Comparing agglomerative clustering and three weed classification frameworks to assess the invasiveness of alien species across spatial scales

Invasive process of alien species is affected by not only the invaded habitats, but also the surrounding landscape matrix. Understanding the effects of landscape matrix on alien species is of great significance for controlling invasive alien species. We surveyed plant communities along the water-level fluctuating zone (WLFZ) of the Three Gorges Reservoir. Invasive status of alien plant species was evaluated. Totally 10 spatial scales of the surrounding landscape matrix in the scope of 2000 m (including WLFZ) were classified, and 14 landscape indices were applied to analyze the landscape matrix composition and configuration. Using the principal component analysis and correlation analysis, the effects of landscape matrix on the alien invasive plant species and associated scale effect were tested. Results showed that a total of 42 alien invasive plant species were found in the WLFZ, belonging to 17 families and 36 genera. Fuling was a dividing place to differentiate invasive species distribution. The number of the alien invasive species between Fuling and the Three Gorges Dam was found more than that between Fuling and Jiangjin. For the all scales (within 2000 m). The higher the landscape matrix fragmentation was, the more difficult the alien species invading. The higher landscape connectivity was, the easier the alien species invading. The effects of landscape matrix composition and configuration on the invasive plant diversity at large scales (1200-2000 m) was more significant than those at small scales (200-1000 m), in which landscape matrix composition and configuration at 1200-1400 m showed the strongest effect, demonstrating a significant spatial scale effect. Different invasive plant species showed the scale effects of landscape matrix composition and configuration. At all scales, Xanthium strumarium and Bidens frondosa showed weak correlations with landscape indices, but Bidens tripartita and Erigeron canadensis showed strong correlations. Landscape matrix was closely related to invasive plant species, and demonstrated a significant scale effect. The alien invasive plant species could be traced to the landscape matrix at large scales. Grassland and forest patches at the small scales could be used as the 'stepping stone' for the alien species transiting before they arrived at the WLFZ. In order to control alien plants in the WLFZ, land-use management and optimization should be strengthened at different scales of landscape matrix on the basis of enhancement of habitat management. A diversified comprehensive control for alien species should thus be taken into account.

Invasive alien species and planetary and global health policy

IntroductionPhylogenetic relatedness is one of the important factors in the community assembly process. Here, we aimed to understand the large-scale phylogenetic relationship between alien plant species at different stages of the invasion process and how these relationships change in response to the environmental filtering process at multiple spatial scales and different phylogenetic extents.MethodsWe identified the alien species in three invasion stages, namely invasive, naturalized, and introduced, in China. The occurrence records of the species were used to quantify two abundance-based phylogenetic metrics [the net relatedness index (NRI) and the nearest taxon index (NTI)] from a highly resolved phylogenetic tree. The metrics were compared between the three categories of alien species. Generalized linear models were used to test the effect of climate on the phylogenetic pattern. All analyses were conducted at four spatial scales and for three major angiosperm families.ResultsWe observed significantly higher NRI and NTI values at finer spatial scales, indicating the formation of more clustered assemblages of phylogenetically closely related species in response to the environmental filtering process. Positive NTI values for the invasive and naturalized aliens suggested that the presence of a close relative in the community may help the successful naturalization and invasion of the introduced alien species. In the two-dimensional phylogenetic space, the invasive species communities significantly differed from the naturalized and introduced species, indicating that established alien species need to be phylogenetically different to become invasive. Positive phylogenetic measures for the invasive aliens across the spatial scales suggested that the presence of invasive aliens could facilitate the establishment of other invasive species. Phylogenetic relatedness was more influenced by temperature than precipitation, especially at a finer spatial scale. With decreased temperature, the invasive species showed a more clustered assemblage, indicating conservatism of their phylogenetic niche. The phylogenetic pattern was different at the family level, although there was a consistent tendency across families to form more clustered assemblages.DiscussionOverall, our study showed that the community assemblage became more clustered with the progression of the invasion process. The phylogenetic measures varied at spatial and taxonomic scales, thereby highlighting the importance of assessing phylogenetic patterns at different gradients of the community assembly process.

Ecological impact of phytoinvasions in Ukraine

: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.

Risk assessment: Simultaneously prioritizing the control of invasive plant species and the conservation of rare plant species

Invasive alien species are an important component of global change, threatening biodiversity, ecosystem functioning, economy, and human health. The number of alien species that attain the invasive status has experienced an exponential increase in recent years, leading some government agencies and stakeholders to allocate substantial resources to early detection, control, mitigation, and eradication programs. To develop effective nature conservation strategies, it is crucial to understand the invasive status of alien species and to identify priority species for management at spatial scales with a biogeographical basis. Despite significant progress in producing lists of alien species at the country level, a standard methodology for species assessment within ecological regions (i.e., regions with similar environmental or biogeographical characteristics) is still lacking. Here, we develop a systematic approach to determine invasion status and to prioritize invasive alien plant species within an ecoregion. We apply this approach in the Cantabrian Mixed Forests ecoregion, which encompasses biogeographically related areas from N Portugal, NW Spain, and SW France, and is strongly affected by plant invasions. By combining scientific evidence with expert opinion on the ecological characteristics of alien plants, we identified 175 invasive plant species in the study ecoregion, of which 37 cause massive environmental and/or socio-economic impacts. For each species, we provide comprehensive information and recommendations for scientists, land managers, policy makers, and other stakeholders under a biogeographical basis. This information includes species characteristics, invasion status/level, population trends, geographic locations and range size, local abundance, environmental and socio-economic impacts, and invaded habitats. We also accounted for administrative divisions within the ecoregion to facilitate the use of such evaluations in local-scale management and conservation plans. Our framework may be applied to any ecoregion worldwide, enhancing the assessment and management of invasive species pools within biogeographically meaningful regions.

Biodiversity loss caused by invasive species may soon surpass the damage done by habitat destruction and fragmentation. Biological invasions are an important component of human-caused global environmental change. Invasive alien species are now a major focus of global conservation concern. The decisions need to be made on whether benefits derived from the invasive spread of an alien species outweigh the reduced value of ecosystem services, e.g. the loss of grazing land in areas invaded with Lantana camara and Senna occidentalis . It is necessary to consider actions to deal with the current problems caused by invasive species and to reduce the magnitude of the problem in the future. The present catalogue on invasive alien plant species of the northwestern & Western Ethiopia is therefore timely one. It focuses on some species of invasive alien plants in Ethiopia. These include the most serious invasives, such as Alternanthera philoxeroides, Cassia uniflora, Chromolaena odorata, Eichhornia crassipes, Lantana camara, Parthenium hysterophorus , Senna obtusifolia and others. I am confident that this publication will be immense value to foresters, environmentalists, field researchers and conservation managers to pay attention on the ecological impact of invasive aliens both at the species and at the ecosystem levels. Keywords : Biodiversity, invasive species, conservation, environmental change DOI : 10.7176/ALST/74-04 Publication date :May 31 st 2019

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.

Predicting the impact of climate change on species distribution at different spatial and temporal scales has emerged as one of the important areas of research in invasion ecology and conservation biology. We used MaxEnt (Maximum Entropy Algorithm) to predict the distribution of a highly invasive species, namely Parthenium hysterophorus L. under four Representative Concentration Pathway scenarios (RCPs 2.6, 4.5, 6.0 and 8.5) in 2050 and 2070 at global (world), regional (India) and local (Jammu & Kashmir State) spatial scales. Model predictions indicated differences in the extent of expansion in the distribution of this species under different climate change scenarios with marginal increase in moderately suitable area at the global scale but mostly a declining trend was noticed in its suitable and highly suitable area in future. More or less similar trend was predicted for India where increase in moderately suitable area was evident but decline in suitable and highly suitable areas was observed. In respect of Jammu & Kashmir, moderately suitable as well suitable area showed increase mostly under RCP scenarios of 6.0 and 8.5 in 2050 as well as 2070. Further analysis revealed that current centroid of P. hysterophorus is in south of Jammu and Kashmir and is predicted to shift by an average of 20.48 km in the north-west direction by 2050 and by 36.83 km by 2070. The future suitable area is likely to be around Hirapora Wildlife sanctuary in Kashmir. Pairwise comparison of the niche overlap and dynamics of P. hysterophorus between the native Americas and each of the regions (Africa, Asia, Australia and Oceania) where the species is introduced using Schoener’s D revealed variations in the niche overlap which was high between native Americas and Australia (0.70) and Africa (0.69), moderate between Americas and Asia (0.59) and low between Americas and Oceania (0.24). Exclusion of 25% of rare climatic conditions did not have any effect on the niche overlap index (D). Niche similarity test was not significant for any of the pairwise comparisons of native Americas and the continents in which the species is non-native indicating that the native niche is more similar to the exotic niche than any randomly sampled niche from the exotic range. But the niche equivalency tests showed that the environmental realized niche of P. hysterophorus in its invaded range was not totally equivalent to that in the native range indicating niche differentiation. The niche dynamic indices based on analogous and the entire climatic space in the native and introduced regions revealed a very high niche stability. A very limited niche expansion was noticed only in Asia and niche unfilling was evident in Oceania. Like niche overlap index (D), niche expansion and niche stability were not affected by the exclusion of 25% of rare climatic conditions but marginal change was noticed in niche unfilling in the Oceania. The above predictions have implications for formulation of policies at local, regional and global level for the management of this invasive species.

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.
 Study Design: The study used a combination of purposive sampling and simple random sampling in order to select different sites where samples were collected.
 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.
 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.
 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.
 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.

Invasive plant species are typically thought to pose a large threat to native biodiversity, and local-scale studies typically confirm this view. However, plant invaders rarely cause regional extirpations or global extinctions, causing some to suggest that invasive species' influence on native biodiversity may not be so dire. We aim to synthesize the seemingly conflicting literature in plant invasion biology by evaluating the effects of invasive plant species across spatial scales. We first conducted a meta-analysis on the effects of invasive plants on the species richness of invaded communities across a range of spatial extents. We then discuss studies that consider the role of invasive plants on regional spatial scales for which such meta-analyses are not possible. Finally, we develop a conceptual framework to synthesize the influence of invasive species across spatial scales by explicitly recognizing how invasive species alter species-occupancy distributions. We found a negative relationship between the spatial extent of the study and the effect size of invasive plants on species richness. Our simulation models suggest that this result can occur if invaders, either proportionately or disproportionately, reduce the occupancy of common species to a greater degree than rare species. Future studies should consider the influence of invaders on the abundance and occupancy-level changes in native species to inform how invasive plants will influence native species richness relationships across spatial scales. This approach will allow greater predictive ability for forecasting changes in biodiversity in the face of anthropogenic biological invasions and will inform invasive species management and restoration.

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.

The Country Compendium of the Global Register of Introduced and Invasive Species (GRIIS) is a collation of data across 196 individual country checklists of alien species, along with a designation of those species with evidence of impact at a country level. The Compendium provides a baseline for monitoring the distribution and invasion status of all major taxonomic groups, and can be used for the purpose of global analyses of introduced (alien, non-native, exotic) and invasive species (invasive alien species), including regional, single and multi-species taxon assessments and comparisons. It enables exploration of gaps and inferred absences of species across countries, and also provides one means for updating individual GRIIS Checklists. The Country Compendium is, for example, instrumental, along with data on first records of introduction, for assessing and reporting on invasive alien species targets, including for the Convention on Biological Diversity and Sustainable Development Goals. The GRIIS Country Compendium provides a baseline and mechanism for tracking the spread of introduced and invasive alien species across countries globally.Design Type(s)Data integration objective ● Observation designMeasurement Type(s)Alien species occurrence ● Evidence of impact invasive alien species assessment objectiveTechnology Type(s)Agent expert ● Data collationFactor Type(s)Geographic location ● Origin / provenance ● HabitatSample Characteristics - OrganismAnimalia ● Bacteria ● Chromista ● Fungi ● Plantae ● Protista (Protozoa) ● VirusesSample Characteristics - LocationGlobal countries

ABSTRACTTo prioritize weed management at the catchment scale, information is required on the species present, their relatively frequency, abundance, and likely spread and impact. The objective of this study was to classify the invasiveness of alien species that have invaded the Upper Burdekin Catchment in Queensland, Australia, at three spatial scales. A combination of three published weed classification frameworks and multivariate techniques were employed to classify species based on their frequency and cover at a range of spatial scales. We surveyed the Upper Burdekin Catchment for alien species, and for each species determined the following distribution indices — site frequency, total cover, transect frequency per site frequency and quadrat frequency per site frequency, cover per quadrat when present, cover per transect when present, and cover per site when present. These indices capture the effect of species abundance and frequency between sites (site frequency and total cover), within sites (transect frequency per site and cover per transect when present), and within transects (quadrat frequency per site frequency and cover per site). They were used to classify the species into seven groups using a hierarchical cluster analysis. The relationship between the indices was explored to determine how effective the small scale, site‐specific indices were at predicting the broader, landscape‐scale patterns. Strong correlations were observed between transect frequency per site and frequency (r 2 = 0.89) and cover per transect when present and total cover (r 2 = 0.62). This suggests that if a weed is abundant at the site level, it has the potential to occupy large areas of the catchment. The species groupings derived from the application of the three published weed classification frameworks were compared graphically to the groupings derived from the cluster analysis. One of the frameworks classified species into three groups. The other two frameworks classified species into four groups. There was a high degree of subjectivity in applying the frameworks to the survey data. Some of the data were of no relevance to the classification frameworks and were therefore ignored. We suggest that the weed classification frameworks should be used in conjunction with existing multivariate techniques to ensure that classifications capture important natural variations in observed data that may reflect invasion processes. The combined use of the frameworks and multivariate techniques enabled us to aggregate species into categories appropriate for management.