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Aim: The Hemiptera is the fifth‐largest insect order but among non‐native insect species is approximately tied with the Coleoptera as the most species‐rich insect order (Hemiptera comprise 20% more species than in world fauna). This over‐representation may result from high propagule pressure or from high species invasiveness. Here, we assess the reasons for over‐representation in this group by analysing geographical, temporal and taxonomic variation in numbers of historical invasions. Location: Global. Method: We assembled lists of historical Hemiptera invasions in 12 world regions, countries or islands (Australia, Chile, Europe, New Zealand, North America, South Africa, South Korea, Japan and the Galapagos, Hawaiian, Okinawa and Ogasawara Islands) and border interception data from nine countries (Australia, Canada, European Union, United Kingdom, Hawaii, Japan, New Zealand, South Korea, USA mainland and South Africa). Using these data, we identified hemipteran superfamilies that are historically over‐represented among established non‐native species, and superfamilies that are over‐represented among arrivals (proxied by interceptions). We also compared temporal patterns of establishments among hemipteran suborders and among regions. Results: Across all regions, patterns of over‐ and under‐representation were similar. The Aphidoidea, Coccoidea, Aleyrodoidea, Cimicoidea and Phylloxeroida were over‐represented among non‐native species. These same superfamilies were not consistently over‐represented among intercepted species indicating that propagule pressure does not completely explain the tendency of some Hemiptera to be over‐represented among invasions. Asexual reproduction is common in most over‐represented superfamilies and this trait may be key to explaining high invasion success in these superfamilies. Conclusions: We conclude that both propagule pressure and species invasiveness are drivers of high invasion success in the Sternorrhyncha suborder (aphids, scales, whiteflies) and this group plays a major role in the exceptional invasion success of Hemiptera in general. The high historical rates of invasion by Sternorrhyncha species provide justification for biosecurity measure focusing on exclusion of this group. [ABSTRACT FROM AUTHOR]

Context: Non-native invasive plants are a growing threat to forests. Meanwhile, the amount of forest within the wildland-urban interface (WUI) is increasing, with housing-associated disturbances enabling the spread of non-native plants. Objectives: We tested whether (1) WUI or non-WUI forests are more invaded, (2) WUI intermix forests (houses mingling with forest) are more invaded than interface forests (housing abutting forest), (3) invasion in WUI forests is delayed (invasion debt) following housing development, and (4) WUI forest invasion is associated with land cover context (a proxy for disturbance and propagule pressure). Methods: We conducted statistical comparisons of plant invasion metrics using WUI status information intersected with ~ 45,000 forest inventory plots (collected ca. 2015). We evaluated potential drivers of invasion using an ensemble learning approach and adopted a mixed-effects modeling framework to assess relationships between drivers and invasion. Results: Our analyses revealed that the degree of invasion in WUI forest plots was significantly higher. We found evidence for invasion debt, including greater invasion of plots in the WUI longer. WUI interface forests were more invaded than intermix forests. Agricultural and developed land cover at medium to large scales (~ 66 − 5,300 hectares) were most highly associated with WUI forest invasion. Conclusions: These findings elucidate dynamic plant invasion patterns and processes occurring within the WUI. They underscore the importance of monitoring and managing forests that have recently entered the WUI, with an emphasis on sources of exotic plant propagules at relatively large scales, before the housing invasion debt comes due. [ABSTRACT FROM AUTHOR]

Copyright of Biological Invasions is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of potentially beneficial microorganisms in agriculture (microbial inoculants) has rapidly accelerated in recent years. For microbial inoculants to be effective as agricultural tools, these organisms must be able to survive and persist in novel environments while not destabilizing the resident community or spilling over into adjacent natural ecosystems. Despite the importance of propagule pressure to species introductions, few tools exist in microbial ecology to predict the outcomes of agricultural microbial introductions. Here, we adapt a macroecological propagule pressure model to a microbial scale and present an experimental approach for testing the role of propagule pressure in microbial inoculant introductions. We experimentally determined the riskrelease relationship for an IAA-expressing Pseudomonas simiae inoculant in a model monocot system. We then used this relationship to simulate establishment outcomes under a range of application frequencies (propagule number) and inoculant concentrations (propagule size). Our simulations show that repeated inoculant applications may increase establishment, even when increased inoculant concentration does not alter establishment probabilities. Applying ecological modeling approaches like those presented here to microbial inoculants may aid their sustainable use and provide a monitoring tool for microbial inoculants. [ABSTRACT FROM AUTHOR]

In long‐distance dispersal events, colonising species typically begin with a small number of founding individuals. A growing body of research suggests that establishment success of small founding populations can be determined by the context of the colonisation event and the new environment. Here, we illuminate the importance of these sources of context dependence. Using a spatially explicit, temporally dynamic, mechanistic, individual‐based simulator of a model amphibian species, the cane toad (Rhinella marina), we simulated colonisation scenarios to investigate how (1) the number of founding individuals, (2) the number of dispersal events, (3) landscape's spatial composition and configuration of habitats ('spatially heterogeneous landscapes') and (4) the timing of arrival with regards to dynamic environmental conditions ('dynamic environmental conditions') influence the establishment success of small founding populations. We analysed the dynamic effects of these predictors on establishment success using running‐window logistic regression models. We showed establishment success increases with the number of founding individuals, whereas the number of dispersal events had a weak effect. At ≥ 20 founding individuals, propagule size swamps the effects of other factors, to whereby establishment success is near‐certain (≥ 90%). But below this level, confidence in establishment success dramatically decreases as number of founding individuals decreases. At low numbers of founding individuals, the prominent predictors are landscape spatial heterogeneity and dynamic environmental conditions. For instance, compared to the annual mean, founding populations with ≤ 5 individuals have up to 18% higher establishment success when they arrive in 'packed' landscapes with relatively limited and clustered essential habitats and right before the breeding season. Accounting for landscape spatial heterogeneity and dynamic environmental conditions is integral in understanding and predicting population establishment and species colonisation. This additional complexity is necessary for advancing biogeographical theory and its application, such as in guiding species reintroduction efforts and invasive alien species management. [ABSTRACT FROM AUTHOR]

Non-indigenous species (NIS) profoundly influence marine ecosystems globally. Our study examines NIS prevalence in Icelandic harbours, focusing on species richness and community composition of fouling species. Using settlement plates, we demonstrate NIS dominance, particularly of non-indigenous ascidians, aligning with global trends. The dominant species varied from year to year, likely influenced by environmental conditions, propagule pressure, and already established species. The escalation of maritime traffic, particularly in southwest Iceland, amplifies propagule pressure, thereby facilitating the establishment of NIS populations. Consequently, local maritime traffic can promote their further spread to other regional localities. Additionally, we documented three new bryozoan records for Iceland, highlighting the necessity for further biogeographic research. Cryptogenic species, comprising a notable portion of the fouling community, pose challenges to the understanding of biogeography and invasion ecology. Our findings emphasize the intricate dynamics of fouling communities in Icelandic harbours, underscoring the need for ongoing monitoring and management amidst environmental change and biological invasions. [ABSTRACT FROM AUTHOR]

Protected areas (PAs), particularly those in developing countries such as Nepal, are facing multiple anthropogenic threats including plant invasions. Despite the population-level recovery of some threatened wildlife species in Nepal’s PAs, their habitats have been degraded by invasive alien plants (IAPs). We quantified the threats of plant invasions in Nepal’s PAs by analyzing species checklists, propagule pressure, and climate suitability including potential invasion hotspots (i.e., the area with high potential vulnerability). Altogether 144 alien plant species have established in Nepal’s 20 PAs. They accounted > 10% of the total vascular plants in five PAs of southern lowlands. Seventeen PAs were invaded by 1–20 IAPs. Propagule pressure ranged from high to medium in 12 PAs with the highest level observed in a PA located near Nepal’s capital city. Nearly half of the PAs are at risk of being invaded by additional IAPs because they are climatically suitable for many IAPs already present in Nepal. Potential invasion hotspot accounted for > 50% of the total area in eight PAs; all but one of these PAs lie in southern lowlands. Overall, the results indicate that threat of plant invasions is higher to the southern lowland PAs than in the northern mountainous ones. Nevertheless, the risk of further invasions by additional IAPs is high in both lowland and highland PAs. Policy and management responses commensurate with the scale of plant invasion problems identified here will help achieve national PAs management objectives and consequently meet the global targets such as the Kunming-Montreal Global Biodiversity Framework Target 6. [ABSTRACT FROM AUTHOR]

Marine coastal habitats are often characterized by strong gradients of anthropogenic disturbance such as pollution, typically most severe at urban waterfronts. These variations create stress for local organisms leading to their distribution along the disturbance as a function of their tolerance. non-indigenous species (NIS) are considered more tolerant to anthropogenic disturbances than their native counterparts, thriving in urban areas, where native species are sparser. It is however not yet entirely clear if these distribution patterns are due to larval behavior and preferential settlement or post-settlement processes. In the present study, we investigated the abundance of adults and settlers of two native (Ostrea edulis, Mytilus galloprovincialis) and two non-indigenous (Magallana gigas, Xenostrobus securis) bivalves along a strong marine urban environmental gradient. Oysters had sparse abundances of both adults and settlers at all sites, with no obvious distributional gradients. The two mussel species showed different settler-adult distributions along the gradient. Both settlers and adults of the native mussel M. galloprovincialis strongly decreased moving from the outermost periurban site to the innermost urban site, consistent with preferential settlement of larvae according to environmental conditions. The non-indigenous adult mussel X. securis showed a distribution pattern opposite to that of M. galloprovincialis, markedly increasing in abundance from the outermost to the innermost site. This was not paralleled by the distribution of X. securis settlers, which established over a larger area, including sites where adults were essentially absent. The mismatch between settler and adult distributions for X. securis suggests that post-settlement factors dictate spatial adult distribution. [ABSTRACT FROM AUTHOR]

Introduction history, including propagule pressure and residence time, has been proposed as a primary driver of biological invasions. However, it is unclear whether introduction history increases the likelihood that a species will be invasive or only the likelihood that it will be established. Using a dataset of non‐native species historically available as ornamental plants in the conterminous United States, we investigated how introduction history relates to these stages of invasion. Introduction history was highly significant and a strong predictor of establishment, but only marginally significant and a poor predictor of invasive success. Propagule pressure predicted establishment better than residence time, with species likely to be established if they were introduced to only eight locations. These findings suggest that ongoing plant introductions will lead to widespread establishment but may not directly increase invasive success. Instead, other characteristics, like plant traits and local scale processes, may better predict whether a species becomes invasive. [ABSTRACT FROM AUTHOR]

Invasions are commonly found to benefit from disturbance events. However, the importance of the relative timing of the invasion and disturbance for invader success and impact on community composition remains uncertain. Here, we experimentally test this by invading a five‐species bacterial community on eight separate occasions—four before a disturbance and four after. Invader success and impact on community composition was greatest when the invasion immediately followed the disturbance. However, the subsequent invasions had negligible success or impact. Pre‐disturbance, invader success and impact was greatest when the invader was added just before the disturbance. Importantly, however, the first three pre‐disturbance invasion events had significantly greater success than the last three post‐disturbance invasions. Moreover, these findings were consistent across a range of propagule pressures. Overall, we demonstrate that timing is highly important for both the success and impact on community composition of an invader, with both being lower as time since disturbance progresses. [ABSTRACT FROM AUTHOR]

Biological invasions are a growing threat to biodiversity, food security, and economies. Rising pressure from increased global trade requires improving border inspection efficiency. Here, we depart from the conventional consignment‐by‐consignment approach advocated in current inspection standards. Instead, we suggest a broader perspective: evaluating border inspection regimes based on their ability to reduce propagule pressure across entire pathways. Additionally, we demonstrate that most biosecurity pathways exhibit superspreading behavior, that is, consignments from the same pathway have varying infestation rates and contain rare right‐tail events (also called overdispersion). We show that greater overdispersion leads to more pronounced diminishing returns, with consequences on the optimal allocation of sampling effort. We leverage these two insights to develop a simple and efficient border inspection regime that can significantly reduce propagule pressure compared to current standards. Our analysis revealed that consignment size is a key driver of biosecurity risk and that sampling proportional to the square root of consignment size is near optimal. In testing, our framework reduced propagule pressure by 31 to 38% compared to current standards. We also identified opportunities to further improve inspection efficiency by considering additional pathway characteristics (i.e., overdispersion parameters, zero inflation, relative risk, sampling cost, detectability) and developed solutions for these more complex scenarios. We anticipate our result will mitigate biological invasion risk with significant implications for biodiversity conservation, food security, and economies worldwide. [ABSTRACT FROM AUTHOR]

Roads are a widespread feature of anthropogenic landscapes, and roadsides serve as disturbed habitats suitable for ruderal plant species colonization. While roadside plant species are often exotic to a region, in some ecosystems such as the Florida scrub, roadsides are also home to numerous endemic, often imperiled species, that capitalize on open, disturbed habitat. Importantly, the co-occurrence of endemics and exotics along roadsides could threaten the populations of the endemics, yet it is unclear how frequently the two groups co-occur. Here, we conducted vegetation surveys across seven habitat types in the Florida scrub ecosystem to (1) examine the distribution and co-occurrence of scrub endemic and exotic species along sandy roadsides, and (2) determine the factors that best predict the occurrence of endemic and exotic species. We found that sandy roadsides were more frequently colonized by endemic rather than exotic plant species and that endemic and exotic species rarely co-occurred. Endemic species occurrence was best predicted by adjacent habitat type, while exotic species occurrence was best predicted by proximity to likely propagule sources. Overall, our study showed that scrub endemic and exotic species largely establish in distinct roadside areas. Our work informs our understanding of the role of roadside in species conservation as well as the potential role of biotic resistance against exotic species. [ABSTRACT FROM AUTHOR]

Biological invasions are one of the most important threats to biodiversity. However, spread mechanisms have been described in detail only for some widespread taxa. Here, we aim to characterize the unique phenomenon of × Sorbaronia ′Mitschurinii′ (Rosaceae) spread into temperate Scots pine forests. We assessed the surroundings of an abandoned × Sorbaronia ′Mitschurinii′ plantation, established in 1986 near Ośno Lubuskie (W Poland). Around the plantation we established 66 study plots in 30 m intervals along eight transects, in a systematic design. Using generalized linear mixed-effects models we analysed how the distance from the propagule source (i.e. abandoned plantation), maximum age of × Sorbaronia shrubs assessed using dendrochronological techniques, and light availability determined the density and biomass of the studied plant. We found that its mean aboveground biomass in the plantation was 7.22 ± 0.66 Mg ha−1, and decreased with distance from the propagule source: 6.83 Mg ha−1 30 m from the abandoned plantation, 1.38 Mg ha−1 at a distance of 90 m, and 0.11 Mg ha−1 at a distance of 180 m, almost disappearing at further distances (but present at the maximum distance of 450 m). The density and aboveground biomass of × Sorbaronia ′Mitschurinii′ increased with increasing maximal age of the studied plant and its light availability. The × Sorbaronia ′Mitschurinii′ plantation acted as a strong propagule source, as it reached a density of 100 ind. 100 m−2 after five years, forming a dense shrub layer, capable of reproducing. We conclude that alien species planted at high density and left with no management control might transform into invasion hotspots under favourable circumstances. The study highlights the importance of scientific awareness of similar cases of overlooked invasion sources, as management to limit their spread is still possible. [ABSTRACT FROM AUTHOR]

The use of potentially beneficial microorganisms in agriculture (microbial inoculants) has rapidly accelerated in recent years. For microbial inoculants to be effective as agricultural tools, these organisms must be able to survive and persist in novel environments while not destabilizing the resident community or spilling over into adjacent natural ecosystems. Despite the importance of propagule pressure to species introductions, few tools exist in microbial ecology to predict the outcomes of agricultural microbial introductions. Here, we adapt a macroecological propagule pressure model to a microbial scale and present an experimental approach for testing the role of propagule pressure in microbial inoculant introductions. We experimentally determined the risk-release relationship for an IAA-expressing Pseudomonas simiae inoculant in a model monocot system. We then used this relationship to simulate establishment outcomes under a range of application frequencies (propagule number) and inoculant concentrations (propagule size). Our simulations show that repeated inoculant applications may increase establishment, even when increased inoculant concentration does not alter establishment probabilities. Applying ecological modeling approaches like those presented here to microbial inoculants may aid their sustainable use and provide a monitoring tool for microbial inoculants.

Introduction: Freshwater ecosystems are susceptible to invasion by alien macrophytes due to their connectivity and various plant dispersal vectors. These ecosystems often experience anthropogenic nutrient enrichment, favouring invasive species that efficiently exploit these resources. Propagule pressure (reflecting the quantity of introduced individuals) and habitat invasibility are key determinants of invasion success. Moreover, the enemy release hypothesis predicts that escape from natural enemies, such as herbivores, allows alien species to invest more resources to growth and reproduction rather than defense, enhancing their invasive potential. Yet, the combined impact of propagule pressure, herbivory, and nutrient enrichment on the competitive dynamics between invasive alien macrophytes and native macrophyte communities is not well understood due to a paucity of studies. Methods: We conducted a full factorial mesocosm experiment to explore the individual and combined effects of herbivory, nutrient levels, propagule pressure, and competition on the invasion success of the alien macrophyte Myriophyllum aquaticum into a nativemacrophyte community comprising Vallisneria natans, Hydrilla verticillata, and Myriophyllum spicatum. This setup included varying M. aquaticum densities (low vs. high, simulating low and high propagule pressures), two levels of herbivory by the native snail Lymnaea stagnalis (herbivory vs no-herbivory), and two nutrient conditions (low vs. high). Myriophyllum aquaticum was also grown separately at both densities without competition from native macrophytes. Results: The invasive alien macrophyte M. aquaticum produced the highest shoot and total biomass when simultaneously subjected to conditions of high-density intraspecific competition, no herbivory, and low-nutrient availability treatments. Moreover, a high propagule pressure of M. aquaticum significantly reduced the growth of the native macrophyte community in nutrient-rich conditions, but this effect was not observed in nutrient-poor conditions. Discussion: These findings indicate that M. aquaticum has adaptive traits enabling it to flourish in the absence of herbivory (supporting the enemy release hypothesis) and in challenging environments such as intense intraspecific competition and low nutrient availability. Additionally, the findings demonstrate that when present in large numbers, M. aquaticum can significantly inhibit the growth of native macrophyte communities, particularly in nutrientrich environments. Consequently, reducing the propagule pressure of M. aquaticum could help control its spread and mitigate its ecological impact. Overall, these findings emphasize that the growth and impacts of invasive alien plants can vary across different habitat conditions and is shaped by the interplay of biotic and abiotic factors. [ABSTRACT FROM AUTHOR]

In response to non‐native plant invasions, many governments have established noxious weed lists to control and eradicate introduced invasive plants. However, invasive agronomic species are often unregulated, and the extent of their invasion across habitat types has never been determined.Using vegetation surveys across 222 plots, we investigated the contribution of agronomic versus noxious non‐native species to the levels of invasion across seven habitat types in central Canada.Although agronomic non‐native species, such as Poa pratensis and Bromus inermis, only made up 21.3% of the non‐native species pool, they accounted for 43.6% of non‐native plant species frequency and 74.4% of relative non‐native plant cover. They were also disproportionately overrepresented compared with noxious non‐native species across all habitat types, except saline marshes.The overabundance of agronomic non‐native plants in central Canada is likely the legacy of cultivar breeding, intentional seeding of introduced forage species and a lack of incentive for the use of native species.Synthesis and applications: Decelerating the invasion by agronomic non‐native plants will require approaches beyond noxious weed lists and initiatives in research, policy and education. These tools can include incentives to use native seed material, for example, in reclamation and forage and turf production, to reduce propagule pressure from invasive agronomic non‐native plants. [ABSTRACT FROM AUTHOR]

The conservation–invasion paradox (CIP) refers to a long‐term phenomenon wherein species threatened in their native range can sustain viable populations when introduced to other regions. Understanding the drivers of CIP is helpful for conserving threatened species and managing invasive species, which is unfortunately still lacking. We compiled a global data set of 1071 introduction events, including 960 CIP events (successful establishment of threatened species outside its native range) and 111 non‐CIP events (unsuccessful establishment of threatened species outside its native range after introduction), involving 174 terrestrial vertebrates. We then tested the relative importance of various predictors at the location, event, and species levels with generalized linear mixed models and model averaging. Successful CIP events occurred across taxonomic groups and biogeographic realms, especially for the mammal group in the Palearctic and Australia. Locations of successful CIP events had fewer native threat factors, especially less climate warming in invaded regions. The probability of a successful CIP event was highest when species introduction efforts were great and there were more local congeners and fewer natural enemies. These results can inform threatened species ex situ conservation and non‐native invasive species mitigation. [ABSTRACT FROM AUTHOR]

The New Zealand bottlebrush, Metrosideros excelsa (Myrtaceae), was introduced into South Africa in the 1940s as an ornamental plant and subsequently naturalized in coastal parts of the Cape Floristic Region. Knowledge of M. excelsa's propagule pressure and response to fire in South Africa can inform evaluation of the species' invasion potential and management. We assessed M. excelsa's canopy and soil seed banks in burnt and unburnt stands; and post‐fire regeneration via reseeding and resprouting in relation to fire severity and tree size. Soil seed banks were assessed using an emergence technique, but no seedlings emerged from soil collected under burnt or unburnt plants suggesting that the species does not maintain a viable soil‐stored seed bank or germination triggers were not met (though unlikely). The annual seed crop in the canopies of unburnt trees was approximately 0.5–23 million seeds per tree. Viability, assessed through tetrazolium stain testing, of canopy‐borne seeds on unburnt trees was 18%, whereas a canopy fire, ranging in severity from low to extreme, killed all canopy‐borne seeds. Fifteen months post‐fire, the seedling to pre‐fire (live) tree ratio was 0.01, whereas 43% of burnt trees survived via basal resprouting. Fire severity had a non‐linear effect on tree survival (survival was highest after medium and high fire severity and lowest after low and extreme fire severity), while larger trees were more likely to survive fire. These results suggest that even low‐severity (safe) burning may be a useful control measure as it kills canopy‐borne seeds and causes substantial mortality, particularly of smaller trees. An opportunistic evaluation of an uncontrolled (no comparison with untreated individuals) foliar herbicide application to post‐fire resprouting individuals also showed considerable (91%) mortality. However, rigorous herbicide trials (also with herbicide in conjunction with burning) are required to inform the management of M. excelsa. [ABSTRACT FROM AUTHOR]

Marine coastal habitats are often characterized by strong gradients of anthropogenic disturbance such as pollution, typically most severe at urban waterfronts. These variations create stress for local organisms leading to their distribution along the disturbance as a function of their tolerance. non-indigenous species (NIS) are considered more tolerant to anthropogenic disturbances than their native counterparts, thriving in urban areas, where native species are sparser. It is however not yet entirely clear if these distribution patterns are due to larval behavior and preferential settlement or post-settlement processes. In the present study, we investigated the abundance of adults and settlers of two native (Ostrea edulis, Mytilus galloprovincialis) and two non-indigenous (Magallana gigas, Xenostrobus securis) bivalves along a strong marine urban environmental gradient. Oysters had sparse abundances of both adults and settlers at all sites, with no obvious distributional gradients. The two mussel species showed different settler-adult distributions along the gradient. Both settlers and adults of the native mussel M. galloprovincialis strongly decreased moving from the outermost periurban site to the innermost urban site, consistent with preferential settlement of larvae according to environmental conditions. The non-indigenous adult mussel X. securis showed a distribution pattern opposite to that of M. galloprovincialis, markedly increasing in abundance from the outermost to the innermost site. This was not paralleled by the distribution of X. securis settlers, which established over a larger area, including sites where adults were essentially absent. The mismatch between settler and adult distributions for X. securis suggests that post-settlement factors dictate spatial adult distribution.

This study shows how YouTube™, a popular video website, is a powerful tool to document and improve our ability to manage freshwater pet release in Brazil. Based on a series of 24 videos chosen randomly using 19 standardized keywords posted by pet-keeping YouTubers between January 1, 2020 and March 20, 2023 (650 h of searching time), we documented the intentional release of 12 translocated and five non-native species involving 11 fish species, two freshwater stingray species, two freshwater turtle species, one freshwater crab species, and one crayfish species in multiple watersheds/ecoregions of Brazil. This is the first record of intentional introduction for 17 species in Brazilian inland waters. The main drivers behind pet release were excessive growth, "agreeableness" (i.e., compassion, pet owner's reluctance to euthanize the animal), and aggressive behavior. The videos documented the release of multiple freshwater pets in numerous freshwater ecosystems. Pet releases were predominantly into rural freshwater ecosystems rather than urban, with an introduction hotspot identified in the Southeast region. This finding is important because pet release is more common in urban than rural areas. While colonization pressure (i.e., number of translocated/non-native species that each pet owner released) was high, overall propagule pressure (i.e., number of individuals of a translocated/non-native species released into a region) was low with a total of 49 individuals released over the monitored period. Proactive management is key in reducing the incidence of pet release in Brazil, attainable through transforming pet shop owners into disseminators of correct information about species traits. Environmental authorities should create "Non-native Pet Amnesty Day" to provide the opportunity for people to surrender their non-native aquatic pets; YouTubers can engage in awareness actions on YouTube™ such as show the negative effects that aquatic pets can cause if introduced into the wild; Brazilian scientists turn into "science YouTubers" and provide arguments that can be used to disseminate reliable scientific messages about freshwater pet release. [ABSTRACT FROM AUTHOR]

Germination traits are components of invasion potential, and comparing seed traits in sympatric native and invasive species can offer insights into the invasion process. We characterized seed germination traits and how they influenced the success of Eragrostis mexicana, a native species, and Eragrostis tenuifolia, an exotic species (Poaceae) in Mexico, in the context of their potential for biological invasion. Seeds from both species were collected from four sites in a natural protected area in Mexico City, and the germination of seeds of different ages was conducted in experiments at different temperatures. E. tenuifolia exhibited higher germination percentages than the native E. mexicana across all treatments. Seed age had differential effects, with older seeds of the native E. mexicana germinating better, while E. tenuifolia performed better with younger seeds. Temperature positively impacted germination for both species, although E. mexicana was limited at lower temperatures. Exotic E. tenuifolia can germinate over a wider temperature range with earlier germination rates, and generate a seed bank lasting several years, which may contribute to naturalization. The importance of germination traits in the context of invasive species establishment underscores the potential role of seed banks in facilitating biological invasions. [ABSTRACT FROM AUTHOR]

Non-indigenous species (NIS) contribute to the decrease of native species' diversity on a local and global scale. One of Europe's most significant donors of freshwater invasions is the Ponto-Caspian Region. Following the construction of artificial canals connecting isolated waterbodies and the resulting heavy boat traffic, the Ponto-Caspian Amphipoda started to spread in Europe. Four amphipod species: Dikerogammarus haemobaphes, Dikerogammarus villosus, Pontogammarus robustoides and Chaetogammarus ischnus have invaded the Masurian Lakeland (North-eastern Poland). Based on literature and our data, we studied their distribution in 22 lakes in the region during the years 2001-2016. We analysed their distribution against several water quality parameters and levels of anthropogenic pressure. Our results also present the first records of two new invaders, D. villosus and C. ischnus, in the studied area. We show that the relative abundance and frequency of these two species rapidly increase and, simultaneously, the populations of the earlier invaders, i.e. D. haemobaphes and P. robustoides, decrease. The native species - Gammarus lacustris - seems to be negatively affected by NIS richness, as well as by the proximity of towns. The spread of NIS in the lakes appears to be facilitated by boating and the lower complexity of the shoreline. Our study shows how anthropogenic pressure, especially tourism, can facilitate bioinvasion, jeopardising native biodiversity unless appropriate regulations are implemented. [ABSTRACT FROM AUTHOR]

The geographical exchange of non-native species can be highly asymmetrical, with some world regions donating or receiving more species than others. Several hypotheses have been proposed to explain such asymmetries, including differences in propagule pressure, source species (invader) pools, environmental features in recipient regions, or biological traits of invaders. We quantified spatiotemporal patterns in the exchange of non-native insects between Europe, North America, and Australasia, and then tested possible explanations for these patterns based on regional trade (import values) and model estimates of invader pool sizes. Europe was the dominant donor of non-native insect species between the three regions, with most of this asymmetry arising prior to 1950. This could not be explained by differences in import values (1827-2014), nor were there substantial differences in the sizes of modelled invader pools. Based on additional evidence from literature, we propose that patterns of historical plant introductions may explain these asymmetries, but this possibility requires further study. [ABSTRACT FROM AUTHOR]

Copyright of Ecological Applications is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the patterns of plant invasions across vegetation types and identifying the underlying drivers for such patterns is essential to prioritize sites for the effective management of invasive species. We sampled three forest types (Shorea robusta, Dalbergia sissoo, and Tropical deciduous riverine forest) and two grasslands in south-central Nepal to evaluate the richness of naturalized and invasive alien plant species (IAPS). Species richness of naturalized species and the IAPS among vegetation types within each physiographic region was compared using analysis of variance and t-test, and the ordination was used to analyze species-environment relations. Of the total 327 species of vascular plants recorded, 14 % were naturalized, and over a third of the naturalized species were invasive. Grasslands had the highest richness of naturalized species and the IAPS. In contrast, S. robusta forest had the lowest naturalized and IAPS richness. Naturalized species richness increased with native species richness. Ordination revealed that a high number of IAPS were associated with areas exposed to frequent fire and livestock grazing and close to human settlements. The results suggest that the grasslands closer to the human settlements and exposed to frequent disturbance are vulnerable to the establishment of IAPS. Early detection and control of IAPS in such frequently disturbed grasslands would prevent their spread into the surrounding landscapes.

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The positive relationship between number of introduced individuals and introduction success has been widely proposed in invasion biology on theoretical and empirical grounds. Still, successful establishment has been reported for smaller-than-expected founding populations, thus we suspected that the role of chance in species introductions had been understated. To evaluate this proposition, we modeled the likelihood of success of a known small-introduction event, that of island canaries (Serinus canaria) to Midway Atoll. We built an individual-based, stochastic simulation model, populated with vital rates from wild canaries and related species, and projected population growth for 30 years under a variety of conditions. We used perturbation analysis and logistic regression to evaluate model sensitivities. Our optimistic baseline model returned a probability of establishment of roughly 50%, although the true probability would have been lower if any realized vital rates were below their optimistic values. Both sensitivity analyses were dominated by juvenile mortality, suggesting that a small change in this value has an outsized impact on the likelihood of introduction success. As such, we propose three factors that may have increased the likelihood of success for this introduction: behavioral plasticity in mate selection allowing opportunistic polygamy, resistance to inbreeding depression that is common in species with a history of captive breeding, and a reduction in juvenile mortality rates via human assistance. Our models suggest that chance can play a role in establishment likelihood for small founding populations even under optimistic conditions, but that case-specific factors are likely important in most successful small introductions. [ABSTRACT FROM AUTHOR]

Disturbance is a primary driver of exotic plant invasions, but why disturbance commonly favours exotics over natives is unresolved.To address this question, we conducted the first biogeographic study of disturbance across multiple plant species. We experimentally disturbed grasslands and added seeds of 34 plant species to plots in their native range and in two introduced ranges that differed in invasibility (susceptibility to invasion) to evaluate recruitment while examining potential influences of resource availability, native community recovery from disturbance (resilience) and life‐history traits in local species pools.Species pools in the native (donor) range were more strongly skewed towards ruderal taxa than species pools in the introduced ranges. This bias in the donor pool was exacerbated by introduction filters that further selected for ruderal traits, strongly skewing exotic species pools in the introduced ranges towards ruderals. Sown species, which reflected these trait patterns, benefited from disturbance universally, but their disturbance response was 10‐fold greater in the more invasible introduced range. This result was not explained by nutrient availability, which responded similar to disturbance across ranges. Nor was it driven by background propagule pressure, which was minimal. Rather, the exaggerated disturbance effect in the more invasible introduced range appeared to be driven by weak recovery of the native plant community that allowed ruderal‐biased exotics to proliferate.Overall, disturbance appeared to favoured exotics because they were much more likely than natives to be ruderal. However, this trait bias only corresponded with an invader advantage in the more invasible range where weak community resilience was linked to slow‐growing, stress‐tolerant natives that failed to rapidly recover space and resources. In contrast, in the less invasible introduced range, highly competitive native perennials quickly filled the disturbance gap, demonstrating high community resilience that appeared to limit invader recruitment.Synthesis: Biogeographic influences on local species pools can facilitate invader success following disturbance, but final invasion outcomes are conditioned by native community resilience. [ABSTRACT FROM AUTHOR]

The encroachment of invasive shrubs in forest understories can have detrimental effects on native plant recruitment. As a result, removal of invasive species is a common practice although long‐lasting success is rare. In order to effectively conserve and manage invaded forests, it is crucial to understand the mechanisms that drive shrub invasion, that is, high propagule pressure, low native resistance and exploitation of empty niches.To gain a deeper understanding of the invasion process in forest ecosystems we conducted a meta‐analysis of the work done in this topic. We collected data on invasive species and native community performance, and on the abiotic conditions of forest understories under low and high levels of shrub invasion. We analysed data from 124 articles that yielded 377 unique observations.Our results revealed that while invader performance did not vary by the mechanism of invasion, the impact on the native community was significantly detrimental when invasion occurred via low biotic resistance, and only marginally significant via propagule pressure. Invasive species performance was associated with increases in light availability, but not with other resources (soil water or nutrients). When assessing impact on native performance as a function of invasive performance, results were again only significant under the low biotic resistance mechanism. Lastly, impacts were stronger when invasion took place by a single invader.Synthesis and applications. Taken together, these results suggest that restoration efforts should focus on (i) increasing the presence of strong native competitors or functionally diverse native communities, (ii) decreasing sources of invasive shrub propagules while keeping the canopies closed when invasion occurs via high propagule pressure, (iii) avoiding management techniques that degrade or diminish canopy cover and (iv) prioritizing management of forest understories dominated by particularly impactful invasive shrubs. [ABSTRACT FROM AUTHOR]

Aim: In 2024, cargo vessels must meet the International Maritime Organization's global ballast water discharge standards (IMO D‐2) that limit the concentration of living organisms. D‐2 focuses on reducing invasion risk by reducing 'community propagule pressure (CPP)', though it does not consider colonization pressure (CP). Location: Global. Methods: We modelled risk differences in IMO D‐2‐compliant discharges (10 ind. m−3) for communities that had inverse patterns of CP and species' individual propagule pressures (IPP). Secondly, we determined the effect on risk of varying CPP and CP. As part of this, we tested whether the IMO D‐2 standard for zooplankton‐sized organisms of <10 individuals m−3 was an optimal choice. Risk was defined as probability of at least one species invading using four risk–release models. Results: Risk differed strongly at the D‐2 limit based on community composition. At low CPP (<25 ind. m−3), risk was strongly affected by CP for hyperbolic and linear risk–release models and weakly for exponential and logistic models, while CPP affected only the former two model types. Across a much wider range of CPP values, risk was affected by CP, CPP and by their interaction for all models. Main Conclusion: The IMO D‐2 standard for zooplankton‐sized organisms requires very low CPP and even lower IPPs in mixed‐species releases, which will impede successful colonization. Species‐abundance theory predicts that discharges meeting the D‐2 standard (low CPP) will also have low CP. Much more empirical data are required to determine whether vessels can consistently reduce CP as it lowers CPP in order to meet these requirements. [ABSTRACT FROM AUTHOR]

Ambrosia artemisiifolia is a highly invasive weed. Identifying the characteristics and the factors influencing its establishment and population growth may help to identify high invasion risk areas and facilitate monitoring and prevention efforts. Six typical habitats: river banks, forests, road margins, farmlands, grasslands, and wastelands, were selected from the main distribution areas of A. artemisiifolia in the Yili Valley, China. Six propagule quantities of A. artemisiifolia at 1, 5, 10, 20, 50, and 100 seeds m-2 were seeded by aggregation, and dispersion in an area without A. artemisiifolia. Using establishment probability models and Allee effect models, we determined the minimum number of seeds and plants required for the establishment and population growth of A. artemisiifolia, respectively. We also assessed the moisture threshold requirements for establishment and survival, and the influence of native species. The influence of propagule pressure on the establishment of A. artemisiifolia was significant. The minimum number of seeds required varied across habitats, with the lowest being 60 seeds m-2 for road margins and the highest being 398 seeds for forests. The minimum number of plants required for population growth in each habitat was 5 and the largest number was 43 in pasture. The aggregation distribution of A. artemisiifolia resulted in a higher establishment and survival rate. The minimum soil volumetric water content required for establishment was significantly higher than that required for survival. The presence of native dominant species significantly reduced the establishment and survival rate of A. artemisiifolia. A. artemisiifolia has significant habitat selectivity and is more likely to establish successfully in a habitat with aggregated seeding with sufficient water and few native species. Establishment requires many seeds but is less affected by the Allee effect after successful establishment, and only a few plants are needed to ensure reproductive success and population growth in the following year. Monitoring should be increased in high invasion risk habitats. [ABSTRACT FROM AUTHOR]

The expansion of alien plant species is of global concern, yet our understanding of their dispersal mechanisms is limited. Here we address the potential of alien plant seeds to disperse via ingestion, transport and egestion in waterfowl (endozoochory). Based on their general rapid expansions, we expected alien plant species to have several advantages for endozoochory compared to native plant species. We hypothesised that seeds of alien species would have higher passage rate, longer gut retention times, higher germinability after gut passage and shorter time‐to‐germination after egestion by waterfowl.In order to test our hypotheses, we compared the endozoochorous dispersal ability of six pairs of congeneric alien and native wetland plant species in a feeding experiment with mallards (Anas platyrhynchos). We focused on differences in seed survival, gut retention time, germinability and time‐to‐germination. In the analyses we corrected for seed shape and volume as these seed traits are known to have important effects.With gut passage, alien species had higher passage rates and germinated slower, whereas native species had shorter retention times and greater germinability. Controlling for seed traits did not alter these conclusions, but seed traits affected all aspects of the endozoochory process. This suggests that alien species may have particular traits correlated with a higher endozoochory potential. Among control seeds, alien seeds germinated faster and their germinability was higher than natives. Seed traits explained differences in germinability and time‐to‐germination in control seeds.Seeds of alien plant species have traits that correlate with successful endozoochory. This may provide alien species with a competitive advantage over native plant species by ensuring higher endozoochory rates in new environments, potentially enabling their rapid expansions. Our study underlines the important role of seed traits in the endozoochory potential of alien and native plant species, notably through their influence on retention time and germination. [ABSTRACT FROM AUTHOR]

The information on the number of mammalian species introduced and established into the Neotropical Region and the knowledge on their history of introduction and ecological-genetic aspects are rather variable. To improve our understanding on these topics, we provide an updated list of mammalian species that have established wild populations in the Neotropics and, where possible, compare genetic variability between native and introduced populations in order to evaluate whether the genetic paradox of invasions (GPI) applies to these species. Our search exposed an evident lack of genetic data for most populations introduced in the Neotropics, which restricted our analysis to 10 out of the 51 mammalian species introduced and to only three neutral molecular markers. Losses of genetic variability were a frequent feature of introduced populations, suggesting that these populations have overcome low genetic variation and successfully established in the new environment adding support to the conditions needed to be considered paradoxical in the sense of the GPI. However, it was not possible to affirm that the magnitude of the loss is related to the number of introduction events or the number of individuals introduced or translocated. Alternative approaches to obtain better estimates of genetic diversity associated with the evolutionary potential of the species at the initial stages of invasion are needed. They will provide valuable insight into ecological and evolutionary processes involved in biological invasions, and useful information for species-based risk assessment of invasion. [ABSTRACT FROM AUTHOR]

Simple Summary: North American bean thrips, Caliothrips fasciatus, native to California (U.S.), is a regular contaminant of navel oranges exported from California. Despite more than 100 years of accidental shipments overseas, this polyphagous thrips has not established outside of its native range. Understanding why this thrips has not successfully invaded other parts of the world may be explained, in part, by the effects of temperature on fitness. This study investigated the effects of nine fluctuating temperatures that averaged 8, 10, 15, 20, 25, 30, 32, 35, and 37 °C over a 24 h period on the developmental and reproductive biology of C. fasciatus to better understand the effects of temperature on these critical life history characters and how temperature may influence the invasion potential of this thrips. North American bean thrips, Caliothrips fasciatus, native to California U.S., has been detected inside the navels of navel oranges exported from California for more than 120 years. Despite this long history of accidental movement into new areas, this thrips has failed to establish populations outside of its native range. The cold accumulation hypothesis postulates that increasing levels of cold stress experienced by thrips overwintering inside navels is compounded when harvested fruit is shipped under cold storage conditions. Consequently, the fitness of surviving thrips is compromised, which greatly diminishes invasion potential. At the time this study was conducted, the effects of temperature on C. fasciatus fitness were unknown. To address this shortcoming, the effects of nine fluctuating temperatures that averaged 8, 10, 15, 20, 25, 30, 32, 35, and 37 °C over a 24 h period on the developmental and reproductive biology of C. fasciatus were evaluated. One linear and five nonlinear regression functions were fit to egg-to-adult development rate data for parent and offspring thrips to characterize thermal performance curves. Estimates of minimum, optimal, and maximum temperature thresholds for development were in the ranges of −4.37–6.52 °C (i.e., Tmin), 31.19–32.52 °C (i.e., Topt), and 35.07–37.98 °C (i.e., Tmax), respectively. Degree day accumulation to complete development, estimated from linear regression, ranged 370.37–384.61. Average development times for eggs, first and second instar larvae, propupae, pupae, and adult longevity, and mean lifetime fecundity of females were significantly affected by temperature. These biological responses to temperature may provide insight into how this abiotic variable affects the invasion potential of C. fasciatus. [ABSTRACT FROM AUTHOR]

Abstract Background The successful establishment of a species population following a single introduction of a few individuals to a non-native area has been limited. Nevertheless, the oriental fire-bellied toad (Bombina orientalis) population in Beijing is purportedly descended from a single introduction of about 200 individuals translocated from Yantai, Shandong Province, China, in 1927. Results To resolve the introduction process and to understand the genetic consequences since that introduction approximately 90 years ago, we investigated the population’s genetic diversity and structure using 261 toads from Beijing and two native Shandong populations and inferred the species’ introduction history using simulation-based approaches. Analysis of mitochondrial DNA (mtDNA) sequences showed the two haplotypes found in Beijing nested within Yantai haplotypes, thus corroborating the historical record of the translocation source. The mtDNA and 11 nuclear microsatellite markers revealed both considerably lower genetic diversity in Beijing than in the source population and strong genetic differentiation between them. Although the current census population in Beijing may be in the range of a few thousand, the effective population size was estimated at only 20–57. Simulations also suggest that this population may have descended from 40–60 founders. Conclusions The Beijing population’s genetic patterns were consistent with the consequences of a severe bottleneck during introduction followed by genetic drift. The introduction trajectory constructed for this B. orientalis population reveals the genetic footprints of a small population sustained in isolation for nearly a century. Our results provide an intriguing example of establishment success from limited founders and may inform ex situ conservation efforts as well as the management of biological invasions.

Most invasions start with the introduction of a few individuals and the majority fail to establish and become invasive populations. A possible explanation for this is that some species are subject to Allee effects—disadvantages of low densities—and fail to perform vital activities due to the low availability of conspecifics. We propose that 'facilitation' from native individuals to non-natives through heterospecific sociability could enhance chances of the latter establishing in novel environments by helping them avoid Allee effects and even reducing the minimum number of non-native individuals necessary to achieve the density for a viable population (the Allee effect threshold). There is evidence from experiments carried out with freshwater fish, snails, lizards, mussels and bird that supports the idea of heterospecific sociability between native and non-native species as a process to promote invasion success. We propose that to understand invasion success in social non-native species we need to investigate how they integrate into the recipient community. Furthermore, to manage them, it may be necessary to reduce population density not just below the Allee effect threshold but also to understand how natives could help them shift the conspecific Allee effect threshold to their benefit. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'. [ABSTRACT FROM AUTHOR]

Many of today's damaging invasive plants were intentionally introduced for pasture development and amenity. By examining the introduction history and consequent spread of these species, we can identify factors associated with their successful establishment and dominance. Using collated presence/absence and cover data, alongside a review of the literature and discussions with land managers, we present a comprehensive analysis of the introduction history and spread of the environmental and agricultural grassy weed, Bothriochloa pertusa (L.) A.Camus (Indian couch) throughout Queensland, Australia. Using this data, we also perform habitat suitability models to predict its potential distribution and local-scale cover across Queensland in relation to key environmental variables. We found that B. pertusa was introduced on multiple occasions and across a large area of Queensland, despite re-occurring doubts and poor evidence for its benefit to livestock production. Livestock grazing, associated disturbances (i.e. land clearing, soil erosion) and climatic extremes were commonly associated with its spread throughout the landscape. In 2020 the main area of B. pertusa invasion as indicated by occurrence records spanned 28,537,600 ha. Results from the habitat suitability models suggest the occurrence and local-scale cover of B. pertusa is largely determined by climate variables and the foliage projective cover of trees. Based on these results B. pertusa still has considerable capacity to spread and increase in dominance across many areas of Queensland, particularly further west and south of its current range. The introduction and spread history of B. pertusa suggests propagule pressure, traits, climate, land management and cultural perceptions are all key factors implicated in the spread of B. pertusa. Where B. pertusa has become dominant there has been a major shift in lifeform from native perennial tussock species to a grazing tolerant stoloniferous species. To slow this process of 'lawnification' we recommend more conservative grazing strategies and strategically selected protected areas to maintain cover of grazing sensitive native tussock grass species. [ABSTRACT FROM AUTHOR]

Interbasin water transfer projects (IBWT's) have emerged as dispersal corridors for aquatic species. However, little is known about how water transfer affects regional spread dynamics, or shapes the genetic diversity patterns of non-native populations. Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many wellestablished populations in IBWT's. Here, we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China. Our objectives were to (1) reveal the genetic diversity patterns of the Shimofuri Goby during regional spread, and (2) identify its mode of spreading in water transfer systems. We observed (1) a high level of genetic diversity in non-native populations without evidence of bottleneck effects, (2) that non-native populations with a longer water transfer times had a higher private allele richness, and (3) that non-native populations showed a highly mixed genetic structure, low level of genetic differentiation, and no significant relationship between geographical and genetic distances. Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae, and are probably related to propagule pressure caused by the construction of water transfer. To manage the non-native populations of T. bifasciatus, preventive actions and physical removal should be implemented in IBWT's. [ABSTRACT FROM AUTHOR]

Germination traits are components of invasion potential, and comparing seed traits in sympatric native and invasive species can offer insights into the invasion process. We characterized seed germination traits and how they influenced the success of Eragrostis mexicana, a native species, and Eragrostis tenuifolia, an exotic species (Poaceae) in Mexico, in the context of their potential for biological invasion. Seeds from both species were collected from four sites in a natural protected area in Mexico City, and the germination of seeds of different ages was conducted in experiments at different temperatures. E. tenuifolia exhibited higher germination percentages than the native E. mexicana across all treatments. Seed age had differential effects, with older seeds of the native E. mexicana germinating better, while E. tenuifolia performed better with younger seeds. Temperature positively impacted germination for both species, although E. mexicana was limited at lower temperatures. Exotic E. tenuifolia can germinate over a wider temperature range with earlier germination rates, and generate a seed bank lasting several years, which may contribute to naturalization. The importance of germination traits in the context of invasive species establishment underscores the potential role of seed banks in facilitating biological invasions.

High-latitude marine ecosystems have experienced fewer species invasions than temperate marine ecosystems, a discrepancy that may be attributed to barriers such as low propagule pressure, extreme and seasonal abiotic conditions, and biotic resistance of relatively intact communities. Each of these barriers is being affected by climate change and increasing human activity in high-latitude (>55º N) areas. We reviewed the evidence for each of these barriers limiting species invasion in high-latitude areas in the northern hemisphere. Based on records from government documents of high‐latitude countries, non-native species appear to be increasing in number (in Denmark and the United States) although there remains a paucity of data on invasive species establishment for high-latitude regions. Future study is needed to identify the drivers and impacts of invasions at high latitudes so that managers looking to prevent invasions can focus their efforts on bolstering barriers to invasion in these unique ecosystems.

Acacia longifolia (Sydney golden wattle) is considered one of the most problematic plant invaders in Mediterranean-type ecosystems. In this study, we investigate the species’ invasion history by comparing the genetic diversity and structure of native (Australia) and several invasive range (Brazil, Portugal, South Africa, Spain, and Uruguay) populations and by modelling different introduction scenarios using these data. We sampled 272 A. longifolia individuals – 126 from different invasive ranges and 146 from the native range – from 41 populations. We genotyped all individuals at four chloroplast and 12 nuclear microsatellite markers. From these data we calculated diversity metrics, identified chloroplast haplotypes, and estimated population genetic structure based on Bayesian assignment tests. We used Approximate Bayesian Computation (ABC) models to infer the likely introduction history into each invaded country. In Australia, population genetic structure of A. longifolia appears to be strongly shaped by the Bass Strait and we identified two genetic clusters largely corresponding to mainland Australian and Tasmanian populations. We found invasive populations to represent a mixture of these clusters. Similar levels of genetic diversity were present in native and invasive ranges, indicating that invasive populations did not go through a genetic bottleneck. Bayesian assignment tests and chloroplast haplotype frequencies further suggested a secondary introduction event between South Africa and Portugal. However, ABC analyses could not confidently identify the native source(s) of invasive populations in these two countries, probably due to the known high propagule pressure that accompanied these introductions. ABC analyses identified Tasmania as the likely source of invasive populations in Brazil and Uruguay. A definitive native source for Spanish populations could also not be identified. This study shows that tracing the introduction history of A. longifolia is difficult, most likely because of the complexity associated with the extensive movement of the species around the world. Our findings should be considered when planning management and control efforts, such as biological control, in some invaded regions. [ABSTRACT FROM AUTHOR]

Ballast water is recognized as a leading pathway for the introduction of aquatic non‐indigenous species which have caused substantial ecological damage globally.Following international regulations, most international ships will install a ballast water management system (BWMS) by 2024 to limit the concentration of aquatic organisms in ballast water discharges; however, these new technologies may not operate as expected at global ports having variable water quality or may periodically malfunction.Using simulations informed by empirical data, we investigated the risk of non‐indigenous species establishment associated with BWMS inoperability and evaluated potential mitigation strategies. Scenarios considered included bypassed or inoperable BWMS achieving no reduction in organisms, and partially functioning BWMS with discharged organism concentrations exceeding permissible limits. These scenarios were contrasted to outcomes with fully functioning BWMS and to voyages where ballast water exchange (BWE) was used to mitigate risk.Partially functioning BWMSs were nonetheless beneficial, reducing organism concentrations in ballast and thus establishment risk. When a BWMS is bypassed or partially functioning, BWE is a useful emergency mitigation measure, reducing establishment risks more than partial BMWS. However, the greatest risk reduction was achieved when partial BWMS and BWE were combined.Voyage‐specific characteristics such as concentration of organisms at uptake and destination port salinity can affect the optimal management strategy for voyages when the BWMS does not achieve compliant discharges.Synthesis and applications. The risk of aquatic invasions and their associated ecological damages can be substantially reduced by using a ballast water management system (BWMS) and/or ballast water exchange (BWE). When a BWMS is inoperable, appropriate mitigation measures should be decided on a trip‐by‐trip basis considering voyage route and reason for BWMS inoperability (when known). BWE is a useful strategy for reducing invasion risk, except when uptake concentrations are very low. Combining BWE and partial BWMS always reduced risk compared with BWE alone, but did not greatly reduce risk when uptake concentrations were high. [ABSTRACT FROM AUTHOR]

Sri Lanka, one of the world's biological hotspots, exports wild-caught and farm-bred aquarium fish species to more than 70 countries. This study evaluated the potential for invasiveness of aquarium fish species now raised and traded in Sri Lanka's Gampaha, Kandy, and Polonnaruwa districts. A questionnaire survey of 40 hobbyists, 20 retailers and ten breeders of aquarium fish in each selected district was conducted to assess the causes of aquarium fish releases. The invasion potential was evaluated using a model consisting of species thermal tolerance, propagule pressure and invasion history. Overall, 59 non-native fish species belonging to 14 families (Acanthuridae, Callichthyidae, Characidae, Cichlidae, Cyprinidae, Helostomatidae, Loricariidae, Notopteridae, Pimelodidae, Poeciliidae, Osphronemidae, Osteoglossidae, Salmonidae, and Scombridae) were recorded from the aquarium trade in the country. Out of 17 species with high to moderate invasive potential, six have already been established in the environment in Sri Lanka. Therefore, Astronotus ocellatus, Barbonymus schwanenfeldii, Carassius auratus, Hypostomus plecostomus, Pangasianodon hypophthalmus, Poecilia latipinna, P. sphenops, Puntigrus tetrazona, Trichopodus microlepis, Xiphophorus helleri, and X. maculatus are identified as potential invaders in Sri Lanka. The reasons for the intentional release of aquarium fish into the environment were excessively large size, aggressiveness, diseases and high reproductive rates. The number of fish of each species released into the natural environment is positively correlated to the number kept in home aquaria. A well-coordinated institutional mechanism to control unwanted fish introductions through the aquarium fish trade in Sri Lanka is urgently needed. [ABSTRACT FROM AUTHOR]

Ship ballast residual sediments are an important vector of introduction for non-indigenous species. We evaluated the proportion of residual sediments and associated organisms released during de-ballasting operations of a commercial bulk carrier and estimated a total residual sediment accumulation of ∼13 t, with accumulations of up to 20 cm in some tank areas that had accumulated over 11 years. We observed interior hull-fouling (anemones, hydrozoans, and bryozoans) and high abundances of viable invertebrate resting stages and dinoflagellate cysts in sediments. Although we determined that <1 % of residual sediments and associated resting stages were resuspended and released into the environment during individual de-ballasting events, this represents a substantial inoculum of 21 × 107 viable dinoflagellate cysts and 7.5 × 105 invertebrate resting stages with many taxa being nonindigenous, cryptogenic, or toxic/harmful species. The methods used and results will help estimate propagule pressure associated with this pathway and will be relevant for residual sediments and nonindigenous species management. • Detailed residual sediment accumulation was mapped in ship ballast tanks. • High residual sediment accumulation (up to 20 cm and 11-year-old) was found. • Residual sediments and associated fauna (<1 %) are released during de-ballasting operations. • High quantity of viable dinoflagellate cysts and invertebrate resting stages are released. • Better propagule pressure estimates are relevant for ship ballast sediment and NIS management. [ABSTRACT FROM AUTHOR]

Sowing native seeds is a common approach to reintroduce native plants to degraded systems. However, this method is often overlooked in wetland restoration despite the immense global loss of diverse native wetland vegetation. Developing guiding principles for seed‐based wetland restoration is critical to maximize native plant recovery, particularly in previously invaded wetlands. Doing so requires a comprehensive understanding of how restoration manipulations, and their interactions, influence wetland plant community assembly. With a focus on the invader Phragmites australis, we established a series of mesocosm experiments to assess how native sowing density, invader propagule pressure, abiotic filters (water and nutrients), and native sowing timing (i.e., priority effects) interact to influence plant community cover and biomass in wetland habitats. Increasing the density of native seeds yielded higher native cover and biomass, but P. australis suppression with increasing sowing densities was minimal. Rather, community outcomes were largely driven by invader propagule pressure: P. australis densities of ≤500 seeds/m2 maintained high native cover and biomass. Low‐water conditions increased the susceptibility of P. australis to dominance by native competitors. Early sowing of native seeds showed a large and significant benefit to native cover and biomass, regardless of native sowing density, suggesting that priority effects can be an effective restoration manipulation to enhance native plant establishment. Given the urgent wetland restoration need combined with the limited studies on seed‐based wetland restoration, these findings provide guidance on restoration manipulations that are grounded in ecological theory to improve seed‐based wetland restoration outcomes. [ABSTRACT FROM AUTHOR]

Question: What constrains Juniperus virginiana encroachment in semi‐arid grasslands: precipitation‐based constraints on establishment or dispersal‐based constraints on spread? Location: Sandhills grassland, Nebraska, USA. Methods: We tracked juvenile and adult stages of J. virginiana encroachment using field sampling and remote sensing across a network of 40 sites spanning a wide precipitation gradient (399–655 mm). Regional patterns of encroachment were then used to assess the relative support for precipitation‐based constraints on establishment versus dispersal‐based constraints on spread in a region transitioning to a more encroached state. Results: Woody encroachment was widespread and we found no evidence that low precipitation precludes encroachment in the Sandhills. Instead, encroachment patterns were best described by proximity to planted propagule sources. However, levels of encroachment were highly variable. Encroachment density was low at more arid sites that lacked nearby stands of planted J. virginiana, and encroachment tended to increase with proximity to plantings and higher mean annual precipitation, suggesting that both variables play a role in the rate of encroachment. Conclusion: Our results indicate that woody encroachment is constrained by dispersal in the Sandhills and that planted propagule sources increase grassland vulnerability to encroachment, regardless of mean annual precipitation. This may be true for other intact grassland regions where barriers to woody plant establishment have been altered or overcome. A key implication is that programs and policies need to consider encroachment risks from planted propagule sources and how to manage them to avoid fragmentation of intact grasslands. [ABSTRACT FROM AUTHOR]