Functional trait-based potential invasiveness of exotic submerged macrophytes and their effects on sediment bacterial community

Functional traits of exotic species play an important role in their invasive process by enhancing their performance and promoting them as a potentially malignant invasive species. However, the interrelationship between functional traits and invasion capacity of exotic aquatic species is still not clear. Here, we selected two exotic aquatic species Egeria densa Planch. and Myriophyllum aquaticum (Vell.) Verdc. and two related native species Hydrilla verticillata (L. f.) Royle and Myriophyllum spicatum L. in China to reveal the potential invasiveness of exotic submerged macrophytes based on functional traits and their effects on sediment bacterial community. Our results showed that there was no significant competition between exotic species and related native species. Many functional traits of related native species H. verticillata performed significantly better than exotic species E. densa beside leaf area. Related native species M. spicatum also had obvious advantages in important functional traits such as relative growth rate and nutrient concentrations. The belowground part of two exotic species had significant effects on sediment bacterial community. Due to developed roots and their radial oxygen loss of exotic species E. densa and M. aquaticum, the diversity of sediment bacterial community positively correlated with exotic species ratio in treatment. Some dominant sediment bacteria, such as Streptomyces, might accelerate the invasion of exotic species through feedback effects. In general, compared with related native species, the competitive ability and functional traits of exotic plants did not show significant invasion ability. However, positive interaction with sediment bacteria and moderate interspecific relationships may promote the invasion of exotic submerged macrophyte species. Our results provide a theoretical basis for risk assessment and effective management of exotic aquatic plants.