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A central question in invasion biology is whether adaptive trait evolution following species introduction promotes invasiveness. A growing number of common‐garden experiments document phenotypic differences between native‐ and introduced‐range plants, suggesting that adaptive evolution in the new range may indeed contribute to the success of invasive plants. However, these studies are often subject to methodological pitfalls, resulting in weak evidence for post‐introduction adaptive trait evolution and leaving its role in the invasion process uncertain. In a common‐garden glasshouse study, we compared the growth, life‐history, and reproductive traits of 35 native‐ and introduced‐range Polygonum cespitosum populations. We used complementary approaches including climate‐matching, standardizing parental conditions, selection analysis, and testing for trait–environment relationships to determine whether traits that increase invasiveness adaptively evolved in the species' new range. We found that the majority of introduced‐range populations exhibited a novel trait syndrome consisting of a fast‐paced life history and concomitant sparse, reduced growth form. Selection analysis confirmed that this trait syndrome led to markedly higher fitness (propagule production) over a limited growing season that was characteristic of regions within the introduced range. Additionally, several growth and reproductive traits showed temperature‐based clines consistent with adaptive evolution in the new range. Combined, these results indicate that, subsequent to its introduction to North America over 100 generations ago, P. cespitosum has evolved key traits that maximize propagule production. These changes may in part explain the species' recent transition to invasiveness, illustrating how post‐introduction evolution may contribute to the invasion process. [ABSTRACT FROM AUTHOR]

It is frequently thought that global environmental changes, and especially the concomitant changes in environmental variability, could further increase the success of invasive species in native resident communities. However, very few studies explicitly tested this, and it remains unknown whether invasive and noninvasive alien species respond differently to resource fluctuations in resident communities.We grew 10 invasive and 10 noninvasive species as target species in pot‐mesocosms with four different synthetic native resident communities under six nutrient treatments differing in overall nutrient availability and temporal fluctuations in nutrient supply (constant low, constant high, gradual increasing, gradual decreasing, single large pulse, multiple smaller pulses). With the exception of plants in the constant low treatment, the plants were supplied the same total amount of nutrients during the experiment. We tested whether high‐nutrient availability and fluctuations in nutrient supply increased performance of both invasive and noninvasive alien plants within native resident communities, and whether invasive ones benefited more than noninvasive ones.We found that the increase in biomass in response to nutrient addition was stronger for invasive than for noninvasive alien species. However, as the native competitors benefited even more from nutrient addition, the relative biomass of the alien target‐plant species, particularly the noninvasive ones, decreased. When the nutrient supply gradually increased, biomass of alien targets as well as native competitors decreased compared to the plants in the constant nutrient‐supply treatment. Surprisingly, when nutrients were supplied as a single large pulse, the absolute and relative biomass of the alien target plants decreased. The reduction in relative biomass was even stronger for invasive than for noninvasive alien species, and a similar pattern was found when nutrients were supplied as multiple smaller pulses.Our results confirm previous findings that invasive alien species benefit more from nutrient addition than noninvasive alien species. However, in contrast to previous findings, our results suggest that nutrient fluctuations can suppress biomass of alien plants relative to that of natives, at least when the natives are themselves very successful, common species. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

Detecting exotic plant species is essential for invasive species management. By accounting for factors likely to affect species’ detection rates (e.g. survey conditions, observer experience), detectability models can help choose search methods and allocate search effort. Integrating information on species’ traits can refine detectability models, and might be particularly valuable if these traits can help improve estimates of detectability where data on particular species are rare. Analysing data collected during line transect distance sampling surveys in Indonesia, we used a multi-species hierarchical distance sampling model to evaluate how plant height, leaf size, leaf shape, and survey location influenced plant species detectability in secondary tropical rainforests. Detectability of the exotic plant species increased with plant height and leaf size. Detectability varied among the different survey locations. We failed to detect a clear effect of leaf shape on detectability. This study indicates that information on traits might improve predictions about exotic species detection, which can then be used to optimise the allocation of search effort for efficient species management. The innovation of the study lies in the multi-species distance sampling model, where the distance-detection function depends on leaf traits and height. The method can be applied elsewhere, including for different traits that may be relevant in other contexts. Trait-based multispecies distance sampling can be a practical approach for sampling exotic shrubs, herbs, or grasses species in the understorey of tropical forests. [ABSTRACT FROM AUTHOR]

Questions The impact of invasive species on community structure and function varies, yet it is difficult to predict. Different hypotheses have been proposed to predict invasive species establishment and impact on resident communities, based on characteristics of the resident community and/or environmental conditions. Invasive species, however, interact with both native and exotic species. The interaction with exotic species is important, as it can result in secondary invasion or greater impact on native species. Smooth brome ( Bromus inermis Leyss.) is a widely planted forage crop, but also a harmful invasive species in North American grasslands, yet little is known about the variability of its impact on resident communities. We ask (1) whether smooth brome has a consistent impact on community structure and function; (2) which biotic and abiotic conditions are associated with smooth brome's impact on resident communities; and (3) whether smooth brome has a similar impact on native and exotic species, and which biotic or abiotic conditions drive the interaction of smooth brome with native and exotic species. Location Eight grasslands throughout Alberta, Canada. Methods We used space-for-time substitutions to quantify smooth brome's impact on different aspects of community structure and function, and whether it varies depending on species richness, productivity, temperature, precipitation and variation in precipitation. Results Smooth brome had a consistent negative impact on community structure and function. However, the strength of the effect depended on aspects of the local community. Smooth brome impacts on species richness were higher in species-rich areas, while impact on resident species biomass was larger in productive, warmer and more variable sites. In most sites the negative effect of smooth brome on species richness was higher for native species, compared to exotics. Impact on native and exotic species richness was larger in species-rich and more variable sites, respectively. Conclusions Understanding and predicting smooth brome's impact on community structure and function can help managers prescribe management plans to reduce negative impacts of smooth brome on native communities. Predicting the interaction of smooth brome with exotic species may be just as important when planning management strategies, to avoid secondary invasion and/or the accumulation of exotic species. [ABSTRACT FROM AUTHOR]

Specific scope This Standard describes procedures for control of invasive alien aquatic plants. This Standard focuses on invasive alien aquatic plants in freshwaters and wetlands, i.e. invasive alien plants having specialized adaptations for growing and reproducing in freshwaters. This Standard does not cover algae, nor plants of marine or brackish environments. Specific approval and amendment First approved in 2014-09. [ABSTRACT FROM AUTHOR]

Pathway analysis represents an effective means of identifying emerging invasive alien species. For plants, a significant number of invasions have been caused by plant species originally voluntary introduced as ornamentals. The pathway analysis for terrestrial ornamental plants imported from East Asia has been undertaken to provide information on the imports and to identify emerging terrestrial invasive alien plants. Data for terrestrial ornamental plants imported from East Asia into Austria, France, Italy, the Netherlands and Turkey was assembled at the genus level. Thousands of species of plants for planting are imported from East Asia in very large volumes. However, despite the fact that the data could only been analyzed at the genus level, it is considered that only a very limited number of taxa would become invasive. The potentially invasive alien species are already widely available in European nurseries and are principally produced within the European Union. [ABSTRACT FROM AUTHOR]

Building relationships with stakeholders involved in species introductions is increasingly considered as an effective means to mitigate invasion risks. The horticultural industry is of particular importance to the regulation of alien plants. This paper presents the initial experiences with a recently implemented environmental policy called 'Duty to Inform' which aims to limit the risk of plant invasions through alien horticultural plants in Switzerland. The Duty to Inform requires horticulturalists to inform their customers about risks of black-listed plants and watch list plants. In a joint effort with the Swiss horticultural industry and Swiss authorities, the authors examined customers' acceptance of plant labels as a means to supply information, and horticulturalists' attitudes towards the Duty to Inform regulation, and their willingness to act pro-environmentally. Plant labels were found to be an effective means to inform customers about plant invasion risks and appropriate handling of risk species. The results indicate that among Swiss horticulturalists the awareness of the invasive species problem and the willingness to act is high. Horticulturalists had positive attitudes towards the Duty to Inform regulation and other actions to reduce invasion risks. The authors suggest that these positive attitudes might stem from an active participation of horticulturalists in the development of invasive species regulations in Switzerland. [ABSTRACT FROM AUTHOR]

The article provides information on the Brazilian peppertree (Schinus terebinthifolia Raddi), which is considered as one of the most serious invasive plants in Florida and classified under Category I invasive plant by the Florida Exotic Plant Pest Council (FLEPPC). It discusses the origin of Brazillian peppertree, its impacts in Florida which invaded an estimated 283,000 hectares of south and central state, its management and biological control.

The aquarium trade has been shown to be a source for introductions of nonnative aquatic macrophyte species. Improvements are needed in identification, labeling, and retailer awareness of banned aquatic plants. In the state of Connecticut, United States, 20 nonnative macrophytes are banned from sale by state statute. At least 13 of these species are already established in the state's lakes, while the remainder are either present in near-shore wetlands or absent but thought to be capable of naturalizing. We documented the sale of banned plants in the Connecticut aquarium trade by visiting 23 retailers in 2008 and 47 retailers in 2010. Plants that resembled Connecticut's banned species were purchased and identified using standard morphological techniques. In 2010, we also employed DNA sequencing to aid in plant identification. We found that nearly 30% of stores sold banned aquatic plants includingCabomba caroliniana,Egeria densa,Myriophyllum aquaticum, andMyriophyllum heterophyllum.Cabomba carolinianarepresented more than half of the banned species being sold; it was found in 17% of the stores in 2008 and 19% of the stores in 2010.Egeria densawas mislabeled 50% of the time asEgeria najasorAnacharis najas; it was sold in 11% of the stores in 2008 and 17% of the stores in 2010. In 2010,Myriophyllumspecimens from 6 stores were unidentifiable using morphological characteristics. Using these techniques, one of the specimens was identified asMyriophyllum heterophyllum. Of the 29 chain stores surveyed, 7% sold banned species compared to 56% of the 27 independent stores. [ABSTRACT FROM PUBLISHER]

1. A mechanistic understanding of seed dispersal is important for understanding and predicting dispersal patterns and spatial population dynamics. We analysed a mechanistic model for the ballistic dispersal of the widespread invasive plant Impatiens glandulifera. The model deterministically simulates individual seed trajectories, including the interaction between seeds and atmospheric winds. It is fully specified using independently measured plant traits and wind velocities. 2. To parameterise the model, we conducted field surveys and analysed high-speed video footage of seed release. We explicitly incorporated intraspecific variation in key biological parameters (seed size and mass, release height, velocity and direction), as well as variation in wind velocities. This parameter variation introduces process-based stochasticity to the deterministic model, allowing the derivation of population-level dispersal kernels. 3. Analysis of the parameterised model showed complex interactions between plant dispersal parameters and wind conditions. For example, the optimal seed launch angle in still wind is 32° above horizontal, but this rises in stronger tailwinds. In a headwind, it can be optimal to either launch the seed straight upwards or slightly below the horizontal. Headwinds also blow projected seeds back towards the source, initially decreasing but then increasing net dispersal distance, which can reverse the positive effect of seed release height on dispersal distance. 4. To validate the model, we performed a field experiment in which seeds were trapped up to 6 m from potted I. glandulifera plants. Seed dispersal was biased in the direction of the prevailing wind, which was only reproduced by simulations of the model that included the wind modification of ballistic trajectories. The correspondence between the model and the data was good ( R2 = 0.882), but improved if seed release was biased to occur in more windy conditions ( R2 = 0.945) as might occur through mechanical disturbance to the seed pods. 5. Synthesis. Our validated model provides a functional understanding of seed dispersal in I. glandulifera. The model reveals surprisingly complex interactions between the ballistic dispersal mechanism and the wind and shows how population-level dispersal patterns emerge from intraspecific variation in dispersal traits. [ABSTRACT FROM AUTHOR]

The Table Mountain National Park is a 265 km⊃2 protected area embedded within a city of 3.5 million people. The park contains an extremely diverse flora with many endemic species, and has been granted World Heritage Site status in recognition of this unique biodiversity. Invasive alien plants are arguably the most significant threat to the conservation of this biodiversity, and the past decade has seen the implementation of aggressive programs aimed at the removal of invasions by these plants. These invasive alien plants include several species of trees, notably pines (Pinus species) and eucalypts (Eucalyptus species), which historically have been grown in plantations, and which are utilized for recreation by the city's residents. In addition, many citizens regard the trees as attractive and ecologically beneficial, and for these reasons the alien plant control programs have been controversial. I briefly outline the legal obligations to deal with invasive alien plants, the history of control operations and the scientific rationale for their implementation, and the concerns that have been raised about the operations. Evidence in support of control includes the aggressive invasive nature of many species, and the fact that they displace native biodiversity (often irreversibly) and have negative impacts on hydrology, fire intensity, and soil stability. Those against control cite aesthetic concerns, the value of pine plantations for recreation, the (perceived) unattractive nature of the treeless natural vegetation, and the (incorrect) belief that trees bring additional rainfall. The debate has been conducted through the press, and examples of perceptions and official responses are given. Despite opposition, the policy promoting alien plant removal has remained in place, and considerable progress has been made towards clearing pine plantations and invasive populations. This conservation success story owes much to political support, arising largely from job creation, and a strong body of scientific evidence that could be cited in support of the program. [ABSTRACT FROM AUTHOR]

Plant species, their parts and derivatives have been transferred by humans since the beginning of history: unintentionally (e.g., with propagules adhering to clothes) or intentionally (e.g., when species or parts of them were used for food or as sources of tools). Numerous plant transfers resulted in species becoming permanently naturalized in new areas, in some cases with extremely negative effects for the region to which they were brought. However, transfers also often proved neutral or even beneficial. This article does not intend to give a comprehensive survey of the history and the consequences of plant transfers in space and time but presents and discusses illustrative examples of plant movements by people. Special emphasis is given to effects on islands and to historical, political, and economic aspects of long-distance plant trade in the Old World often little known by botanists. [ABSTRACT FROM AUTHOR]

Background: Overcoming boundaries is crucial for incursion of alien plant species and their successful naturalization and invasion within protected areas. Previous work showed that in Kruger National Park, South Africa, this process can be quantified and that factors determining the incursion of invasive species can be identified and predicted confidently. Here we explore the similarity between determinants of incursions identified by the general model based on a multispecies assemblage, and those identified by species-specific models. We analyzed the presence and absence of six invasive plant species in 1.0×61.5 km segments along the border of the park as a function of environmental characteristics from outside and inside the KNP boundary, using two data-mining techniques: classification trees and random forests. Principal Findings: The occurrence of Ageratum houstonianum, Chromolaena odorata, Xanthium strumarium, Argemone ochroleuca, Opuntia stricta and Lantana camara can be reliably predicted based on landscape characteristics identified by the general multispecies model, namely water runoff from surrounding watersheds and road density in a 10 km radius. The presence of main rivers and species-specific combinations of vegetation types are reliable predictors from inside the park. Conclusions: The predictors from the outside and inside of the park are complementary, and are approximately equally reliable for explaining the presence/absence of current invaders; those from the inside are, however, more reliable for predicting future invasions. Landscape characteristics determined as crucial predictors from outside the KNP serve as guidelines for management to enact proactive interventions to manipulate landscape features near the KNP to prevent further incursions. Predictors from the inside the KNP can be used reliably to identify high-risk areas to improve the cost-effectiveness of management, to locate invasive plants and target them for eradication. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

In this paper, a number of seventeen alien plant species are presented, one of them being now for the first time reported in Romania (Sedum sarmentosum Bunge). Some species are mentioned for the first time in the flora of Moldavia (Aster novae-angliae L., Cenchrus incertus M. A. Curtis, Chenopodium pumilio R. Br., Fraxinus americana L., Lindernia dubia (L.) Pennell, Petunia × atkinsiana D. Don, Solidago gigantea Aiton, Tagetes erecta L.) or Transylvania (Kochia sieversiana (Pallas) C. A. Mey.), and some are reported from new localities (seven species). For each species, there are presented general data on the geographical origin, its distribution in Europe and worldwide, as well as its invasion history and current distribution in Romania. Some of these species manifest a remarkable spreading tendency, expanding their invasion area in Romania. Voucher specimens were deposited in the Herbarium of University of Agricultural Sciences and Veterinary Medicine Iaşi (IASI). [ABSTRACT FROM AUTHOR]

A prevalent question in the study of plant invasions has been whether or not invasions can be explained on the basis of traits. Despite many attempts, a synthetic view of multi-trait differences between alien and native species is not yet available. We compiled a database of three ecologically important traits (specific leaf area, typical maximum canopy height, individual seed mass) for 4473 species sampled over 95 communities (3784 species measured in their native range, 689 species in their introduced range, 207 in both ranges). Considering each trait separately, co-occurring native and alien species significantly differed in their traits. These differences, although modest, were expressed in a combined 15% higher specific leaf area, 16% lower canopy height and 26% smaller seeds. Using three novel multi-trait metrics of functional diversity, aliens showed significantly smaller trait ranges, larger divergences and a consistent differentiation from the median trait combination of co-occurring natives. We conclude that the simultaneous evaluation of multiple traits is an important novel direction in understanding invasion success. Our results support the phenotypic divergence hypothesis that predicts functional trait differences contribute to the success of alien species. [ABSTRACT FROM AUTHOR]

Indigenous forests in remote islands are generally impoverished of secondary successional tree species. After canopy disturbances, the same indigenous tree species seem to resume dominance by a process known as ''autosuccession'' or ''direct succession.'' Primary forest tree species are mostly colonizer species. Mature island forests are difficult to categorize as either pioneer, successional, or climax forests by their canopy species composition. Climax forests, which characterize mature forests in less-isolated areas, are typically of distinctly different canopy species composition than the pioneer forests. In central Canada, for example, pioneer pine forests are replaced in succession by mixed hardwood/softwood forests under exclusion of fire. This process is known as ''normal replacement succession'' or ''obligatory succession.'' Another well-known ecological concept distinguishes between ''primary'' and ''secondary'' forests in the continental tropics. Secondary forests are formed by fast-growing relatively short-lived second-growth species, which quickly assemble after major disturbances. It usually takes a long time for primary tropical rain forest trees to reappear in secondary forests. In contrast, primary island forests rarely include fast-growing indigenous canopy species that form such secondary forests in the continental tropics. Instead, secondary forests in islands are now made up mostly of introduced species. In this paper I attempt to evaluate alien plant invasion in remote islands in view of these concepts of ecological succession. [ABSTRACT FROM AUTHOR]

The paper examines the role of feral sheep ( Ovis aries) in facilitating the naturalization of alien plants and degrading a formerly robust and stable ecosystem of Socorro, an isolated oceanic island in the Mexican Pacific Ocean. Approximately half of the island is still sheep-free. The other half has been widely overgrazed and transformed into savannah and prairie-like open habitats that exhibit sheet and gully erosion and are covered by a mix of native and alien invasive vegetation today. Vegetation transects in this moderately sheep-impacted sector show that a significant number of native and endemic herb and shrub species exhibit sympatric distribution patterns with introduced plants. Only one alien plant species has been recorded from any undisturbed and sheep-free island sector so far. Socorro Island provides support for the hypothesis that disturbance of a pristine ecosystem is generally required for the colonization and naturalization of alien plants. Sheep are also indirectly responsible for the self-invasion of mainland bird species into novel island habitats and for the decline and range contraction of several endemic bird species. [ABSTRACT FROM AUTHOR]

We genetically analysed cordgrass plants and seedlings throughout the San Francisco, California, USA, estuary and found that hybrids between exotic Spartina alterniflora and native Spartina foliosa are the principal cordgrass invaders and colonizers. We hypothesized that this was due to higher seed set and siring ability by hybrids relative to the native species; too few alien parents remained in San Francisco Bay for our comparative studies. Hybrid seed comprised 91% to 98% of that set in the marsh study plants over the 2 years of the study. Total viable pollen production by hybrid plants was 400 times that of the native plants. Seed and pollen production were highly skewed towards a few hybrid genotypes. In addition to seed produced by hybrid plants, hybrid seed was produced by S. foliosa due to hybrid backcrossing. While the greatest advantage for hybrids was in pollen and seed production, hybrid seeds germinated, and seedlings survived and grew as well or better than the native species. As native S. foliosa becomes increasingly rare, hybrid seed floating on the tides will predominate, overwhelming recruitment sites and resulting in further colonization by hybrids. In an evolutionary context, hybrids with exceptional pollen and seed production will be initially favoured by natural selection, leading to the evolution of even more fertile hybrid genotypes. [ABSTRACT FROM AUTHOR]

Dispersal is a significant determinant of the pattern and process of invasions; however, weed dispersal distances are rarely described and descriptions of dispersal kernels are completely lacking for vertebrate-dispersed weeds. Here, we describe dispersal kernels generated by a native disperser, the endangered southern cassowary ( Casuarius casuarius, L.) for an invasive, tropical rainforest plant, pond apple ( Annona glabra, L.). Pond apple is primarily water-dispersed and is managed as such. We consider whether cassowary dispersal, as a numerically subordinate dispersal mode, provides an additional dispersal service that may modify the invasion process. In infested areas, pond apple seed was common in cassowary dung. Gut passage had no effect on the probability of single seed germination but deposition in clumps or as whole fruits reduced the probability of germination below that of single seeds. Gut passage times ranged from 65 to 1675 min. Combined with cassowary movement data, this resulted in estimated dispersal distances of 12.5–5212 m, with a median distance of 387 m (quartile range 112–787 m). Native frugivores can be effective dispersers of weeds in rainforest and even terrestrial dispersers can provide long-distance dispersal. Importantly, though pond apple might be expected to be almost entirely dispersed downstream and along the margins of aquatic and marine habitats, cassowaries provide dispersal upstream and between drainages, leading to novel dispersal outcomes. Even through the provision of small quantities of novel dispersal outcomes, subordinate dispersal modes can play a significant role in determining invasion pattern and influence the ultimate success of control programs by providing dispersal to locations unattainable via the primary mode. [ABSTRACT FROM AUTHOR]

International trade in horticultural plants is a major pathway of introduction of invasive species. Pampas grass ( Cortaderia selloana) is an invasive species of horticultural origin that is native to South America but cultivated as an ornamental in regions with Mediterranean climates worldwide. To gain insight into the introduction history of invasive populations in California, we analysed microsatellite marker variation in cultivated and invasive C. selloana. We sampled 275 cultivated plants from diverse sources and 698 invasive plants from 33 populations in four geographical regions of California. A model-based Bayesian clustering analysis identified seven distinct gene pools in cultivated C. selloana. Probabilities of assignment of invasive individuals to cultivated gene pools indicated that two gene pools accounted for the genomic origin of 78% of the invasive C. selloana sampled. Extensive admixture between cultivated source gene pools was detected within invasive individuals. Sources of admixed invasive individuals are probably landscape plantings. Consistent with the Bayesian assignment results indicating that multiple cultivated gene pools and landscape plantings are probable sources of invasive populations, FST and neighbour-joining clustering analyses indicated multiple escapes from shared sources in each geographical region. No isolation by distance or geographical trend in reduction of genetic diversity was evident. Furthermore, a generally random and discontinuous distribution of proportional assignments of invasive populations to cultivated gene pools suggests that introductions occurred recurrently within each geographical region. Our results strongly suggest that dispersal through local landscape plantings has contributed to the range expansion of invasive C. selloana in California. [ABSTRACT FROM AUTHOR]

The article provides a review of the status of invasive alien ornamental plants in mountain forests of Réunion, the last of the Mascarene Archipelago with large areas of untransformed mountain forests. Fourteen ornamental species have been identified as highly invasive in the Réunion mountain forests. To address the threat posed by alien species to native forests, the Office National des Forêts (ONF) and local partners have developed and implemented an early detection and monitoring program. Proposed management efforts include educating urban residents about native species and invasive ornamental species, involving the cooperation of landowners surrounding buffer zones, and promoting early detection activities.

We describe a model to predict the invasion success of alien plants on Mediterranean islands, according to their mode, frequency and time since introduction and simple species traits. The model was developed using canonical discriminant analysis to identify categories of low- and high-risk species. Whilst classifying ca 80% of the data set correctly, the type II error rate remained moderately high, which limits its value in practical terms. This level of accuracy is typical of similar models, and critical analysis of the weaknesses is necessary to develop long-term improvements in methodology. Sensitivity analysis indicates that, overall, mode of introduction had an important influence on invasiveness, with species introduced for public amenity being more likely to attain high-risk status than species introduced privately to gardens. Frequency and time since introduction had a relatively minor influence on the model outcome, but remained highly confounded with other variables. Although invasion success, as measured by the number of islands colonized, is expected to increase over time, it was not possible to estimate the rates of expansion from historical trends, which are complicated by changes in import fashions over the centuries. Many older introductions were crops, whereas there has been a recent tendency towards exotic ornamentals and weedy species. Despite a fundamental influence on the results, similar historical influences are seldom taken into account adequately during trait analyses. Unravelling such inter-correlations between predictors is therefore an important challenge for the future of screening protocols. [ABSTRACT FROM AUTHOR]

1. Some of the most damaging invasive plants are dispersed by frugivores and this is an area of emerging importance in weed management. It highlights the need for practical information on how frugivores affect weed population dynamics and spread, how frugivore populations are affected by weeds and what management recommendations are available. 2. Fruit traits influence frugivore choice. Fruit size, the presence of an inedible peel, defensive chemistry, crop size and phenology may all be useful traits for consideration in screening and eradication programmes. By considering the effect of these traits on the probability, quality and quantity of seed dispersal, it may be possible to rank invasive species by their desirability to frugivores. Fruit traits can also be manipulated with biocontrol agents. 3. Functional groups of frugivores can be assembled according to broad species groupings, and further refined according to size, gape size, pre- and post-ingestion processing techniques and movement patterns, to predict dispersal and establishment patterns for plant introductions. 4. Landscape fragmentation can increase frugivore dispersal of invasives, as many invasive plants and dispersers readily use disturbed matrix environments and fragment edges. Dispersal to particular landscape features, such as perches and edges, can be manipulated to function as seed sinks if control measures are concentrated in these areas. 5. Where invasive plants comprise part of the diet of native frugivores, there may be a conservation conflict between control of the invasive and maintaining populations of the native frugivore, especially where other threats such as habitat destruction have reduced populations of native fruit species. 6. Synthesis and applications. Development of functional groups of frugivore-dispersed invasive plants and dispersers will enable us to develop predictions for novel dispersal interactions at both population and community scales. Increasingly sophisticated mechanistic seed dispersal models combined with spatially explicit simulations show much promise for providing weed managers with the information they need to develop strategies for surveying, eradicating and managing plant invasions. Possible conservation conflicts mean that understanding the nature of the invasive plant–frugivore interaction is essential for determining appropriate management. [ABSTRACT FROM AUTHOR]

The article discusses the factors in the successful invasion of Rhododendron ponticum in Great Britain and Ireland. Rhododendron is considered as the most expensive alien plant conservation problem in the two countries because of human action. The biological characteristics of the plant, particularly its ease of propagation, had matched both the needs for a successful product in the horticultural market. The study showed that social, economic and ecological factors had promoted the establishment and spread of plants introduced for horticultural reasons.

To assess the validity of previously developed risk assessment schemes in the conditions of Central Europe, we tested (1) Australian weed risk assessment scheme (WRA; Pheloung et al. 1999); (2) WRA with additional analysis by Daehler et al. (2004); and (3) decision tree scheme of Reichard and Hamilton (1997) developed in North America, on a data set of 180 alien woody species commonly planted in the Czech Republic. This list included 17 invasive species, 9 naturalized but non-invasive, 31 casual aliens, and 123 species not reported to escape from cultivation. The WRA model with additional analysis provided best results, rejecting 100% of invasive species, accepting 83.8% of non-invasive, and recommending further 13.0% for additional analysis. Overall accuracy of the WRA model with additional analysis was 85.5%, higher than that of the basic WRA scheme (67.9%) and the Reichard–Hamilton model (61.6%). Only the Reichard–Hamilton scheme accepted some invaders. The probability that an accepted species will become an invader was zero for both WRA models and 3.2% for the Reichard–Hamilton model. The probability that a rejected species would have been an invader was 77.3% for both WRA models and 24.0% for the Reichard–Hamilton model. It is concluded that the WRA model, especially with additional analysis, appears to be a promising template for building a widely applicable system for screening out invasive plant introductions. [ABSTRACT FROM AUTHOR]

Non-native plant species are common along roadsides, but presence does not necessarily indicate spread along the road axis. Roadsides may serve merely as habitat for a species spreading independently of roads. The potential conduit function of roads depends on the habitat specificity of the spreading species, its dispersal range relative to the spacing of roads in the landscape, and the relative importance of long- and short-range dispersal. We describe a demographic model of the road× species interaction and suggest methods of assessing conduit function in the field based on the model results. A species limited to roadside habitat will be constrained to spread along the road axis unless its long-range dispersal is sufficient to carry it across the intervening unfavorable area to another road. It will propagate along a road corridor at a rate determined by the scale of short-range dispersal. Effective management of an invasion requires distinguishing between the habitat and conduit functions, a distinction difficult to make with only snapshot data. Invasions can be reconstructed by several methods, but none is totally satisfactory. We suggest comparing stem distributions on transects parallel and perpendicular to the road axis, and beside the road, and away from it, with an idealized Gaussian curve. Such comparisons would allow discrimination between pattern determined by habitat suitability and pattern reflecting random and facilitated dispersal. [ABSTRACT FROM AUTHOR]

Based on the analysis of invasions of alien plants in Ukraine, the impact of non-native plant species upon the native flora and adverse consequences of their spread are assessed. A case study gives examples of the role of alien plants in fragmentation of populations of native species; contamination of genetic resources of rare and endangered native species, formation of new ecotypes and hybridization with native taxa, disruption of the structure of natural plant communities as a result of introduction of alien species and formation of specific plant communities with domination of aliens. Arguments are provided against uncontrolled casual introductions and subsequent escape from cultivation as a result of ill-judged deliberate introduction of plants for ornamental, agricultural, technical, forestry, and other uses without any preliminary assessment of their invasion potential in the region concerned. Invasions of alien plants promote dramatic changes in the taxonomic, geographical, and ecological patterns of local floras, disruptions in the phytosociological spectrum, spectra of biomorphs, deterioration of zonal peculiarities of the flora, and finally lead to the decline of the vegetation productivity. A list of highly invasive plant species threatening forest, steppe, and submediterranean zones of East Europe is provided. [ABSTRACT FROM AUTHOR]

Abstract: Disturbances favour plant invasions because they provide a pulse of resources for seedling establishment and growth. However, little attention has been paid to the importance of the different disturbance regimes in the extent of invasion. In this paper we asked to what extent invasion depends on spatial and temporal patterns of disturbance. By using the spatially explicit model Fateland, we simulated how Cortaderia selloana, a large-wind dispersed perennial grass invading Mediterranean grasslands, responds to different medium-term (up to 55 years) disturbance regimes. The different scenarios combine disturbance frequency, extent of disturbance and temporal and spatial disturbance variability, and they roughly mimic real situations of habitat management and disturbances in cultural landscapes. The model predicted that the proportion of invaded area would increase with disturbance frequency. The extent of the disturbance overcame the importance of frequency. Aggregated disturbances randomly distributed in space had a more positive effect on invasion than scattered disturbances at repeatedly fixed locations. Whether the disturbances regularly occurred in time or were irregularly distributed did not influence the percentage of invaded landscape. Our simulation analysis unambiguously supports the hypothesis that disturbances are essential for the persistence and expansion of Cortaderia sellona. The high amount of seed rain from a few individuals (e.g., gardens) make this species very sensitive to landscape changes produced by different disturbance patterns (e.g., land abandonment, habitat management or rubbish dumping). Our results can contribute to redirect land management options. [Copyright &y& Elsevier]

• Background and Aims The long-lived and mainly outcrossing species Sarracenia purpurea has been introduced into Switzerland and become invasive. This creates the opportunity to study reactions to founder effect and how a species can circumvent deleterious effects of bottlenecks such as reduced genetic diversity, inbreeding and extinction through mutational meltdown, to emerge as a highly invasive plant.• Methods A population genetic survey by random amplified polymorphism DNA markers (RAPD) together with historical insights and a field pollination experiment were carried out.• Key Results At the regional scale, S. purpurea shows low structure (θst = 0·072) due to a recent founder event and important subsequent growth. Nevertheless, multivariate statistical analyses reveal that, because of a bottleneck that shifted allele frequencies, most of the variability is independent among populations. In one population (Tenasses) the species has become invasive and genetic analysis reveals restricted gene flow and family structure (θst = 0·287). Although inbreeding appears to be high (Fis > 0·410 from a Bayesian estimation), a field pollination experiment failed to detect significant inbreeding depression upon F1 seed number and seed weight fitness-traits. Furthermore, crosses between unrelated individuals produced F1 seeds with significantly reduced fitness, thus showing local outbreeding depression.• Conclusions The results suggest that, under restricted gene flow among families, the species may not only have rapidly purged deleterious alleles, but also have undergone some form of selection for inbreeding due to co-adaptation between loci. [ABSTRACT FROM AUTHOR]

Integrated control aimed at reducing impacts of alien woody plant invasions on biodiversity is underway in many parts of the Cape Floristic Region. However, the kinds of control measures applied may themselves affect the recovery of the natural vegetation. In view of this, we investigated the effects of past management practices, viz: ‘bulldozing and aerial-spraying’, ‘aerial-spraying’, ‘boom-spraying’ and ‘foliar-spraying’ aimed at clearing invasive alien woody plants on subsequent fynbos recovery in the Table Mountain National Park. Changes in soil (pH and depth) and vegetation (species cover, richness, diversity, evenness) properties, the total cover of species representing different dispersal guild, regenerative mode, and life form categories were compared between the differently treated and control plots at three different sites in the reserve. Only partial recovery of fynbos was observed in the ‘boom-sprayed’ and one of the ‘foliar-sprayed’ plots where measured species richness was significantly lower than that in control plots. However, marked changes in community structure were observed following ‘boom-spraying’ and ‘foliar-spraying’ at one site where a significant reduction in long-lived obligate reseeding species and an increase in the graminoid component was measured, though high fuel loads with possible post-fire erosion may also have aggravated the effects of foliar-spraying. Growth form structure changed the least following ‘aerial-spray- ing’ and ‘foliar-spraying’. Multivariate analysis of plant functional types indicated a greater similarity between the control plots than the differently treated plots, imply- ing a treatment effect on subsequent fynbos recovery. However, past land use and residual effects of the alien woody invaders may also have contributed to the differential recovery in the treated plots. It is concluded that re-introduction of species in the under-represented guilds may speed up fynbos recovery. The recommendation is a comprehensive seed mix containing the major guilds, and an initial seed mix of fast-growing indigenous species to stabilise the soil. [ABSTRACT FROM AUTHOR]

Ligustrum sinense (Oleaceae) is an invasive shrub in the southeastern United States that was introduced from China. In middle Tennessee, the species grows with Forestiera ligustrina (Oleaceae), a shrub native to the southeastern United States, in the redcedar and/or hardwood forests surrounding cedar (limestone) glades. Here we compare the growth and reproduction of the two species and identify attributes that might influence the invasiveness and persistence of L. sinense. Plants of both species were sampled along the woodland edges of cedar glades and in the (primarily) redcedar forest at Stones River National Battlefield, Rutherford County, Tennessee, between March 2000 and February 2001. MANOVAs (P ≤ 0.05) indicated significant differences between species and habitats for several of the 23 traits measured in the study. Regardless of the habitat, L. sinense had a more treelike growth form—higher leaf area ratio (leafiness), leaf mass ratio (investment in leaf biomass), stem elongation rate, and number of fruits per ramet—and a lower percentage of insect-damaged leaves and leaf abscission rate than F. ligustrina. Height and leaf areas of L. sinense plants growing in the woods were greater than those of L. sinense plants growing along the glade and greater than those of F. ligustrina plants growing in both habitats. Branch architecture did not differ appreciably between the species. Ligustrum sinense appears to possess a competitive advantage over F. ligustrina because of its greater ability to spatially and temporally capture light, a phenomenon that may lead to higher photosynthetic capacity and resource-use efficiency, and because of the higher fruit production we observed. [ABSTRACT FROM AUTHOR]

The authors comment on nonnative plant introductions and the ecological impacts of plant invasions. According to the authors, there is a need to examine the shifting dynamics and ecological effects of plant invasions. Topics discussed include factors influencing the effects of invasive plants, ecological succession, and the need for mechanistic evaluations of invasion dynamics and effects.