Invasive weeds cause substantial ecological, economical, and social problems, and are currently being controlled by herbicide applications. However, how herbicides affect other ecological interactions of invasive weeds, including their symbiosis with arbuscular mycorrhizal fungi (AMF), remains poorly understood. In this study, we therefore conducted field investigation to understand how the herbicide glyphosate affects the AMF diversity in the rhizosphere of the invasive weed Solidago canadensis. We also performed a greenhouse experiment to study if AMF can contribute to herbicide resistance. The results showed that the AMF colonization rate was significantly higher in S. canadensis when exposed to glyphosate in the field or in greenhouse settings. AMF diversity was also found to be higher in the rhizosphere soil after glyphosate application in the field. AMF colonization in greenhouse experiments also positively correlated with plant growth and reduced amounts of damaged leaves and the plant's content of the stress markers flavonol and anthocyanin. Chlorophyll content was significantly enhanced by AMF colonization, regardless of glyphosate application. These results indicate that herbicide can promote AMF colonization and diversity, and that AMF can enhance the herbicide resistance of S. canadensis. These findings suggest that herbicide application may promote the spread of S. canadensis through enhanced microbial interactions, posing new eco-environmental risks.

Global change can easily cause the wetland ecosystem structure and function to be damaged by alien species. Former studies on Spartina alterniiora invasion only focused on the effect of aboveground communities, ignoring the potential regeneration of soil seed banks. Therefore, the study aimed to find the key resources that limit the S. alterniiora invasion and the regulation mechanism for S. alterniiora regeneration. Through investigating the S. alterniiora communities with different invasion stages, we studied the structure and composition of the aboveground communities and the soil seed banks, in response to the soil properties and water and nitrogen addition. The dominant competitive advantage of S. alterniiora was mainly affected by the aboveground biomass, which was regulated by soil NH4+-N and moisture content. Although the richness was same in the soil seed banks under the S. alterniiora communities with different coverage, S. alterniiora seeds maintained its specific competitive dominance. The niche breadth of S. alterniiora and the niche overlap between S. alterniiora and Tripolium pannonicum was the highest under low aboveground coverage. The soil seed bank germination experiments showed that the S. alterniiora density decreased when the soil nitrogen concentration exceeded 1 g/ kg, while the density of native species E. crusgalli and T. pannonicum decreased when the water depth above the soil surface exceeded 2 cm. The successful naturalization of S. alterniiora invasion regulated by nitrogen-water coupling is a bet-hedging of the niche and fitness differences between invasive and native species in the coastal salt marsh of eastern China.

Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn. (Pampas grass) is a perennial grass native to temperate and subtropical regions of South America. The species was introduced to western Europe for ornamental purposes during the nineteenth century, where it has become naturalized in anthropogenic and natural habitats, especially in sandy, open, and disturbed areas. Female plants of C. selloana produce thousands of seeds that are dispersed over long distances by wind and germinate readily. Its invasive success is also attributed to its ability to adapt and tolerate a wide range of environmental conditions, such as high salinity levels, long droughts, and soil chemical pollution. Cortaderia selloana usually invades human-disturbed habitats where it encounters little competition with other plants and high resource availability. However, the species can invade natural habitats, especially those with high light availability, causing biodiversity loss and changes in ecosystem functioning (e.g. alteration of succession and nutrient dynamics). The species may cause negative socio-economic impacts by reducing productivity of tree plantations, causing respiratory allergies, and decreasing the recreational value of invaded areas. Control costs are high due to the extensive root system that C. selloana develops and the high resprouting ability following physical damage. Although herbicides are effective control measures, their use is not allowed or is undesirable in all situations where the plant occurs (e.g. near riverbanks, natural protected sites). No biological control agents have been released on C. selloana to date, but the planthopper Sacchasydne subandina and the gall midge Spanolepis selloanae are promising targets.

Urban environments are vulnerable to the introduction of non-native species and sometimes contribute to their invasion success. Knowing how urban landscape features affect the population dynamics of exotic species is therefore essential to understand and manage these species. The spotted-wing drosophila, Drosophila suzukii, is a highly polyphagous fruit fly that has become a very problematic invasive species over the last decade. Because of its important damage on fruit production, D. suzukii populations have mainly been studied in agricultural areas, while their dynamics in urban landscape remain poorly explored. The objective of this study was to investigate the role of urban environment in the invasion success of D. suzukii by identifying local and landscape factors driving the abundance of the fly along seasons and urbanization gradients. To achieve this, 526 insect traps were randomly set in four different habitats (urban forest, park, riverside and town centre) along an urbanization gradient in the city of Amiens (France), between September 2018 and August 2019. The influence of landscape and local environmental variables on Drosophilidae species diversity and composition was examined using GLM and multivariate analyses. We found that Drosophilidae species richness and abundance were negatively impacted by urbanization. The Drosophilidae community was dominated by D. subobscura and D. suzukii, but their relative abundance varied with seasons. Drosophila suzukii used urban forest during winter and also during heat waves in summer. The fly was still active in this habitat in winter when the ground was covered with snow. The cover of brambles, shrubs, soil litter and dead wood debris were identified as valuable ecological indicators of the presence of D. suzukii. We highlight the role of the different components of urban environment in the ecology of D. suzukii, particularly with regard to its winter survival. These results could serve for designing management strategies in urban habitats in order to reduce the invasion success of D. suzukii.

Invasive plants are often attacked by both introduced specialist and native generalist natural enemies in new ranges. Soil fertility can potentially alter the interactions of these natural enemies with native versus invasive plants in ways that have largely unexplored implications for biological invasions and biological control. A common garden experiment was conducted to compare the performance of an introduced specialist flea beetle, Agasicles hygrophila, and/or a native generalist nematode, Meloidogyne incognita, on invasive alligator weed, Alternanthera philoxeroides, and its native congener sessile joyweed, Alternanthera sessilis, under different levels of soil nitrogen (N) and phosphorus (P). At a relatively low or moderate N and P levels, the flea beetle and the nematodes were not significantly affected by each other. Under these conditions, alligator weed responded plastically by producing more branches and biomass, as well as longer stolons, in response to attack by the flea beetle and/or the nematode, compared to sessile joyweed responses to similar levels of damage. However, under a relatively high N and P levels, nematode infestations significantly reduced flea beetle damage on alligator weed, resulting in significantly greater above- and below-ground biomass and longer stolons than plants without herbivory. In contrast, beetle herbivory significantly increased the level of nematode infestations on sessile joyweed, resulting in significantly fewer fine and coarse roots, and lower above- and below-ground biomass compared to plants without herbivory. Synthesis and applications. Our findings illustrate the importance of soil fertility in mediating interactions between specialist biocontrol agents and native generalists on native versus invasive plants. High phenotypic plasticity seems to be an important attribute that contributes to the success of invasive plants like alligator weed in relatively nutrient-poor environments. However, nutrient-rich environments could potentially confer greater growth benefits on invasive plants than on native ones by changing herbivore-herbivore interactions on plants differently. There is a great need to fully investigate the direct and indirect interactions between biocontrol agents and generalists across food webs following classical biocontrol releases. Nutrient measurements of both soil and water bodies should also be incorporated into all stages of biocontrol programmes.

Invasions of dendrophagous insects pose major threats to forest ecosystems and to the timber industry. The alien species bark beetle Polygraphus proximus Blandf. of Far Eastern origin has caused Siberian fir dieback in vast areas within several regions of Russia. Rapid spread of the pest and its outbreaks raise the issue of preserving the most important functions, including carbon sequestration, by the damaged forests. In this study, monitoring of carbon pool dynamics was carried out during 2012-2023 on four sample plots showing various degrees of damage in the southern taiga zone of Western Siberia in the Larinsky Landscape Reserve. Dynamics of the forest stands' vitality were reflected in a rapid decline of the number of viable trees and an increase in amounts of deadwood, debris, and soil composition, resulting in a transformation of the natural biological carbon cycle in the native dark coniferous ecosystems.

Many species have been intentionally introduced to new regions for their benefits. Some of these alien species cause damage, others do not (or at least have not yet). There are several approaches to address this problem: prohibit taxa that will cause damage, try to limit damages while preserving benefits, or promote taxa that are safe. In the present article, we unpack the safe list approach, which we define as a list of taxa alien to the region of interest that are considered of sufficiently low risk of invasion and impact that the taxa can be widely used without concerns of negative impacts. We discuss the potential use of safe lists in the management of biological invasions; disentangle aspects related to the purpose, development, implementation, and impact of safe lists; and provide guidance for those considering to develop and implement such lists.

Indigenous vegetation fragments in agricultural landscapes are vulnerable to creeping edge effects and stochastic extinctions on top of the effects of historic land use and disturbance which have already resulted in significant changes to baselines. Agricultural intensification can potentially increase these threats through spillover of nutrients, water, and weeds, especially in dryland ecosystems which are naturally low in nitrogen and soil moisture. We use plot-based vegetation data and soil measurements of stable isotopes of nitrogen to test whether adjacent agricultural intensification increases plant invasions into dryland shrubland fragments in Canterbury, New Zealand. Nitrogen spillover was only associated with edges adjacent to intensive agriculture. Animal effluent was the most likely source. Edges adjacent to intensive agriculture had higher dominance by exotic species, higher exotic graminoid cover, and depressed native bryophyte cover immediately adjacent to the agricultural boundary. Changes in exotic cover were due to weedy species that dominate in areas of high disturbance and nutrients rather than pasture species moving over the fenced boundary. Spillover created more abrupt environmental and vegetation gradients at the edge but didn't change the extent of the edge, which typically transitioned to the fragment core at about 40-50 m from the fragment boundary. Hence, the core vegetation remained little affected by adjacent intensification. Spatial buffers to manage fertiliser and irrigation spillover will help prevent further degradation of edge communities adjacent to intensive agriculture. However, the longer term threat to the ecological integrity of the core area of these spatially isolated fragments is likely to be random extinction and vegetation succession. The loss of spatial linkages between vegetation patches and the mosaic of vegetation at different developmental stages means that many of the species that once made up the regional species pool will be lost from this landscape without intervention.