Aim: Niche-based species distribution models (SDMs) are commonly used to predict impacts of global change on biodiversity, but the reliability of these predictions in space and time depends on their ...transferability. We tested how the strategy used to choose predictors impacts the transferability of SDMs at a cross-continental scale. Location: North America, Eurasia and Australia. Method: We used a systematic approach including 50 Holarctic plant invaders and 27 initial predictorvariables, considering 10 different strategies for variable selection, accounting for the proximality, multicollinearity and climate analogy of predictors. We compared the average performance of each strategy, some of which used a large number of predictor combinations. Next, we looked for the single best model for each species across all the predictor combinations retained in the analysis. Transferability was considered as the predictive success of SDMs calibrated in the native range and projected onto the invaded range. Results: Two strategies showed better SDM transferability on average: a set of predictors known for their ecologically meaningful effects on plant distribution, and the two first axes of a principal component analysis calibrated on all predictor variables (Spc2). From the more than 2000 combinations of predictors per species across strategies, the best set of predictors yielded SDMs with good transferability for 45 species (90%). These best combinations consisted of eight randomly assembled (39 species) or uncorrelated predictors (6 species) and Spc2 (5 species). We also found that internal cross-validation was not sufficient to give full information about the transferability of a SDM to a distinct range. Main conclusion: Transferring SDMs at the macroclimatic scale, and thus anticipating invasions, is possible for the large majority of invasive plants considered in this study, but the accuracy of the predictions relies strongly on the choice of predictors. From our results, we recommend including either proximal and state-of-the-art variables or a reduced and orthogonalized set to obtain robust SDM projections.
Soil nitrogen-fixing bacterial communities (SNB) can increase the level of available soil N via biological N-fixation to facilitate successful invasion of several invasive plant species (IPS). ...Meanwhile, landscape heterogeneity can greatly enhance regional invasibility and increase the chances of successful invasion of IPS. Thus, it is important to understand the soil micro-ecological mechanisms driving the successful invasion of IPS in heterogeneous landscapes. This study performed cross-site comparisons, via metagenomics, to comprehensively analyze the effects of Solidago canadensis invasion on SNB in heterogeneous landscapes in urban ecosystems. Rhizospheric soil samples of S. canadensis were obtained from nine urban ecosystems Three replicate quadrats (including uninvaded sites and invaded sites) for each type of urban ecosystem. S. canadensis invasion did not significantly affect soil physicochemical properties, the taxonomic diversity of plant communities, or the diversity and richness of SNB. However, some SNB taxa (i.e., f_Micromonosporaceae, f_Oscillatoriaceae, and f_Bacillaceae) changed significantly with S. canadensis invasion. Thus, S. canadensis invasion may alter the community structure, rather than the diversity and richness of SNB, to facilitate its invasion process. Of the nine urban ecosystems, the diversity and richness of SNB was highest in farmland wasteland. Accordingly, the community invasibility of farmland wasteland may be higher than that of the other types of urban ecosystem. In brief, landscape heterogeneity, rather than S. canadensis invasion, was the strongest controlling factor for the diversity and richness of SNB. One possible reason may be the differences in soil electrical conductivity and the taxonomic diversity of plant communities in the nine urban ecosystems, which can cause notable shifts in the diversity and richness of SNB.
S. canadensis invasion may likely alter the community structure of soil nitrogen-fixing bacterial communities rather than the diversity or richness to facilitate its invasion process. The community invasibility of farmland wasteland may be higher than that of the other types of urban ecosystem. Meanwhile, landscape heterogeneity, rather than S. canadensis invasion, was the strong controlling factor that triggered pronounced effects on the diversity and richness of soil nitrogen-fixing bacterial communities. Display omitted
•S. canadensis invasion significantly alters the community structure of SNB.•Landscape heterogeneity significantly affects the diversity and richness of SNB.•Landscape heterogeneity significantly affects the community structure of SNB.•Community invasibility of farmland wasteland was highest in the urban ecosystems.
Clonal plants can make up a disproportionately high number of the introduced, invasive plant species in a region. Physiological integration of connected ramets within clones is a key ecological ...advantage of clonal growth. To ask whether clonal integration underlies the invasiveness of clonal plants, we tested the hypothesis that introduced clones of an invasive species will show higher capacity for integration than native clones of the same species. We conduct a greenhouse experiment on the widespread, perennial herb Hydrocotyle vulgaris. Clonal fragments consisting of pairs of connected ramets from seven sites in northwestern Spain where the species is native and seven sites in southeastern China where the species is introduced and invasive were grown for 79 days with the younger, apical ramet shaded to 30% of ambient light and the connection between ramets either severed or left intact. Severance decreased the final dry mass and ramet number of the apical ramet and its offspring in nearly all clones and increased the mass or ramet number of the basal portion of the fragment in about half of the clones, but these effects did not differ consistently between native and introduced clones. Severance did affect allocation more in introduced than in native clones, decreasing root/total mass more in apical portions and increasing it more in basal portions. Maintaining the connection between ramets caused introduced, but not native, clonal fragments to produce more leaf and less root mass and thus to lower allocation to roots. Regardless of severance, introduced clones accumulated about twice as much mass as native clones. Results suggest that introduced clones of a species can show greater effects of integration on allocation than native clones. In species such as H. vulgaris, this might increase competitiveness for light.
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•We compared introduced and native clones of Hydrocotyle vulgaris.•Introduced clones produced more mass and ramets than native ones.•Effects of clonal integration were stronger in introduced than native clones.•Clonal integration may increase competitiveness of H. vulgaris for light.
Amongst the numerous consequences of the rapid development of agriculture and urbanization, biological invasions are highlighted as having the biggest impact on the functioning of ecosystems. One of ...the alien plant species, considered in Europe and Asia to be highly invasive, is Solidago canadensis L.; and its impact on the functioning of ecosystems has been studied in numerous respects. However, knowledge about how the physico-chemical parameters of soils and biotic interactions between species shape the performance of S. canadensis in a transformed landscape is still insufficient. The aim of this study was to assess how complex soil abiotic conditions and the functional diversity of co-occurring vegetation shape the performance of S. canadensis on the wastelands abandoned by agriculture. Apart from detailed investigations of soil properties and S. canadensis biomass, to achieve our study aims, we used parameters of functional diversity, which allowed us to identify the main ecological processes determining the community assembly processes. Under higher contents of loamy fractions in soil, but lower functional richness in surroundings, S. canadensis achieved larger cover. Alongside increasing functional richness and dispersion in co-occurring vegetation, this species has demonstrated sturdy attributes when competing for water and nutrients, expressed by a higher production of rhizomes and roots. Under elevated zinc and lead levels, as well as higher functional evenness in the surroundings, the flower biomass decreased, while the biomass of stems increased. Thus, S. canadensis exhibits a highly adaptive capacity to grow in soils contaminated by heavy metals, due to the buffer properties and life strategies allowing the use of resources absorbed in loamy soils. Environmental factors seem to be more responsible for the shaping of the performance and for the colonization success of S. canadensis than biotic interactions with plants occurring in the surroundings.
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•We assessed how environment shapes the performance of an invasive species•Low functional diversity increases abundance of exotic plant on loamy soil•High functional diversity strengthens rhizome- and root-mediated competition•High heavy metals content increases stem, but decreases flower biomass•Habitat filtering was the main factor shaping the performance of invasive plant
Reynoutria japonica (Japanese knotweed) is one of the most potent global invasive plant species; however, there is still insufficient knowledge on the impact of its invasion on arbuscular mycorrhizal ...fungi (AMF, Glomeromycota). The aim of our study was to assess the condition of AMF communities under the influence of R. japonica and determine the temporal and site-dependent variability of this influence. We studied AMF spore number, species richness, and composition as well as biomass in pairs of adjacent plots encompassing R. japonica and resident plant species. We established these pairs of plots in different habitat conditions (light and heavier soil conditions), and we sampled them four times (two spring and two summer seasons) to check if the potential impact of the invader on AMF communities is soil- and/or season-dependent. We found that the invasion reduced AMF spore number, species richness, and biomass, but had no effect on AMF species composition. AMF parameters varied over time (spore number, species composition and biomass) and depended on soil condition (species richness), but were barely affected by interactions between the studied factors. The lower performance of AMF communities in R. japonica plots was probably due to the displacement of resident mycorrhizal plant species. This displacement was not complete as some mycorrhizal plants, especially spring ephemerals, managed to survive the invasion. These were probably responsible for the maintenance of AMF communities in the patches of R. japonica. In conclusion, AMF communities are negatively affected by the invasion, but R. japonica does not entirely eliminate AMF, which is optimistic from the viewpoint of restoring sites invaded by this non-mycorrhizal alien plant species.
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•The impact of Reynoutria japonica invasion on AMF communities was studied.•The invasion reduced AMF spore number, species richness, and biomass.•R. japonica had no impact on AMF species composition.•The invasion effects on AMF did not interact with season and soil type.•R. japonica reduced AMF abundance but did not completely eliminate AMF.
•Most IPS in Germany have not yet filled their potentially suitable habitat.•Habitat suitability changes are species-specific and mainly driven by climatic factors.•Despite mixed responses, most IPS ...in Germany benefit from climate change.•Vegetation types derived from remote sensing data can improve habitat modelling.
The increase in the spread of invasive plant species (IPS) causes major disturbances to ecosystem functions. Monitoring systems are considered necessary to implement effective measures against their spread. We created species distribution models that identify the potentially suitable habitat under present and future climatic conditions for 46 IPS in Germany and incorporated habitat types obtained through remote sensing methods to assess their influence on habitat suitability.
We included 18 environmental variables that describe habitat characteristics, including soil type, altitude, land use, transport infrastructure, temperature and precipitation. Models were based on two machine learning techniques: Support Vector Machines (SVM) and Boosted Regression Trees (BRT). SVM classification of Natura2000 habitat types using MODIS reflectance data was included to provide a vegetation type-based approach to interspecific competition. We integrated predicted climate variables to determine changes in habitat suitability for two forecast periods (2041–2060 and 2061–2080) and three Representative Concentration Pathways.
Averaging over all species, the models showed good predictive power, with the quality of BRT (AUC 0.861; RMSE 0.225) surpassing that of SVM (AUC 0.804; RMSE 0.285). We observe that the majority of the species have not yet filled their potentially suitable habitat. An increase in habitat suitability for predicted climatic conditions is implied for most species.
Our results indicate that the dynamics of biological invasions will intensify with anticipated climatic changes. Climate factors, soil type and transport infrastructure are of great relevance for the distribution of IPS, while interspecific competition, indirectly assessed through the distribution of habitat types, is only relevant for some species.
•We studied regional effects of agricultural history on forests in northern NJ.•Post-agricultural forests comprised 46% of forests in the region.•Invasive plants increased and native tree ...regeneration decreased in post-ag forests.•Post-ag forest soils had higher pH and lower carbon, %sand, nitrogen, iron and EC.•Post-ag changes were highly consistent across regional environmental gradients.
We studied the effects of agricultural land use history on present-day forest conditions at large spatial and temporal scales. We used historic forest maps from the late 1800s to document the spatial extent of primary and post-agricultural forest cover in the 8080 km2 area of northern New Jersey outside the coastal plain, measuring the structure and composition of their vegetation and soils in 72 paired plots, and comparing the responses to agricultural land use history across regional and landscape-level environmental gradients. We estimated a 25% net increase in forest cover from the late 1800’s to 2015, with a 26% decline in primary forests during the same time. As little as 5–14% of the land area of some ecoregions are occupied by primary forests today. Post-agricultural forests comprise >46% of total forest cover and up to 72–77% in some ecoregions. Forest vegetation and soils differed significantly in the two forest types, with 8–11x greater invasive shrub and liana cover in post-ag forests, 2–5x more invasive species than native species, and reduced tree regeneration in seedling and sapling size classes (37–63%). Post-ag forest soils had a higher pH and associated base mineral concentrations (Ca, Mg), lower nutrients (NH4, %N), electrical conductivity and organic content (%C, % organic matter), and changes to soil texture (lower % sand, higher % silt and clay). Variation in these changes across large spatial and temporal scales showed few to no relationships with bedrock/surface geology, glacial history, soils, topography, forest age class or integrity metrics, indicating the robustness of these changes across a wide range of environmental contexts and conditions. Comparisons to past primary forest conditions in the same region (1948–1973) showed even greater deficits in tree regeneration and increases in invasive abundance in post-ag forests than present-day comparisons suggested. The results indicate the significance of agricultural history as a major driver of long-term and large-scale forest change. Greater protection of primary forests is needed along with prioritizing the respective needs of these different forest land use history types for stewardship and restoration in the future.
Abstract Amaranthus palmeri S. Watson is one of the most troublesome weed species worldwide, and is considered one of the most devastating weeds in agricultural fields in the United States. Recently, ...A. palmeri populations have spread beyond their native range, into the Mediterranean region, and have been reported in several European countries. Resistance to 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS) and acetolactate synthase (ALS) inhibitors have been found in European populations, exacerbating the management problems with this species in the Mediterranean region. While the biology, ecology, herbicide resistance mechanisms, and agricultural significance of A. palmeri have been studied, there remains a need to discuss how A. palmeri 's unique reproductive traits influence its ability to adapt to various environments, especially as an invasive species spreading into new habitats. We review how the genetic and genomic characteristics of A. palmeri interact with aspects of its reproductive biology, including its breeding system, and alter its ability to hybridize and develop herbicide resistance. Finally, we discuss the breeding system of A. palmeri in the context of weed management, and explore different approaches such as irradiated pollens, genetic manipulations, and RNA interference (RNAi).
Cadmium (Cd) is one of the toxic heavy metal that negatively affect plant growth and compromise food safety for human consumption. Nitrogen (N) is an essential macronutrient for plant growth and ...development. It may enhance Cd tolerance of invasive plant species by maintaining biochemical and physiological characteristics during phytoextraction of Cd. A comparative study was conducted to evaluate the phenotypical and physiological responses of invasive W. trilobata and native W. chinensis under low Cd (10 µM) and high Cd (80 µM) stress, along with different N levels (i.e., normal 91.05 mg kg-1 and low 0.9105 mg kg-1). Under low-N and Cd stress, the growth of leaves, stem and roots in W. trilobata was significantly increased by 35–23%, 25–28%, and 35–35%, respectively, compared to W. chinensis. Wedelia trilobata exhibited heightened antioxidant activities of catalase and peroxidase were significantly increased under Cd stress to alleviate oxidative stress. Similarly, flavonoid content was significantly increased by 40–50% in W. trilobata to promote Cd tolerance via activation of the secondary metabolites. An adverse effect of Cd in the leaves of W. chinensis was further verified by a novel hyperspectral imaging technology in the form of normalized differential vegetation index (NDVI) and photochemical reflectance index (PRI) compared to W. trilobata. Additionally, W. trilobata increased the Cd tolerance by regulating Cd accumulation in the shoots and roots, bolstering its potential for phytoextraction potential. This study demonstrated that W. trilobata positively responds to Cd with enhanced growth and antioxidant capabilities, providing a new platform for phytoremediation in agricultural lands to protect the environment from heavy metals pollution.
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•Cadmium has detrimental effects on plant growth and food safety.•Nitrogen plays a role in enhancing the tolerance of plants to cadmium.•W. trilobata effectively regulates Cd accumulation in shoots and roots.•W. trilobata heightened antioxidant activity along with flavonoid content.
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