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Aims Natural hybridization between invasive and native species, as a form of adaptive evolution, threatens biodiversity worldwide. However, the potential invasive mechanisms of hybrids remain essentially unexplored, especially insights from soil chemical properties and soil microbial communities. Methods In a field experiment, soil microbial community, potassium-solubilizing bacteria, phosphorus-solubilizing bacteria, enzyme activities, and light-saturated photosynthetic rate were measured in invasive Sphagneticola trilobata and its hybrid with native Sphagneticola calendulacea in 2 years. Important Findings In general, soil dissolved organic carbon and the biomass of phosphorus-solubilizing bacteria were significantly higher under the hybrid treatment than S. trilobata and S. calendulacea. However, there were no significant differences in acid phosphatase, total PLFAs, bacterial PLFAs, fungi PLFAs, cellulase, and urase in these treatments. The hybrids had significantly higher light-saturated photosynthetic rate, photosynthetic nitrogen-, phosphorus-, potassium- use efficiencies than the invasive S. trilobata, but no significant difference with S. calendulacea. The total biomass and root biomass of hybrids were higher than S. calendulacea. Our results indicate that the hybrids species have a higher invasive potential than S. calendulacea, which may aggravate the local extinction of S. calendulacea in the future.

Mikania micrantha is one of the top 100 worst invasive species that can cause serious damage to natural ecosystems and substantial economic losses. Here, we present its 1.79 Gb chromosome-scale reference genome. Half of the genome is composed of long terminal repeat retrotransposons, 80% of which have been derived from a significant expansion in the past one million years. We identify a whole genome duplication event and recent segmental duplications, which may be responsible for its rapid environmental adaptation. Additionally, we show that M. micrantha achieves higher photosynthetic capacity by CO2 absorption at night to supplement the carbon fixation during the day, as well as enhanced stem photosynthesis efficiency. Furthermore, the metabolites of M. micrantha can increase the availability of nitrogen by enriching the microbes that participate in nitrogen cycling pathways. These findings collectively provide insights into the rapid growth and invasive adaptation., Mikania micrantha is an extremely fast-growing invasive plant species that can cause serious damage to natural ecosystems. Here, the authors assemble its chromosome-scale reference genome and explore possible mechanisms that contribute to its rapid growth.

Seagrasses play an important role in coastal marine ecosystems, but they have been increasingly threatened by human activities. In recent years, seagrass communities have rapidly degenerated in the coastal marine ecosystems of China. To identify the reasons for the decline in seagrasses, the phytotoxic effects of trace metals (Cu, Cd and Zn) on the seagrass Thalassia hemprichii were investigated, and the environmental contents of the metals were analyzed where the seagrass grows. The results showed that leaf necrosis in T. hemprichii exposed to 0.01–0.1 mg L−1 of Cu2+ for 5 days was more serious than that in plants exposed to the same concentrations of Cd2+ and Zn2+. The chlorophyll content in T. hemprichii declined in a concentration-dependent manner after 5 days of exposure to Cu2+, Cd2+ and Zn2+. The evident reduction in ΔF/Fm’ in T. hemprichii leaves was observed at day 1 of exposure to 0.01–1.0 mg L−1 of Cu2+ and at day 3 of exposure to 0.1–1.0 mg L−1 of Cd2+. The antioxidant enzyme activities (SOD, POD and CAT) in T. hemprichii leaves exposed to the three metal ions also showed significant changes. In seawater from Xincun Bay (Hainan, China), where T. hemprichii grows, Cu had reached a concentration (i.e., 0.01 mg L−1) that could significantly reduce chlorophyll content and ΔF/Fm’ in T. hemprichii leaves. Our results indicate that Cu influences the deterioration of seagrasses in Xincun Bay.

Potassium is directly involved in plant cell turgor-driven cell elongation, this is important for promoting the expansion of invasive plants. Soil potassium-solubilizing microorganisms in some invaded ecosystems may promote plant invasion by increasing potassium availability. The aims of this study were to isolate and identify potassium-solubilizing bacteria and to evaluate their contribution to the solubilization of potassium from potassium-feldspar, and to the potassium uptake of Mikania micrantha. Potassium-solubilizing bacteria were isolated using solid Aleksandrov medium in abandoned orchards that have been highly invaded by M. micrantha for more than 10 years. Our results revealed that 18 strains of efficient bacteria were identified using liquid Aleksandrov medium. Among the isolates, the Burkholderia genus had the highest solubilizing ability (1.75 mg L−1). The results of the pot culture experiment showed that the plant biomass and potassium content of M. micrantha with potassium-solubilizing bacteria were higher than in the control without these bacteria. Incubation with potassium-solubilizing bacteria, especially GZ18, significantly increased the plant phosphorus content. More potassium was solubilized in treatments with potassium-solubilizing bacteria than in the control without bacteria. These results strongly suggest that potassium-solubilizing bacteria in the rhizosphere of M. micrantha could improve potassium solubilization and uptake, and contributed to their success as an invasive species.

Microbial-microfaunal interactions play important roles in nutrient release and plant nutrient acquisition. However, the extent of their effects is sensitive to plant species identity, particularly among invasive plants, and the difference in effects can change the proportional abundances of soil functional groups, and subsequently change plant-soil element contents. Although the effects of invasive plants on soil microorganisms have been a widespread focus of ecological research, interspecific interactions with fauna are rarely considered in studies of plant invasion. We explored the potential of soil nematodes to mediate microbial responses to an invasive plant (Mikania micrantha) and a native plant (Persicaria chinensis) in South China, where ecological niches are extremely sensitive to exotic species because of anthropogenic degradation of the native vegetation. Rhizosphere soil samples were collected from three different habitats highly invaded by M. micrantha, and the abundance and community composition of the nematode and microbial communities were examined. A microcosm experiment was also conducted to test whether nematode feeding significantly affected specific bacteria-mediated ecological processes, such as potassium release in the soil. The results of the correlation analysis, structural equation modeling and laboratory microcosm experiments consistently indicated that the abundance of bacterivores was positively correlated with bacterial biomass, including that of potassium-solubilizing bacteria. In microcosms, the most dominant bacterivore, Eucephalobus, significantly increased potassium release by stimulating the colonies and activity of potassium-solubilizing bacteria. Meanwhile, M. micrantha had higher potassium stocks in plant tissues, especially in the roots, than did P. chinensis. These findings clearly suggest that invasive plants may enhance microbial-microfaunal interactions that in turn stimulate nutrient release.