Invasion of Spartina alterniflora in China is greatly facilitated by increased growth and clonality: a comparative study of native and introduced populations

Different mechanisms have been proposed to explain invasion success of alien species, among which genetic differentiation and phenotypic plasticity are extensively studied. In order to explore whether the invasion of Spartina alterniflora is facilitated by enhanced phenotypes or trait plasticity, we conducted a common garden experiment on this clonal invasive plant, in which three native populations (from the US) and eight introduced populations (from China) were included and grown at two water levels. We measured their plant traits related to growth, reproductive phenology, reproductive output, and their plasticity in response to water availability. No difference in plant height was observed between native and introduced populations of S. alterniflora, but introduced populations had greater total biomass than the native ones at high water level. Reproductive performances facilitating invasion success were also found for introduced populations, indicated by the advanced initiation of phenological events, greater total number of ramets, and more investment of total biomass in rhizomes versus stalk and leaf in both water treatments. Finally, a non-significant difference in inflorescence biomass for flowering individuals and phenotypic plasticity of most measured traits was observed between native and introduced populations. In conclusion, enhanced growth and asexual reproduction make greater contributions to the invasion success of S. alterniflora in China.