atwood,
"Post-establishment evolution of nonnative plant species in New England mainland and island habitats"
Dissertations and Master's Theses (Campus Access).