Clonal integration facilitates Alternanthera philoxeroides invading to native plant populations.
Many exotic plant invader are clonal, and it is of great significance to understand the contribution of the clonal traits on their invasiveness. To reveal the contribution of the clonal integration and the division of labor on the invasiveness of this plant invader, we investigated the effects of the clonal integration (stolon connection) on the resource allocation, growth, physiology and competitive ability of the invasive Alternanthera philoxeroides clonal fragments under the competition by the different density of the native Ludwigia peploides plant populations. The results showed that native plant competition significantly reduced the final biomass, ramet number and the total stolon length of both the apical ramets and the whole fragments. Clonal integration greatly improved the growth performance and the competitive ability of the apical ramet of A. philoxeroides when suffering the competition by the native plant population, especially under high density competition. Clonal integration also greatly increased the final biomass of the whole fragment under high density competition. Moreover, the stolon connection allowed the division of labor within the clonal fragment under the competitive environment, with the basal ramets specializing in acquisition of belowground resources and the apical ramets specializing in acquisition of aboveground expansion. Therefore, It is concluded that the clonal integration can facilitate the invasion of A. philoxeroides into native plant populations.