Detecting shifts in trait values among populations of an invasive plant is important for assessing invasion risks and predicting future spread. Although a growing number of studies suggest that the dispersal propensity of invasive plants increases during range expansion, there has been relatively little attention paid to dispersal patterns along elevational gradients. In this study, we tested the differentiation of dispersal-related traits in an invasive plant, Galinsoga quadriradiata, across populations at different elevations in the Qinling and Bashan Mountains in central China. Seed mass–area ratio (MAR), an important seed dispersal-related trait, of 45 populations from along an elevational gradient were measured, and genetic variation of 23 populations were quantified using inter-simple sequence repeat (ISSR) markers. Individuals from four populations were then planted in a greenhouse to compare their performance under shared conditions. Changing patterns of seed dispersal-related traits and populations genetic diversity along elevation were tested using linear regression. MAR of G. quadriradiata increased, while genetic diversity decreased with elevation in the field survey. In the greenhouse, populations of G. quadriradiata sourced from different elevations showed a difference response of MAR. These results suggest that although rapid evolution may contribute to the range expansion of G. quadriradiata in mountain ranges, dispersal-related traits will also likely be affected by phenotypic plasticity. This challenges the common argument that dispersal ability of invasive plants increases along dispersal routes. Furthermore, our results suggest that high-altitude populations would be more effective at seed dispersal once they continue to expand their range downslope on the other side. Our experiment provides novel evidence that the spread of these high-altitude populations may be more likely than previously theorized and that they should thus be cautiously monitored.
Aims Shifts in the realized niches of exotic species may play an important role in their invasion. Galinsoga quadriradiata has invaded China widely and occupied many climate zones that are different from its native range. We addressed the climatic niche shift of G. quadriradiata, and evaluated how this could contribute to its invasion in China. Methods We used the Maxent model to predict the potential distribution of G. quadriradiata using its native and invaded range occurrences and climatic variables. Principal component analysis was conducted to measure climatic niche shifts of G. quadriradiata during its invasion in China. Important Findings The models revealed only 32.7% niche overlap between the native and invasive populations. The niche similarity of the two populations was significantly low (Schoener’s D = 0.093, P<0.005), suggesting the occurrence of a niche shift. The envelop and center of the realized climatic niche in China has shifted to lower temperature and less precipitation compared to that in its native range. The majority of invaded areas in southern China are in the stabilizing zone, whereas the colonization and adaptation zones are predicted to be at the leading edge of G. quadriradiata invasion in northern China. This suggests that the regional distribution of G. quadriradiata may be in a quasi-equilibrium state, and that the species continues to invade environmentally suitable areas. Alterations in G. quadriradiata’s niche would help to explain why this species is so invasive in China.
Fungal communities related to invasive plants may change with elevational gradient, which may affect the performance and invasiveness of invasive plants. Our recent study revealed that the root AMF colonization rate of invasive plant Galinsoga quadriradiata decreased with elevation. However, it is still unclear whether it is caused by the changes of the fungal community along elevation. To address this issue, we used high-throughput sequencing techniques, functional groupings, and linear statistics to examine how the fungal communities in the rhizosphere and roots of G. quadriradiata changed across the elevation in Qinling and Bashan Mountains, China. Our results revealed that species diversity and composition of both the rhizosphere and root fungal communities changed along the elevation. The Shannon-Wiener diversity index in the rhizosphere increased with elevation while that in the roots decreased. In contrast, the relative abundance of pathotroph in the rhizosphere decreased while that in the roots increased with elevation. These suggest that when the invasive plant colonizes into high altitudes, it may not suffer from limited rhizosphere fungal symbionts, but rather the ability of the plant to create and maintain these associations decreases. The invader tends to accumulate more pathogenic fungi in the roots while reducing the dependence on symbiotic fungi during expansion into higher elevations. All in all, our results highlight that the interactions between invasive plants and fungal community substantially changed along elevation, and belowground interactions may be key in our understanding of how invasive plants derive success in stressful, high-elevation environments.
Kaolin was used as an adsorbent to remove toxic graphene oxide (GO) from an aqueous solution. The adsorption properties and mechanism of GO by Kaolin were systematically studied by various characterization techniques and methods. The effects of pH, amount of absorbent, and initial concentration of GO on the adsorption of GO by Kaolin were studied in detail. The results show that the interaction between GO and Kaolin is realized by the O-C=O bond, and the adsorption of GO by Kaolin is a chemical adsorption process. Under the optimized conditions (pH=3, T=303 K, equilibrium time = 6 h, C0 = 60 mg·L-1), the removal rate of GO reached 97.1% (Kaolin=70 mg), and the adsorption capacity reached 45.3 mg·g-1 (Kaolin=50 mg). According to the experimental results, Kaolin may be a promising material, which can effectively eliminate GO from an aqueous solution. The results of this study provide key information about the migration and potential fate of GO in the natural environment.
During the range expansion of invasive plants, competitors shared different co-evolutionary history with invasive plants, as well as population differentiation, would have different effects on the response of invaders to global change factors such as increased nitrogen deposition. To address these challenges, we conducted a greenhouse experiment to explore the synergistic effects between population differentiation during range expansion and competitors on the invasion of Galinsoga quadriradiata in response to increased nitrogen deposition. Competitors (new or old that shared short or long co-evolutionary history with the invader, respectively) were set to compete with the invasive central and edge populations under different nitrogen addition treatments. Galinsoga quadriradiata from the central population (i.e., with longer residence time since invasion) showed significantly higher total mass, reproduction, interspecific competitiveness when compared to the individuals from the edge population. Nitrogen addition promoted growth and reproductive performance of G. quadriradiata in single-culture, in the presence of competitors this effect was weakened. The old competitors acted more effectively than new competitors in inhibiting the invader performance. Our results indicate that population differentiation on growth and competitiveness occurred during the range expansion of G. quadriradiata, with the central population displaying higher invasiveness. The co-evolutionary history between invasive species and its competitors has been suggested to be probably not in favor of invasive plants. Our results highlight the synergistic and non-additive role of population differentiation and shared co-evolution history between invasive species and its competitors in the range expansion of invaders in the context of global change factors.
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