The role of phenotypic plasticity and rapid adaptation in determining invasion success of Plantago virginica.
Nitrogen (N) enrichment may facilitate plant invasion because exotic plant species usually benefit more from high N availability and possess competitive advantages over indigenous species. Two non-exclusive mechanisms, phenotypic plasticity and rapid adaptation, have often been used to explain the colonization and range expansion of invasive plants in novel habitats, but whether they are still applicable under altered environmental conditions such as N addition remains unclear. Here, we focused on a weedy plant, Plantago virginica, which is native to North America that invaded China. We conducted a greenhouse experiment to compare the differences in phenotypic traits (e.g., biomass, leaf traits and reproductive output) and plasticity between multiple native and invasive populations subjected to high and low nutrient availability. We found that the invasive populations differentiated from native ones for a suite of traits, suggesting that rapid adaptation may have occurred in the invasive species. In particular, plants of invasive populations were larger and produced significantly more seeds per inflorescence and individual than their native counterparts. The traits measured in both invasive and native populations exhibited a large degree of plasticity in response to altered N supply, indicating a "master-of some" superiority of P. virginica. Meanwhile, the leaf area and belowground biomass of invasive populations at vegetative stage had a higher degree of plasticity than those of the native populations. Our results suggest that both phenotypic plasticity and rapid adaptation may jointly explain the advantages of invasive plants in N-rich environments, thereby increasing the risk of biological invasions under N deposition.