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Invasive alien aquatic plant species (IAAPs) cause serious ecological and economic impact and are a major driver of changes in aquatic plant communities. Their invasive success is influenced by both abiotic and biotic factors. Here, we summarize the existing knowledge on the biology of 21 IAAPs (four free-floating species, eight sediment-rooted, emerged or floating-leaved species, and nine sediment-rooted, submerged species) to highlight traits that are linked to their invasive success. We focus on those traits which were documented as closely linked to plant invasions, including dispersal and growth patterns, allelopathy and herbivore defence. The traits are generally specific to the different growth forms of IAAPs. In general, the species show effective dispersal and spread mechanisms, even though sexual and vegetative spread differs strongly between species. Moreover, IAAPs show varying strategies to cope with the environment. The presented overview of traits of IAAPs will help to identify potential invasive alien aquatic plants. Further, the information provided is of interest for developing species-specific management strategies and effective prevention measures.

Invasive alien plants are likely to be released from specialist herbivores and at the same time encounter biotic resistance from resident generalist herbivores in their new ranges. The Shifting Defense hypothesis predicts that this will result in evolution of decreased defense against specialist herbivores and increased defense against generalist herbivores. To test this, we performed a comprehensive meta-analysis of 61 common garden studies that provide data on resistance and/or tolerance for both introduced and native populations of 32 invasive plant species. We demonstrate that introduced populations, relative to native populations, decreased their resistance against specialists, and increased their resistance against generalists. These differences were significant when resistance was measured in terms of damage caused by the herbivore, but not in terms of performance of the herbivore. Furthermore, we found the first evidence that the magnitude of resistance differences between introduced and native populations depended significantly on herbivore origin (i.e., whether the test herbivore was collected from the native or non-native range of the invasive plant). Finally, tolerance to generalists was found to be higher in introduced populations, while neither tolerance to specialists nor that to simulated herbivory differed between introduced and native plant populations. We conclude that enemy release from specialist herbivores and biotic resistance from generalist herbivores have contrasting effects on resistance evolution in invasive plants. Our results thus provide strong support for the Shifting Defense hypothesis.

Identifying potentially invasive species and preventing their introduction and establishment are of critical importance in invasion ecology and land management. Although an extensive body of research has been dedicated to identifying traits that confer invasiveness, our current knowledge is still often inconclusive due to limitations in geographic extent and/or scope of traits analyzed. Here, using a comprehensive set of 45 traits, we performed a case study of invasive traits displayed by exotic woody plants in the United States (U.S.) by comparing 63 invasive and 794 non-invasive exotic woody plant species naturalized across the country. We found that invasive woody species often bear the following two key traits: vegetative reproduction and long-distance seed dispersal (via water, birds or mammals). Boosted classification tree models based on these traits accurately predicted species invasiveness (86% accuracy on average). Presented findings provide a generalized understanding of the relative importance of functional traits in identifying potentially invasive woody species in the U.S. The knowledge generated in this study can be used to improve current classification systems of non-native woody plants used by various U.S. governmental agencies and land managers.

Heavy metals (HMs) normally occur in nature and are rapidly released into ecosystems by anthropogenic activities, leading to a series of threats to plant productivity as well as human health. Phytoremediation is a clean, eco-friendly, and cost-effective method for reducing soil toxicity, particularly in weedy plants (invasive plant species (IPS)). This method provides a favorable tool for HM hyperaccumulation using invasive plants. Improving the phytoremediation strategy requires a profound knowledge of HM uptake and translocation as well as the development of resistance or tolerance to HMs. This review describes a comprehensive mechanism of uptake and translocation of HMs and their subsequent detoxification with the IPS via phytoremediation. Additionally, the improvement of phytoremediation through advanced biotechnological strategies, including genetic engineering, nanoparticles, microorganisms, CRISPR-Cas9, and protein basis, is discussed. In summary, this appraisal will provide a new platform for the uptake, translocation, and detoxification of HMs via the phytoremediation process of the IPS.

Local pathogens can accumulate as asymptomatic endophytes, making it difficult to detect the impacts of invasive species as propagators of disease in the invaded range. We used the invasive plant Ageratina adenophora to assess such accumulation. We intensively collected foliar fungal endophytes and leaf spot pathogens of A. adenophora and co-occurring neighbours and performed an inoculation experiment to evaluate their pathogenicity and host range. Ageratina adenophora harboured diverse necrotrophic pathogens; its communities of endophytes and leaf spot pathogens were different in composition and shared only a small number of fungal species. In the pathogen communities of local plant hosts, 21% of the operational taxonomic units (OTUs), representing 50% of strains, also occurred as leaf spot pathogens and/or endophytes of A. adenophora. The local pathogen community was more similar to the endophytes than to the pathogens of A. adenophora. The inoculation experiment showed that local pathogens could infect A. adenophora leaves asymptomatically and that local plant hosts were susceptible to both A. adenophora endophytes and pathogens. Ageratina adenophora is a highly competent host for local pathogens, and its asymptomatic latent pathogens are fungi primarily shared with local neighbours. This poses challenges for understanding the long-term ecological consequences of plant invasion.

1. In North America, herbicides are commonly used to control non-native invasive plants on public wildlands. Little is known about the magnitude, efficacy and financial costs of this practice, although this information is crucial for policymakers, researchers, land managers, pesticide producers and the general public. 2. In Canada and Mexico, herbicide usage data have not been tracked by agencies. In the USA, data archiving has been implemented by federal land managing agencies. However, while area sprayed and amounts of herbicides have been documented to varying degrees, efficacy and financial costs have not been recorded in a standardized and consistent manner and data publication has been insufficient. 3. Based on requested data, we estimate that in the USA, half a million hectares of public wildlands were sprayed with herbicides in 2010, representing 201 tonnes. Although nonselective, glyphosate was the most commonly used active ingredient. 4. Synthesis and applications. Increasing efforts by land management agencies to collect and share herbicide usage data is a key step towards narrowing the knowledge gap on herbicide usage in invasive non-native plant management on public wildlands. Land managers and policymakers in particular would benefit from an enhanced flow of information on efficacy, costs and effects of herbicides.

Stopping invasive species early, before they are introduced or before they have a chance to spread, is essential for effective invasive species management. With new plants introduced constantly through global trade and shifting their ranges due to climate change, proactive action to prevent invasions is more important than ever. But, before we can prevent invasions through policy, monitoring, and management, we need to know the identity of which species are invasive. Existing lists of invasive plants vary across political and jurisdictional boundaries, often rely on inconsistent knowledge of local experts, and may conflate nonnative with invasive. Here, we reviewed papers published from 1959 to 2020 to create a single consistently derived list of known invasive plants. We searched theWeb of Science core collection for “articles” containing the keywords “invasi*” and “plant” within the categories “Ecology,” “Environmental Sciences,” “Biodiversity Conservation,” and “Plant Sciences.” We also reviewed papers cited in reviews of invasive plants (see Metadata S1, Class II, Section B).We read titles and abstracts to identify papers that focused on nonnative and invasive vascular plants and included in the database any nonnative plant taxon either explicitly termed invasive in the paper or implicitly defined as invasive through a description of abundance, spread and/or impact. For 2017–2020, we included only papers that described multiple invasive plants, which are much more likely to uncover novel taxa. For each paper, we retained the reported invasive taxon name, text defining invasiveness, bibliographic information, and the country or countries in the invaded range where the study took place. We used Catalogue of Life and the Plant Taxonomic Name Resolution Source to resolve the taxonomy of the invasive taxa and compiled a list of unique invasive plants described in one or more scientific papers. We extracted data from 5,893 papers and identified 3,008 unique taxa, including 2,842 species, 96 subspecies, 29 varieties, and 41 hybrids. Of these, 2,981 taxa were resolved, while 27 were unresolved. 42% of the total unique taxa were studied once in the database. This database provides a consistent, global assessment of nonnative, invasive plant taxa. We release these data into the public domain under a Creative Commons Zero license waiver (https://creativecommons.org/share-your-work/public-domain/cc0/). Individuals who use these data for publication may cite this data paper.

Effective management of invasive plants conserves biodiversity values, reduces economic costs, and minimizes negative impacts on human health. Fostering people’s awareness of invasive plants is one of the most cost-effective approaches in preventing the spread and introduction of invasive plants. Therefore, this study aims to understand (1) people’s knowledge and risk perceptions, (2) associations between risk perceptions and demographics, and (3) people’s willingness to support current management strategies in the Metro Vancouver region, British Columbia, Canada. An online survey was carried out and received 356 responses across the region. We found that people’s knowledge and risk perceptions of invasive plants were ecologically oriented. Older respondents perceived higher risks of invasive plants. Among respondents of the same age, annual income higher than $50,000 was associated with higher levels of risk perception. Respondents who had professional and/or recreational group memberships perceived higher economic risks. Respondents highly supported activities that they could take part in directly, such as community invasive pulls and native species planting. Overall, our findings aid managers in allocating appropriate funding or tailoring outreach efforts to different aspects of invasive plants as well as groups/communities where people’s knowledge and risk perceptions of invasive plants are low.HighlightsPeople’s knowledge and risk perceptions of invasive plants were ecologically oriented.Age and income were positively associated with perceived risks of invasive plants.Respondents who had professional/recreational group memberships perceived higher risks of invasive plants.Respondents supported local governments to spend funds on active management activities.

Leucaena leucocephala (Lam.) de Wit is native to southern Mexico and Central America and is now naturalized in more than 130 countries. The spread of L. leucocephala is probably due to its multipurpose use such as fodder, timber, paper pulp, shade trees, and soil amendment. However, the species is listed in the world’s 100 worst invasive alien species, and an aggressive colonizer. It forms dense monospecific stands and threatens native plant communities, especially in oceanic islands. Phytotoxic chemical interactions such as allelopathy have been reported to play an important role in the invasion of several invasive plant species. Possible evidence for allelopathy of L. leucocephala has also been accumulated in the literature over 30 years. The extracts, leachates, root exudates, litter, decomposing residues, and rhizosphere soil of L. leucocephala increased the mortality and suppressed the germination and growth of several plant species, including weeds and woody plants. Those observations suggest that L. leucocephala is allelopathic and contains certain allelochemicals. Those allelochemicals may release into the rhizosphere soil during decomposition process of the plant residues and root exudation. Several putative allelochemicals such as phenolic acids, flavonoids, and mimosine were identified in L. leucocephala. The species produces a large amount of mimosine and accumulates it in almost all parts of the plants, including leaves, stems, seeds, flowers, roots, and root nodules. The concentrations of mimosine in these parts were 0.11 to 6.4% of their dry weight. Mimosine showed growth inhibitory activity against several plant species, including some woody plants and invasive plants. Mimosine blocked cell division of protoplasts from Petunia hybrida hort. ex E. Vilm. between G1 and S phases, and disturbed the enzyme activity such as peroxidase, catalase, and IAA oxidase. Some of those identified compounds in L. leucocephala may be involved in its allelopathy. Therefore, the allelopathic property of L. leucocephala may support its invasive potential and formation of dense monospecific stands. However, the concentrations of mimosine, phenolic acids, and flavonoids in the vicinity of L. leucocephala, including its rhizosphere soil, have not yet been reported.

Invasive non-native species (invasive species, henceforth) across all taxonomic groups are spreading globally, with numbers projected to continue growing in the future. It is difficult for governments and managers to handle this issue when the identity of invasive species or the areas of occurrence of biological invasions are not known. Here, we provide an updated list of invasive animals, plants and algae in Brazil that is fully integrated and based on the same criteria and lexicon to define invasive species across all plant and animal taxa and habitats. We list 444 invasive non-native species: 254 animals, 188 plants and 2 algae. Some of the invasive species have been present in Brazil since the beginning of the European colonization in the 1500 s, but the majority of first records in Brazil were made in the last century, with copious first records after the year 2000. The list of invasive species presented here represents the most comprehensive attempt thus far to catalog all invasive non-native species at a continental-scale for a megadiverse country. Brazil has published a national strategy with the objective of improving mechanisms and partnerships for invasive non-native species prevention, early detection and rapid response. We believe that the current list of invasive species will provide technical and scientific support for the implementation of effective measures in the management of biological invasions.