Crested floating heart [Nymphoides cristata (Roxb.) Kuntze] is an invasive aquatic plant in the southeastern United States. For clonal plants like N. cristata, clonal diversity may influence response to control tactics and/or evolutionary potential. However, little is known about the diversity of introduced N. cristata. In this study, we used genotyping-by-sequencing to quantify N. cristata diversity in the southeastern U.S. and determine how that diversity is distributed across the invaded range. Our results show that at least three distinct genetic lineages of N. cristata are present in the southeastern U.S. Geographic distribution of the lineages varied, with one widespread lineage identified across several states and others only found in a single waterbody. There is also evidence of extensive asexual reproduction, with invaded waterbodies often host to a single genetic lineage. The genetic diversity reported in this study likely results from multiple introductions of N. cristata to the southeastern U.S. and should be considered by managers when assessing control tactics such as screening for biocontrol agents or herbicide testing. The extent and distribution of genetic diversity should also be considered by researchers studying the potential for invasive spread of N. cristata within the U.S. or hybridization with native Nymphoides species.

Invasive species can have disastrous effects on the ecosystems they invade, requiring costly, labour-intensive mitigation. Public awareness campaigns are often used as a tool to reduce these species’ impacts. While heralded as useful and cost-effective, little evidence suggests that these campaigns contribute to meaningful biological outcomes. Furthermore, awareness campaigns are relatively understudied despite their usage as a common approach to mitigating invasive species. We conducted a literature review to assess publications that evaluated the efficacy of public awareness campaigns for managing invasive species. Out of 4382 papers initially extracted for analysis, we determined that 24 of them included studies conducted on awareness campaigns for invasive species. Four public awareness campaigns were deemed a ‘success’, and the other campaigns’ success was indeterminable due to study design. Our study revealed that inconsistencies in defined end points, unclear procedures and variability of campaigns contribute to there being insufficient evidence to determine the efficacy of public awareness campaigns. To evaluate the true efficacy of public awareness campaigns, we recommend that organizations conducting such campaigns implement rigorous and standardized assessments (e.g., Before–After Control–Impact designs or Bayesian analyses) that include measures of not just changes in the knowledge and behaviour of target audiences, but also relevant biological outcomes.

The family Solanaceae lists about 1,400 species worldwide, of which 143 are considered weeds (Sheppard et al. 2006). The genus Solanum is the most numerous of the family Solanaceae. Solanum elaeagnifolium Cav. belongs to the clade Leptostemonum, commonly known as the “spiny solanum” clade. Solanum elaeagnifolium is native to northern Mexico and the American Southwest. A revision for the S. elaeagnifolium clade and analytic phytokeys are provided by Knapp et al. (2017). The silvery color of its leaves and their resemblance to the leaves of the olive tree (Elaeagnus) were the reasons for naming the species elaeagnifolium (Heap and Carter 1999). Nowadays, it is commonly known as silverleaf nightshade (Boyd et al. 1984). According to Krigas et al. (2021), in northern Greece S. elaeagnifolium is also called “Lernaean Hydra,” due to its intense regrowth after herbicide treatment. Solanum elaeagnifolium is known in South Africa as silverleaf bitter apple or Satansbos (Satan’s bush), indicating how harmful it is to the country (Wilson et al. 2013). In America and other parts of the world, it has received various names over the years, such as white horsenettle, bullnettle, tomatillo, meloncillo, and trompillo (Davis et al. 1945; Kwong et al. 2006). In Algeria, farmers call it echouka, which means thorn, because of the multiple spines on the stem (Adjim and Kazi Tani 2018). In South Korea, it received the name Eun-bit-kka-ma-jung, which is a combination of its silvery coloration and a common plant in the country (Hong et al. 2014).

To gain insights into the trichurid diversity in pre-Hispanic remains of South American camelids (SACs), as well as into modern SAC populations, a bibliographic search was carried out to find parasitological studies. Results showed that a total of 17 studies were performed at archaeological and paleontological sites, in which a total of 213 samples were examined. The sample set was used as the unit of analysis, and 83% of 52 pre-Hispanic sample sets were positive for parasites. Parasitological studies confirmed the pre-Hispanic presence of diverse trichurids: two Trichuris species and capillariid eggs with morphological differences that allowed them to be assigned to three different species. Currently, the richness of the native trichurid assemblages in SACs has been extended by the inclusion of two species (Trichuris sp. 2 and Capillariinae gen. sp. 1). Modern T. tenuis Chandler, 1930, considered SAC-specific, would have invaded SAC populations during the European colonization. The estimate of regional and temporal trichurid prevalence and paleoecological information allowed us to propose a possible origin for some of them. Although the present analysis is exploratory, it should stimulate future studies about the biogeographic history of SAC helminths, provide relevant information to improve descriptions of the Holocene ecology, and identify threatened helminths.

Deciding whether or not eradication of an invasive species has been successful is one of the main dilemmas facing managers of eradication programmes. When the species is no longer being detected, a decision must be made about when to stop the eradication programme and declare success. In practice, this decision is usually based on ad hoc rules, which may be inefficient. Since surveillance undertaken to confirm species absence is imperfect, any declaration of eradication success must consider the risk and the consequences of being wrong. If surveillance is insufficient, then eradication may be falsely declared (a Type I error), whereas continuation of surveillance when eradication has already occurred wastes resources (a Type II error). We review the various methods that have been developed for quantifying these errors and incorporating them into the decision-making process. We conclude with an overview of future developments likely to improve the practice of determining invasive species eradication success.

Biological invasions represent one of the main threats to biodiversity and a recognized economic burden worldwide; the issue has been included in the conservation agenda such as the Convention on Biological Diversity (CBD). Brazil is a signatory country of the CBD; however, the number of alien species records in its territory is continuously rising. To evaluate the invasive alien species (IAS) policy in Brazil, we reviewed the legislation delineating historical trends to identify potential gaps and avenues for improvement. We consulted several websites using keywords related to invasions in order to track legal instruments such as laws, decrees and regulations. We classified the documents regarding their main aims with regard to IAS, taxon and environment of interest. We found 85 legal instruments in force related to IAS published in the federal sphere up to October 2021, with decrees being the most common type. Most documents were classified as ‘control’ and ‘prevention’ and were related to all taxa and environments. Two species (wild boar Sus scrofa and golden mussel Limnoperna fortunei) have more specific legislation, probably due to their conspicuous economic impacts. We discuss policy gaps and their implications for the efficient management and prevention of new IAS introductions to the country.

Invasive predators can have wide-ranging effects on invaded ecosystems and identifying the prey spectra and preferences of invaders are important steps in assessing their potential impacts on native biota. In this study, we investigated prey preferences of two invasive crab species (Hemigrapsus sanguineus and Hemigrapsus takanoi) that recently invaded Europe's shores and compared them with preferences of native shore crabs (Carcinus maenas) of similar size. In laboratory experiments, all three crab species preferred animal over algal prey. In general, sessile mussels (Mytilus edulis) were preferred over motile amphipods (Gammarus locusta) by all three crab species but amphipod predation was lower in the invasive compared with the native crabs. For the two invasive crab species, this pattern was the same in treatments where prey was offered separately (no-choice treatments) or simultaneously (choice treatments), while for the native crabs, mussel preference disappeared in choice treatments. The general preference of mussels by all three crab species suggests that local invasions of crabs most likely lead to increased competition among crabs. In addition, given that local densities of invasive crabs are often much higher than those of native crabs, predation pressure on native mussels can be expected to strongly increase at invaded sites. In contrast, local predation pressure on amphipods may be less affected by the crab invasions. Further field studies are needed to establish the magnitude of competition and predation pressure exerted by the invaders under natural conditions.

In a fast-changing and globalized world, parasites are moved across continents at an increasing pace. Co-invasion of parasites and their hosts is leading to the emergence of infectious diseases at a global scale, underlining the need for integration of biological invasions and disease ecology research. In this review, the ecological and evolutionary factors influencing the invasion process of parasites with complex life cycles were analysed, using the invasion of the European strain of Echinococcus multilocularis in North America as a model. The aim was to propose an ecological framework for investigating the invasion of parasites that are trophically transmitted through predator–prey interactions, showing how despite the complexity of the cycles and the interactions among multiple hosts, such parasites can overcome multiple barriers and become invasive. Identifying the key ecological processes affecting the success of parasite invasions is an important step for risk assessment and development of management strategies, particularly for parasites with the potential to infect people (i.e. zoonotic).

The negative effects of invasive plant species on native ecosystems, which can be large and long-lasting, are the primary justifications for their research and management. Tremendous effort is focused on quantifying the ecological impacts of invasive plants, though two different methods are primarily used: observational (compare invaded and uninvaded) and removals (compare invaded and invader removal). However, it is unknown whether these methods, which differ in their assumptions and execution, yield similar results, which could affect our ability to draw broad conclusions within and across studies. Therefore, we performed a meta-analysis on 174 studies that described 547 impacts of 72 invasive plants to test the effect of study method, invader cover, and removal period on the direction and magnitude of impact. Overall, by only considering impact magnitude and not direction, both observational and removal methods yielded similar results—invasive plants are changing most aspects of the ecosystem—and the variation among species and study systems was dramatically reduced compared with traditional, directionally focused studies. This is contrary to a similar analysis that did not control for directionality of impacts, which found overall differences in impact depended on methodology. However, even when the effects of study ecosystem, invader life-form, and impact type were accounted for, significant differences occurred between removal and observational studies. Particularly vulnerable systems appear to be those that would be more greatly disturbed by the removal of the target species, such as tree species or invasive plants in riparian areas. Additionally, impact magnitude increased with invader cover and removal time. We confirm that invasive plants impact the systems they invade in a nonuniform manner; however, we suggest some study conditions may be more sensitive to study methodology. Careful consideration should be given as to which methodology is used in the context of the study system.

The invasive sabellid Branchiomma bairdi (McIntosh, 1885) was collected in the Estany des Peix lagoon (Formentera Island, Balearic Sea, Western Mediterranean). This species is native to Bermuda (Western Atlantic Ocean), being widely distributed through the Caribbean Sea. However, it has been described as invasive worldwide, being also present in the Indo-Pacific region, the Eastern Atlantic Ocean and the Mediterranean Sea. We here provide the first record of the species for the Balearic Sea, together with a comparison to other morphologically similar alien species, Branchiomma boholense (Grube, 1878), which is supposed to have also been introduced in the Mediterranean basin. We also include comprehensive taxonomic descriptions of both taxa based on the type material, a dichotomous key for the Mediterranean species of Branchiomma and hypothesize the most likely way of introduction of B. bairdi in the Balearic region.

Croftonweed is an invasive plant in southwest China. We examined the relationships between its invasion patterns and native plant diversity at different spatio-temporal scales. At the 25 m2 scale, invasion success was negatively correlated with native plant diversity, indicating that resource availability might be the dominant factor regulating community invasibility. At the 400-m2 scale, both negative and positive relationships were detected, possibly identifying a spatial scale threshold where extrinsic environmental factors became more important to community invasibility. At the vegetation province scale, variations in physical environment outweighed the importance of intrinsic biotic factors and positive relationships between diversity and invader success were found. Native plant diversity also inhibited croftonweed over the course of community succession and at the early stages of invasion at local spatial scales. However, the changing relationship might be an artifact of sampling at different spatial scales.

Large-statured invasive grasses (LSIGs) constitute a distinct functional group with characteristic life history traits that facilitate colonization and aggressive growth in aquatic ecosystems, particularly those modified by human activities. These species typically form monocultures in the systems they invade and have wide-ranging and negative impacts on biodiversity and ecosystem processes. In March 2008, a special symposium was held as part of the Western Society of Weed Scientists annual meeting to synthesize our current knowledge of the ecological impacts and management of two notorious LSIGs: Arundo donax and Phragmites australis. In this volume of Invasive Plant Science and Management, symposium participants provide articles summarizing existing knowledge, recent research progress, and research needs for these two taxa. Here, we summarize the basic biology of these species and suggest the use of a more holistic approach to deal with the effects and management of LSIG invasions.

The presence of landscape disturbances increases the establishment of exotic plants inside natural areas. Here, we examine the effect of human disturbances to prairie landscapes on the distribution and abundance of Kentucky bluegrass and smooth brome, exotic grasses that threaten the integrity of prairie ecosystems throughout the northern Great Plains. Using plant inventory data from Riding Mountain National Park in Manitoba, Canada, we investigated how roads, trails, and the intensity of historic livestock grazing affect the distribution and abundance of exotic grasses. On the basis of our results, both Kentucky bluegrass and smooth brome were more abundant in areas closer to roads. Kentucky bluegrass was also more abundant in areas farther from trails and those historically grazed by cattle. Our research demonstrates that the effect of landscape disturbances on exotic grasses varies between species and suggests that patterns of invasion may reflect different introduction histories. Given our findings, conserving the integrity of northern fescue prairies should account for human disturbances of landscapes and their effects on the proliferation of exotic plants into areas of native prairie.

Chinese and European privets are among the most aggressive invasive shrubs in forestlands of the southern United States. We analyzed extensive field data collected by the U.S. Forest Service covering 12 states to identify potential determinants of invasion and to predict likelihood of further invasion under a variety of possible management strategies. Results of multiple logistic regression, which classified 75% of the field plots correctly with regard to species presence and absence, indicated probability of invasion is correlated positively with elevation, adjacency (within 300 m) to waterbodies, mean extreme maximum temperature, site productivity, species diversity, natural regeneration, wind disturbance, animal disturbance, and private land ownership and is correlated negatively with slope, stand age, site preparation, artificial regeneration, distance to the nearest road, fire disturbance, and public land ownership. Habitats most at risk to further invasion (likelihood of invasion > 10%) under current conditions occur throughout Mississippi, with a band stretching eastward across south-central Alabama, and in eastern Texas and western Louisiana. Invasion likelihoods could be reduced most by conversion to public land ownership, followed by site preparation, fire disturbance, artificial regeneration, and elimination of animal disturbance. While conversion of land ownership may be neither feasible nor desirable, this result emphasizes the opportunity for reducing the likelihood of invasions on private lands via increased use of selected management practices.

Establishment potential is one of the primary components of invasive species risk assessment. Models that predict establishment of potentially invasive ornamental crops often ignore differences among cultivars and the variability in plant response to site-specific factors. The objective of this study was to determine the extent to which differences among cultivars and habitat characteristics affect establishment of 5 cultivars of ornamental cleome. Experiments were conducted to compare germination, survival, and growth of cultivars in cultivated (gardens) and noncultivated (roadsides and prairies) environments and, in prairies, the effects of competition (low, intermediate, and high). In the first experiment, germination, survival, and growth were recorded in gardens, prairies, and roadsides in four locations in Minnesota. In the second experiment, the effects of competition with resident species were studied in five seed lots from three cultivars in three prairie sites. Additionally, a quantitative description of germination and transplantable seedling quality, when grown under greenhouse production standards, was obtained and compared with results from the cultivated and noncultivated outdoor environments. Germination in greenhouse conditions was significantly greater (78%) than in garden, prairies, or roadsides (< 46%). Mortality was greater in noncultivated than in cultivated environments (3% wk−1 and 1.4% wk−1, respectively). Survival was affected by competition, which reduced population establishment. Cultivar differences were most pronounced at seedling emergence, whereas habitat characteristics were more influential at later stages of the life cycle. Germination and plant height were similar among noncultivated environments. Variability in seedling emergence, survival, and growth in response to cultivar, habitat, and competition are important determinants of establishment potential. Among the cultivars studied, the native cleome, roughseed clammyweed, has a greater establishment potential than the nonnative cleome, spiderflower.

The rate of transportation, introduction, dissemination, and spread of nonnative species is increasing despite growing global awareness of the extent and impact of biological invasions. Effective policies are needed to prevent an increase in the significant negative environmental and economic impacts caused by invasive species. Here we explore this issue in the context of the history of invasion and subsequent regulation of cacti introduced to South Africa. We consider seven approaches to restricting trade by banning the following: (1) species already invasive in the region, (2) species invasive anywhere in the world, (3) species invasive anywhere in the world with a climate similar to the target region, (4) genera containing invasive species, (5) growth forms associated with invasiveness, (6) cacti with seed characteristics associated with invasiveness, and (7) the whole family. We evaluate each approach on the basis of the availability and complexity of information required for implementation, including the cost of the research needed to acquire such information, the likely numbers of false positives and false negatives, the likely degree of public acceptance, and the costs of implementation. Following a consultative process, we provide recommendations for how to regulate nonnative cacti in South Africa. The simplest option would be to ban all cacti, but available evidence suggests that most species pose negligible risk of becoming invasive, making this option unreasonable. The other extreme—reactively regulating species once they are invasive—would incur significant control costs, likely result in significant environmental and economic impacts, and limit management goals (e.g., eradication might be unfeasible). We recommended an intermediate option—the banning of all genera containing invasive species. This recommendation has been partly incorporated in South African regulations. Our study emphasizes the importance of scientific research, a legal framework, and participation of stakeholders in assessments. This approach builds awareness, trust, and support, and ensures that all interests are reflected in final regulations, making them easier to implement and enforce.

The importance of dispersal in the establishment and proliferation of exotic populations make this life history stage critical in the prediction and management of biological invasions. We observed the dispersal of seeds by patches of smooth brome invading northern fescue prairies and applied an inverse power function model to explore its potential invasion patterns. Based on our observations of two northern fescue prairies in Riding Mountain National Park, Manitoba, Canada, patterns of potential invasion were contingent upon the dispersal of seeds as individual florets or aggregated within spikelets and panicles. For example, although the majority of dispersed seeds were intercepted within one meter, inside and outside the margins of invading patches, slopes of the log–log plots of seed number against their dispersal distance were steeper for seeds dispersed as spikelets than individual florets. Despite the observed aggregation of seeds along the margins of invading patches, the number of dispersed seeds was poorly correlated with that germinated from the seed bank. The shallow dispersal gradient of individual florets and spikelets, combined with the steeper gradient of panicles suggest that smooth brome is capable of simultaneously invading along dense fronts and by establishing isolated foci. Although low correlations between the number of dispersed seeds and their recruitment from the seed bank might suggest postdispersal transport of seeds, other mechanisms, including seed predation and pathogens, remain unexplored. Conservation and restoration of northern fescue prairies must include efforts to control the dispersal of smooth brome seeds and reduce opportunities for their establishment.

The presence of introduced hosts can increase or decrease infections of co-introduced parasites in native species of conservation concern. In this study, we compared parasite abundance, intensity, and prevalence between native Awaous stamineus and introduced poeciliid fishes by a co-introduced nematode parasite (Camallanus cotti) in 42 watersheds across the Hawaiian Islands. We found that parasite abundance, intensity and prevalence were greater in native than introduced hosts. Parasite abundance, intensity and prevalence within A. stamineus varied between years, which largely reflected a transient spike in infection in three remote watersheds on Molokai. At each site we measured host factors (length, density of native host, density of introduced host) and environmental factors (per cent agricultural and urban land use, water chemistry, watershed area and precipitation) hypothesized to influence C. cotti abundance, intensity and prevalence. Factors associated with parasitism differed between native and introduced hosts. Notably, parasitism of native hosts was higher in streams with lower water quality, whereas parasitism of introduced hosts was lower in streams with lower water quality. We also found that parasite burdens were lower in both native and introduced hosts when coincident. Evidence of a mutual dilution effect indicates that introduced hosts can ameliorate parasitism of native fishes by co-introduced parasites, which raises questions about the value of remediation actions, such as the removal of introduced hosts, in stemming the rise of infectious disease in species of conservation concern.

Introduction of species is a major driver of global change and loss of biodiversity in ecosystems. The Mediterranean Sea is the most heavily invaded region in the world by introduced seaweeds. The fan mussel Pinna nobilis is the largest Mediterranean bivalve, and a protected species, present at depths from 0.5 m to 60 m. In Cabrera National Park marine protected area (MPA) (Balearic Islands, north-western Mediterranean) the population of P. nobilis is affected by the invasive seaweeds Lophocladia lallemandii and Caulerpa racemosa; however the extent of this colonization on the bivalve is unknown. Therefore, the main aims of the present study were to: (1) determine the extent of invasion of L. lallemandii and C. racemosa on the P. nobilis population; and (2) test if this invasion showed differences with depth. This is the first study assessing invasion by seaweeds on a large bivalve in a high density P. nobilis population. Pinna nobilis was distributed in all seagrass meadows surveyed within the MPA; we found a total of 872 live P. nobilis individuals, 449 and 423 of which were found at 10 and 20 m depth, respectively. High cover of L. lallemandii and low presence of C. racemosa were detected in the P. nobilis population, being quantified in 49.37% and 1.38% of the population of P. nobilis, respectively. Bathymetric differences on Lophocladia epizoism over P. nobilis has been recorded in this study; with increasing values of L. lallemandii cover index, biomass and volume at deeper depths. Pinna nobilis could be a preferential substratum for L. lallemandii in Posidonia oceanica meadows in deeper waters, acting as a stepping-stone for invasive seaweeds and facilitating the invasion throughout seagrass meadows.

Ants are among the worst invasive species, and can have tremendous negative impacts on native biodiversity, agriculture, estates, property and human health. Invasive ants are extremely difficult to control, and thus early detection is essential to prevent ant invasions, in particular through surveillance efforts at ports of entry. This paper assesses the potential distribution of 14 of the worst invasive ant species in France, under current and future climatic conditions. Consensus species distribution models, using five different modelling techniques, three global climate models and two CO2 emission scenarios, indicated that France presented suitable areas for 10/14 species, including five listed on the Invasive Species Specialist Group's selection of the world's 100 worst invasive species. Among these 10 species, eight were predicted to increase their potential range with climate change. Areas with the highest concentration of potential invaders were mainly located along the coastline, especially in the south-west of France, but all departments appeared to be climatically suitable for at least two invasive species. A ranking of climatic suitability per species for 17 major airports and 14 maritime ports indicated that the ports of entry with the highest suitability were located in Biarritz, Toulon and Nice, and the species with the greatest potential distribution in France were Lasius neglectus and Linepithema humile, followed by Solenopsis richteri, Pheidole megacephala and Wasmannia auropunctata.