Many invasive plants have enhanced mutualistic arbuscular mycorrhizal (AM) fungal associations, however, mechanisms underlying differences in AM fungal associations between introduced and native populations of invasive plants have not been explored. Here we test the hypothesis that variation in root exudate chemicals in invasive populations affects AM fungal colonization and then impacts plant performance. We examined flavonoids (quercetin and quercitrin) in root exudates of native and introduced populations of the invasive plant Triadica sebifera and tested their effects on AM fungi and plant performance. We found that plants from introduced populations had higher concentrations of quercetin in root exudates, greater AM fungal colonization and higher biomass. Applying root exudates more strongly increased AM fungal colonization of target plants and AM fungal spore germination when exudate donors were from introduced populations. The role of root exudate chemicals was further confirmed by decreased AM fungal colonization when activated charcoal was added into soil. Moreover, addition of quercetin into soil increased AM fungal colonization, indicating quercetin might be a key chemical signal stimulating AM fungal associations. Together these results suggest genetic differences in root exudate flavonoids play an important role in enhancing AM fungal associations and invasive plants’ performance, thus considering root exudate chemicals is critical to unveiling mechanisms governing shifting plant-soil microbe interactions during plant invasions.

Many alien aquatic plants are deliberately introduced because they have economic, ornamental, or environmental values; however, they may also negatively affect aquatic ecosystems, by blocking rivers, restricting aquatic animals and plants by decreasing dissolved oxygen, and reducing native biodiversity. These positive and/or negative ecological effects may be enhanced under global change. Here, we examine the impacts of global change on aquatic alien plant introduction and/or invasions by reviewing their introduction pathways, distributions, and ecological effects. We focus on how climate change, aquatic environmental pollution, and China’s rapid economic growth in recent decades affect their uses and invasiveness in China. Among 55 species of alien aquatic plants in China, 10 species are invasive, such as Eichhornia crassipes, Alternanthera philoxeroides, and Pistia stratiotes. Most of these invaders were intentionally introduced and dispersed across the country but are now widely distributed and invasive. Under climate warming, many species have expanded their distributions to areas where it was originally too cold for their survival. Thus, these species are (and will be) considered to be beneficial plants in aquaculture and for the restoration of aquatic ecosystems (for water purification) across larger areas. However, for potential invasive species, climate warming is (and will be) increasing their invasion risk in more areas. In addition, nitrogen deposition and phosphorus inputs may also alter the status of some alien species. Furthermore, climate warming has shifted the interactions between alien aquatic plants and herbivores, thus impacting their future spreads. Under climate change, more precipitation in North China and more frequent flooding in South China will increase the uncertainties of ecological effects of alien aquatic plants in these regions. We also predict that, under the continuing booming economy in China, more and more alien aquatic plants will be used for aquatic landscaping and water purification. In conclusion, our study indicates that both human activities under rapid economic growth and climate change can either increase the potential uses of alien aquatic plants or make the aquatic invaders worse in China and other areas in the world. These findings are critical for future risk assessment of aquatic plant introduction and aquatic ecosystem restoration.

Rapid global environmental changes could exacerbate the impacts of invasive plants on indigenous plant diversity, especially for freshwater ecosystems characterized by relatively simple plant community structures with low bioresistance. However, the abiotic and biotic determinants of plant diversity in aquatic invaded habitats remain unclear. In this study, we measured four α-species diversity indices (the Patrick richness index, Shannon–Wiener diversity index, Simpson diversity index, and Pielou evenness index) in aquatic plant communities invaded by Eichhornia crassipes in southern China. We also recorded eight environmental parameters of these communities (longitude, latitude, elevation, dissolved oxygen, water conductivity, nitrate nitrogen, temperature, and precipitation), together with nine biotic traits of E. crassipes [abundance, invasion cover, height, total carbon (C) content of the leaves and stems, total nitrogen (N) content of the leaves and stems, and the C:N ratio of leaves and stems]. We then used regression analysis and redundancy analysis (RDA) to determine the dominant factors related to plant diversity. We found that the environment significantly affected E. crassipes abundance, height, coverage, stem carbon, and tissue nitrogen, while the leaf C:N stoichiometric ratio was relatively stable. Increasing longitude significantly increased plant diversity, while elevated dissolved oxygen and precipitation slightly improved plant diversity, but increased elevation caused negative effects. E. crassipes invasion significantly decreased all four diversity indices. Increases in E. crassipes coverage and leaf C:N strongly decreased plant diversity, and increased abundance slightly decreased diversity. Our study indicates that both the changing water environment and the properties of the aquatic invasive plants could have significant impacts on plant diversity. Thus, more attention should be paid to aquatic invasion assessment in lower longitudinal regions with lower native hydrophyte diversity.

Invasive plants may change their seed traits to adapt to the environment and facilitate their performance. Studies on variation in seed traits among populations of an invader along latitudes/longitudes may assist in revealing how invasive plants cope with variable climates. In this study, we collected seeds of 26 populations of the global invasive plant Ambrosia artemisiifolia along ranges spanning 23° latitudes and 20° longitudes that are highly correlated in its invasive range in China. We measured over 20 seed traits, including seed morphology, phytohormone, nutrients, and germination, and investigated how the climate along the latitudes affects those traits. We found that germination time was significantly delayed with increasing latitude and longitude, while the reversed patterns were true for the germination rate. From low to high latitude, seed size, abscisic acid, and fatty acid were increased, likely affecting seed germination. Our analysis further demonstrated that temperature is the dominant driver of the variability in seed traits and germination. Germination rates of larger seeds in cold ranges were lower, while smaller seeds from warm ranges germinated faster, likely indicating adaptive strategies of the invasive plant in seed trait functional ecology. Together, our findings provide new insights into understanding the seed adaptation strategies during the invasion process and the underlying physiological and biochemical mechanisms involved.