Differences In Phenotypic Plasticity In Response To Soil Moisture Between Invasive And Their Phylogenetically Related Native Plants

Phenotypic plasticity has been considered as one of the main mechanisms for plant invasion under environmental fluctuations, Drought is the most common environmental stress plants experience. The purpose of this study is to explore the relationship between phenotypic plasticity and invasiveness. To fulfill this purpose, we compared the phenotypic plasticity of five invasive species with that of their native congeners under four different moisture conditions, in order to explore the relationship between phenotypic plasticity and invasiveness.The study explored the differences of phenotypic plasticity for both functional traits and fitness traits between the invasiveand their native congenersacross four water levels. The functional traits includedtotal biomass and relative growth rate and the functional traits included morphological traits, biomass allocation traits and physiological traits. The results showed that species varied in their water requirements. Bidens frondosa had a larger water consumption demand than other four species. However, Melilolus albus could survive under very low water level. In moist condition, the fitness traits of Solanum rostratum and Xanthium italicum showed more plastic than their native congeners which could improve their fitness under sufficient water supplly. In dry condition,xanthium italicum. Ambrosia trifida and Bidens frondosaa had lower fitness plasticity than the native congeners which could ensure less fitness fluctuation for the invasive under drought sress. The role of phenotypic plasticity to Melilolus albuswas insignificant, possibly because its higher supporting organs biomass fraction, water-use efficiency and leaf water potential could contribute to its higher total biomass than the native congener.Only the adaptive plasticity could contribute to the plant fitness. The adaptive significance of plant trait plasticity is species specific, and also varies with conditions specific. Phenotypic plasticity of a plant trait and the identity of the trait have different influence on the invasiveness of exotic species. Trait identity played an important role in invasiveness of M.albus,whilephenotypic plasticity contributed to invasiveness of other four invasive species.