Exploring how nitrogen deposition alters the competitive interactions between invasive plants and native plants is critical for predicting the invasion trends of invasive plants and for formulating their control strategies. In this study, the invasive plant Solanum rostratum and its native congener S. nigrum were selected as research subjects, and three different nitrogen (N) concentration treatments (N1: 50 mg·kg⁻¹, N2: 100 mg·kg⁻¹, N3: 150 mg·kg⁻¹) were set up to compare the two species in terms of growth and development, leaf nutrient utilization strategies, stress tolerance, and rhizosphere microbial community differences under competitive conditions. The results showed that the biomass of S. rostratum was 1.4 to 2.3 times that of S. nigrum; the former had a lower root–shoot ratio and a larger crown width, enabling it to seize more living space and light resources. Across all nitrogen treatments, the net photosynthetic rate of S. rostratum leaves was significantly higher than that of S. nigrum, reflecting a stronger carbon sequestration capacity. With the increase in soil nitrogen concentration, the malondialdehyde content in S. rostratum leaves showed a decreasing trend; meanwhile, its leaf soluble sugar and catalase contents were 3.5 to 4.3 times and 1.5 to 2.5 times those of S. nigrum, respectively, indicating a lower oxidative stress level and higher stress tolerance in S. rostratum. The leaf C/P and C/N ratios of S. rostratum increased with the rise in soil N, demonstrating a higher nutrient use efficiency, while the decrease in leaf phosphorus (P) content might be attributed to the element dilution effect caused by the rapid plant growth. In addition, the diversity and stability of the rhizosphere microbial community of S. rostratum gradually increased with increasing soil N and were significantly higher than those of S. nigrum. The rhizosphere-recruited microbes of the genera Comamonas and Chryseobacterium may help promote its root nutrient absorption and thus enhance its competitive ability. Collectively, our findings reveal that under exogenous N application, S. rostratum gains a significant growth advantage over S. nigrum, which is attributed to its stronger capacities for carbon assimilation and spatial resource acquisition, a nutrient strategy characterized by low acquisition and high utilization, as well as a stable and diverse rhizosphere microbial community.

Plant communities may be co-invaded by invasive plants, sometimes even by congeneric invasive plants (CIPs). Despite the growing understanding of co-invasion in the environment, little is known about how CIP interactions and mechanisms regulate co-invasion. Darwin’s naturalisation conundrum predicts that the coexistence of closely related species is difficult due to their structural and behavioural similarities. Nevertheless, communities containing closely related species are more susceptible to being invaded because close relatives may favour similar environments; therefore, this hypothesis should be followed in the co-invasion of CIPs. To explore whether the phylogenetic relatedness and origins of invasive species to CIPs can promote or hinder co-invasion, we conducted a controlled interaction and soil-legacy greenhouse experiment to quantify the growth response of invasive plants and their congeners. We consistently found that CIPs of identical origin were more likely to co-invade compared to CIPs of distinct origins. CIPs of distinct origins exhibited an antagonistic effect on co-invasion by allelopathy. Invasive plant-conditioned soil was more conducive to the growth of CIPs of identical origin than CIPs of distinct origins. Our results revealed the different effects of invader–invader phylogenetic relatedness on co-invader success and impact, suggesting the operation of different mechanisms across co-invasion.

Epidermal wax is strategically situated at the interface between plants and air; therefore, it plays a key role in plants’ interactions with their surroundings. It is also unstable and susceptible to light intensity. Hosta plants are shade-loving herbs with admirable flowers and leaves. Hosta ‘Halcyon’ and Hosta ensata F. Maek. are two species of Hosta with a glaucous and a glossy appearance, respectively. Light intensity can affect the composition of epicuticular wax on the leaf surface, which influences the leaf color phenotype and ornamental value. In this paper, the crystal micromorphology, content, and components of epicuticular wax on the leaves of two species of Hosta under different light conditions (10%-, 30%-, 50%-, 70%-, and 100%-intensity sunlight, relative light intensity (RLI)) have been studied using pot experiments. The results indicate that the epicuticular wax crystals of H. ‘Halcyon’ and H. ensata are tubular and platelet-like, respectively. The wax crystals of H. ‘Halcyon’ melted and formed a thick crust under 100% RLI, and those of H. ensata melted and formed a thick crust under 70% and 100% RLI conditions. The primary ingredients of the epicuticular wax of the two species of Hosta contained primary alcohols, alkanes, fatty acids, and esters; β-diketones were only detected in H. ‘Halcyon’. The quantity of epicuticular wax of H. ‘Halcyon’ reduced at first and then increased with an RLI increase, achieving its lowest value at 50% RLI, but that of H. ensata declined little by little. The amounts of C28 primary alcohols, C31 alkanes, and C18 fatty acids were significantly higher than those of other carbon atoms in the two genotypes of Hosta. The C31β-diketones content decreased with the increase in light intensity, which caused the white frost phenotype to gradually weaken in H. ‘Halcyon’.

Predicting the potential climatic suitability of invasive plants under global warming is essential for understanding invasion mechanisms and developing targeted management and control strategies. Here, we used MaxEnt and biomod2 (incorporating 10 individual algorithm models) to project potential suitable habitats for two invasive Xanthium species, Xanthium chinense and Xanthium orientale, across China. Projections were run for baseline climate conditions and two future time windows (2040–2060 and 2080–2100) across four Shared Socioeconomic Pathway scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. Under baseline climate conditions, the random-forest model predicted that X. orientale possessed the largest suitable habitat area, reaching 22.79 × 10⁵ km², whereas the MaxEnt model estimated the suitable-habitat area of X. chinense at 17.56 × 10⁵ km². Under all future climate scenarios, both species exhibit northward range expansion into higher-latitude regions of China. Under high-emission scenarios (SSP3-7.0 and SSP5-8.5), suitable habitat for X. chinense is projected to increase across North and Northeast China, whereas X. orientale shows range gains in Northwest and Northeast China. Temperature seasonality, mean temperature of the driest quarter, and population density were identified as the key environmental drivers shaping the distribution of X. orientale. Rising temperatures are expected to render high-latitude provinces such as Jilin and Heilongjiang climatically suitable for the species. Conversely, the extreme heat and humidity in southern China may constrain its suitable range by impairing growth and reproductive output. For X. chinense, annual precipitation, precipitation seasonality, mean minimum temperature in June, and population density serve as the primary environmental drivers of its distribution. Mirroring the pattern seen in X. orientale, high-latitude areas of China are projected to become core suitable habitats for X. chinense under future climates. X. chinense frequently co-occurs with X. orientale, a pattern that suggests both taxa are strongly influenced by human activity and are capable of sustaining stable populations in economically developed areas. Overall, climate warming is projected to expand the total suitable habitat for both invasive Xanthium species, with high-latitude regions in northern China emerging as newly suitable areas. This shift could amplify competitive pressure on native plant communities in these high-latitude regions.