Climatic conditions can limit the spread of an invasive species, but whether the species can expand its range or not may be influenced by its evolutionary potential. Here we determine how genotypes sampled from an invasive grass in its native and invasive range compare in terms of both life-history traits and evolutionary potential when grown along a climatic gradient. Phalaris arundinacea is a cool season grass that becomes invasive in cool wet areas. We collected genotypes from the center and the range margin of the North American invasive range (Vermont and North Carolina) and the native European range (Czech Republic and France) and established common gardens along a climatic gradient in the invasive range (Vermont) and southernmost (North Carolina).

Results/Conclusions  

In general, invasive genotypes had consistently greater stem height, tiller number and biomass than native genotypes; however this result was only statistically significant for the North Carolina site. In North Carolina, invasive genotypes had 31% greater tiller production and 42% greater biomass production than native genotypes. Plastic variance, which can be thought of as the range of responses a genotype exhibits under changing environmental conditions, was more than double that for invasive genotypes for several fitness traits (tiller number, aboveground biomass, belowground biomass and total biomass). Invasive genotypes also had significantly greater heritability at both sites for the traits of total biomass, above ground biomass, leaf number and stem height. Interestingly, invasive genotypes in North Carolina (range margin) had significantly greater heritability than invasive genotypes in Vermont (central range) for stem height, leaf number, belowground biomass and total biomass (all p<0.0001). Thus, we show that marginal populations of P.arundinacea may have greater evolutionary potential and therefore greater ability to adapt to changing environments. Our work suggests that invasive genotypes have more aggressive growth characteristics and greater evolutionary potential than native genotypes which may facilitate future spread.