Trees and shrubs as invasive alien species – a global review

Many biological invasions result in negative impacts on the environment and human livelihoods, but simultaneously some also provide benefits that are valued differently by various stakeholders. To inform policy and management of invasive species it is important to assess landowners’ and broader society’s knowledge and perceptions of invasive species, something which is lacking in many contexts, especially in urban settings. In this study we interviewed 153 householders living in a medium-sized South African town who had declared invasive alien trees in their gardens. Less than half of the respondents could identify the invasive tree on their property and only one-third knew that it was an invasive alien species. There was a positive association between income and education levels with exposure to media about invasive alien species and respondents’ ability to identify the species and name any other invasive alien tree species. Knowledge levels were unequal across species. Amongst those who knew the tree was an invasive alien species, reasons why they retained it in their gardens included that it would be costly or too much effort to remove, they liked the tree, that it was not causing any harm and that the property was rented and so its removal was not their responsibility. However, the majority of people (83 %) were willing to have it removed from their garden if done for free by appropriate agencies, which is promising for compliance with new regulations on invasive species implemented at the end of 2014 in South Africa. The results also highlight the need for targeted and appropriate education and awareness programs amongst urban householders on invasive alien species, relevant legislation and their obligations.

Five major invasive alien tree species in European Union forest habitat types of the Alpine and Continental biogeographical regions

Invasive alien species and planetary and global health policy

Controlling invasive alien shrub species, enhancing biodiversity and mitigating flood risk: A win–win–win situation in grazed floodplain plantations

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p < 0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p < 0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

Ecological impact of phytoinvasions in Ukraine

An explanation for successful invasion is that invasive alien species sustain less pressure from natural enemies than co-occurring native species. Using meta-analysis, we examined whether invasive species: (1) incur less damage, (2) exhibit better performance in the presence of enemies, and (3) tolerate damage more than native species. Invasive alien species did not incur less damage than native species overall. The performance of invasive alien species was reduced compared to natives in the presence of enemies, indicating the invasive alien species were less tolerant to damage than native species. However, there was no overall difference in performance of invasive alien and native species with enemies present. The damage and degree of reduction in performance of invasive alien relative to native species did not depend on relatedness to natives. Our results suggest aliens may not always experience enemy release, and enemy release may not always result in greater plant performance.

Invasive alien species threaten biodiversity with domestic gardens acting as a major pathway for the introduction of alien species. Even though the Nordic region is not currently a hotspot for biological invasions, the number of invasions in the Nordic area has been predicted to increase due to climate change. Given a time lag between introduction and invasion, many non-invasive horticultural alien species already introduced into gardens may become invasive in the future. This study aimed to identify the communication needs of Swedish garden owners regarding their management of invasive alien species. A survey among domestic garden owners, informed by topic specialists and local area experts, and interviews with garden owners were conducted in three different bio-climatic areas in a latitudinal gradient across Sweden. The questions targeted invasive alien species and their relations to biodiversity loss and climate change, as well as measures taken to control these species. Analysing the survey data collected in relation to measures taken to control invasive species, Bayesian Additive Regression Tree (BART) modelling was used to identify geographically varying communication needs of the domestic garden owners. In all study areas, the garden owners' measures taken to control invasive alien species were correlated with their strength of beliefs in having experienced local biodiversity loss. A majority of the garden owners were, moreover, uncertain about the impact of climate change on the invasiveness of alien species. In addition, the garden owners' capacity for identifying invasive alien species was often in need of improvement, in particular with respect to the species Impatiens glandulifera, Reynoutria japonica and Rosa rugosa. The results suggest that the evidence-based guidelines for effective communications we developed, have the potential to help communicators meet the local communication needs of garden owners across Sweden, in relation to the management of invasive alien garden species.

Gymnocoronis spilanthoides

:This study explores the correlates of alien plant species richness in South Africa at the scale of quarter-degree squares (QDS; ª 25 ¥ 27 km; 675 km2). We considered all alien plant species for which we had records and a subset of these – those that invade natural and semi-natural vegetation. The main source of data for species richness of indigenous and alien plant species was a national database based on herbarium specimens. For invasive alien species, data were from a national atlassing project. First, we explored the importance of energy availability and habitat heterogeneity as correlates of indigenous, alien, and invasive alien plant species richness. Linear regression models showed that species richness in the three groups of plants was explained by the same variables: a principal component of climatic factors and topographic roughness were the top-ranking variables for all groups. Next, we examined the role of indigenous species richness together with a range of environmental and human-activity variables in explaining species richness of alien and invasive alien plants. Results reveal an interplay of natural features and variables that quantify the dimension of human activities. If indigenous species richness is ignored, human-activity variables are more strongly correlated with alien species richness than with invasive alien species richness. Numbers of alien and invasive species in QDSs are significantly correlated with indigenous plant species richness in the 1,597 QDSs selected for analysis, a pattern consistent with findings from other parts of the world. Analysis of residuals between observed and predicted values showed that patterns differed between biomes. The results are useful for planning long-term intervention policy at the national scale; they suggest that areas with rich native biodiversity will face a sustained onslaught from invasive alien species and that ongoing management actions will be required to reduce and mitigate impacts from biological invasions in these areas.

How to communicate on pests and invasive alien plants? Conclusions of the EPPO/CoE/IUCN‐ ISSG/DGAV/UC/ESAC Workshop

Invasive alien plant species: From the molecular to the economic approach Invasive alien species (IAS) are plants, animals, pathogens and other organisms that are not natural in a certain ecosystem and that can cause economic or environmental damage or adversely affect human health (Ljubojevićet al., 2022) . Plant invasiveness is a globally recognized environmental and economic problem (Bang et al., 2022) . Today, the loss of biodiversity occurs due to intensive anthropogenic activities, like over-exploitation of species, urbanization and industrialization, environmental pollution, land-use shift, the introduction of IAS as well as climate change (Ren and Duan, 2017) . IAS introduction has many advantages and disadvantages, leading to numerous ecosystem services and disservices. Fostered by climate changes (Kariyawasam et al., 2019) and inherited (inner) ability to adapt to various conditions, IAS treat to suppress natural vegetation. Theoharides and Dukes (2007) defined four main stages of invasion: introduction, naturalization, colonization, and dispersal. Milanovićet al. (2020) stated that alien (especially invasive) plant species differ from native species in different morphological characteristics such as specific leaf area, height, seed size or flowering duration, where invasive species showed significant dominance in the investigated characteristics. A list of invasion-promoting traits is being amended as novel research is being conducted, from seed characteristics (Ljubojevićet al., 2021) to the whole-plant level (Bajwa et al., 2016) . With such high adaptive potential alien species develop traits that allow them to successfully cope with the changes in climate or habitats (Dukes and Mooney, 1999) . However, being very adaptive, fast-growing, and not infrequently highly ornamental, those species provide numerous ecosystem services. If viewed exclusively as 'weeds' then many resources would be invested in the eradication measures of invasive alien species, with little certainty about the desired outcome. Thus, this Research Topic gathered recent findings from around the world, providing insight into differences in gene expression, morphology, physiology and resource utilization by invasive alien species, that provided them with successful habitat invasion. As shown by (Nunes et al.) weedy invaders spread rapidly due to successful adaptation and naturalization, affecting both natural and agricultural ecosystems. One of the most invasive weed species in the sub-tropical and continental climate is Arundo donax L. from Poaceae family. Owing to the chemical and histological modifications, this species successfully inhabit the Mediterranean basin. Another invasion pathway includes soil Frontiers in Plant Science frontiersin.org 01

Distribution and management of invasive alien plant species in protected areas in Central Europe

Aim: To identify invasive aquatic alien plant species found in the Pool Malebo and some rivers in Kinshasa city, their behavior as well as their socio-economic impacts.&#x0D; Study Design: The study used a combination of purposive sampling and simple random sampling in order to select different sites where samples were collected.&#x0D; Place and Duration of Study: This study was carried out in different rivers (Pool Malebo system (Kinkole, Kingabwa), and N'sele, Funa and Lukaya rivers) of Kinshasa city in Democratic Republic of the Congo. The Pool Malebo is located along the Congo River. This was conducted between March and October 2013.&#x0D; Methodology: The collection was performed after a direct observation. The location of collection depended on sites, at Kingabwa and Kinkole, we collected invasive species in the middle of the Congo river and to achieve that, we used canoe. While at N’sele, Lukaya and Funa rivers, samples were collected at the edges. The collection took place in the morning between 7 and 11 am. Recorded species were classified either alien species or invasive alien species according to the status in the study region. The identification of collected species was carried out according to APG III. Seeing the way these species invade the environment and how they disturb the ecology of rivers, the physico-chemical characteristics of waters were measured between 7:00 and 11:00 am with the appropriate electronic probe for each parameter. For each parameter, the comparison between the sites was carried out using the ANOVA test with XLSTAT 2013 software.&#x0D; Results: Out of 151 specimens collected, 35 species have been identified of which 19 species as alien were identified and 4 proved to be invasive alien species, namely: Eichhornia crassipes, Echinochloa pyramidalis, Ludwigia peploides and Pistia stratiotes. These invasive species are used by farmers as livestock feed and also as green manure for different agricultural and farming activities, As to the physico-chemical characteristics, no significant differences were observed for the temperature and the turbidity in various sites while the pH and conductivity, there was a highly significant difference between different sites. The hydrology of these rivers is seriously disturbed due to the presence of these invasive alien species. These species constitute a serious threat in the erosion of aquatic biodiversity in the removal of native species in the formation of floating monospecific dense mats as observed.&#x0D; Conclusion: The invasion of alien species is a consequence of human activities and a concern, which affects all sectors of the society. It constitutes a true challenge for ecologists, economists, social scientists, agricultural engineers, environmentalists and other in order to develop and implement strong risk analysis frameworks and environmental impact assessments.

Alien invasive species are problematic both economically and ecologically, particularly on islands. As such, understanding how they interact with their environment is necessary to inform invasive species management. Here, we ask the following questions: What are the main functional traits that correlate with invasion success of alien plants on Robben Island? How does phylogenetic structure shape biotic interactions on the island? Using multiple approaches to explore these questions, we found that alien invasive species flower later during the year and for longer period, although flowering phenology was sensitive to alternative starting date. Additionally, we observed that alien invasive species are mostly abiotically pollinated and are generally hermaphroditic whilst their native counterparts rely on biotic pollinators, flower earlier, and are generally dioecious, suggesting that alien invasive and native species use different ecological niches. Furthermore, we found a facilitative interaction between an alien invasive legume and other invasive plants as predicted by the invasional meltdown hypothesis, but this does not influence the phylogenetic structure of plant communities. Finally, phylogenetically diverse set of native species are less receptive to alien invasive species. Collectively, our findings reveal how biotic interactions and phylogenetic relatedness structure alien invasive - native co-existence.