When native and non-native congeners use the same resource, non-natives can competitively exclude natives. To clarify the effects of native ants on competitive interactions between native and non-native congeners, we experimentally investigated interactions between a native wasp species, Anterhynchium flavomarginatum, and a recently invading congener, Anterhynchium gibbifrons (Hymenoptera: Vespidae), using control and ant-excluded trap nests in central Japan. A total of 48 trap nests (12 bamboo canes per trap nest) were placed at forest edges between June and October 2021. Ants, which are native predators and nest-site competitors of Anterhynchium wasps, were experimentally excluded from half of the trap nests using a sticky barrier. Out of 288 control and 288 ant-excluded bamboo canes, A. flavomarginatum nested in 5.6
The genus Ceratocystis includes several invasive pathogens that have caused severe disease in native and cultivated plants following introduction into new regions. Rapid ‘ōhi’a death (ROD), resulting from infection by C. lukuohia and C. huliohia, has caused widespread death of Metrosideros polymorpha (‘ōhi ‘a lehua) in Hawai’i since its detection in 2010. Should these pathogens be introduced into Aotearoa New Zealand or other South Pacific nations, they have the potential to infect Metrosideros spp. and other plants, including important crops. Presence of susceptible Metrosideros spp. across the Pacific, combined with extensive tourism and trade networks, could facilitate a stepwise spread of the pathogens. Movement of people and goods, including contaminated soil and plant materials, represents a primary dispersal pathway. Biological factors, including associations with ambrosia beetles, may further influence pathogen spread. Preliminary observations suggest several Metrosideros spp. endemic to Aotearoa New Zealand are susceptible, and asymptomatic infections could allow undetected pathogen movement. Climate modelling suggests that regions of Aotearoa New Zealand, particularly the North Island, provide suitable conditions for ROD establishment. Unknowns include host susceptibility, beetle vector ecology, and the diversity of Ceratocystis already in the region. Weather variation may intensify this risk by expanding the pathogens’ geographic and host ranges and altering interactions among hosts, pathogens and insects associated with their spread, including ambrosia beetles. This review emphasises the importance of ongoing research, surveillance, and preparedness, particularly with the absence of curative treatments, to mitigate the potential impacts of ROD in Aotearoa New Zealand and the wider South Pacific.
Species invasions remain a key contributing factor to the global rise in extinction rates of native fishes in freshwater ecosystems. While efforts to remove non-native species from newly invaded water bodies often target well-established ecological characteristics and habitat associations, invasive species may exhibit different behaviour to conspecifics in their native range. Brown bullhead catfish (Ameiurus nebulosus) is a widespread invader characterized in their native range as a thermophilic nocturnal littoral-benthic predator with high site fidelity. We used acoustic telemetry to examine seasonal movement patterns and habitat use of catfish in Lake Rotoiti, a recently invaded lake in Aotearoa-New Zealand. Invasive catfish demonstrated strong habitat niche plasticity and thermal niche rigidity. Only in spring and summer were catfish regularly found in nearshore areas (between shore and < 7 m bottom depth). Instead, catfish were highly mobile, especially in autumn when catfish routinely occupied offshore regions (≥ 7 m bottom depth; 80
Biological invasions are a dominant driver of global ecological change. It is known that invasive species can limit the survival or growth of native species, yet their full impact on biodiversity can be complex. We investigated the impact of the invasive tree Neltuma juliflora on avian communities in Brazil’s Caatinga, a seasonally dry tropical forest region. Comparing intact natural riverine forest to thickets invaded with N. juliflora, we found that N. juliflora thickets act as an ecological filter that reorganize avifauna. Contrary to expectations of simple diversity loss, invaded habitats exhibited significantly higher local (alpha) avian diversity. However, this increase was driven by a surge in generalist and open-habitat specialist species, while forest specialists declined significantly. Beta diversity analysis revealed this community shift was overwhelmingly due to species balanced variation (turnover) (92.6
Zebra mussels (Dreissena polymorpha) were discovered in the Great Lakes of North America in the mid-1980s, and the presence of quagga mussels (D. bugensis) occurred a few years later. Due to the extreme environmental effects of these invasive mussels and the near impossibility of removing them once colonies are established, predicting and subsequently impeding their spread is important. Both mussel species have been gradually invading North America, from the Great Lakes westward, primarily transported on trailered watercraft. The purpose of this study was to use annual watercraft traffic data to develop modified discrete-time Markov chain models of potential dreissenid mussel invasion of waterbodies in a non-infested state (Idaho). The results showed that, of all Idaho waterbodies, Lake Coeur d’Alene has the highest likelihood of dreissenid mussel infestation because it receives the highest volume of watercraft traffic. Lake Pend Oreille poses the greatest risk of spreading dreissenid mussel infestation because of high watercraft traffic volume going from this lake to adjacent waterbodies. A high to low risk ranking of Idaho waterbodies becoming infected, should a dreissenid mussel infestation occur, was also determined. The models developed could be useful to prevent a dreissenid mussel infestation by focusing countermeasures at high-risk waterbodies. These models can be used, in the event of a dreissenid mussel invasion, to prioritize the protection of vulnerable waterbodies geographically located near the infested waterbody location. Lastly, the models in this study are adaptable and could be configured to provide risk assessment for other invasive organisms vectored by trailered watercraft.
Waterlogging, exacerbated by climate change, acts as a major abiotic force that reshapes plant communities and promotes biological invasions in riparian and wetland ecosystems. Mikania micrantha, one of the world’s most invasive plants, displays high tolerance to hydric environments, yet the physiological and molecular mechanisms underlying this tolerance remain unresolved. Here, we integrated morphological, physiological, and transcriptome data to dissect the responses of M. micrantha under shallow (stem-base) and deep submergence. Under deep submergence, underwater leaves exhibited significantly increased specific leaf area (SLA) and decreased chlorophyll a/b ratio, while dark respiration rates were downregulated—which collectively enhanced light capture while minimizing respiratory carbon loss. Transcriptomic profiling of these leaves revealed downregulation of genes involved in carbon fixation in photosynthetic organisms, consistent with an energy-conservation strategy under light-limited and hypoxic conditions. In striking contrast, submerged adventitious roots (ARs) showed transcriptional reorganization, with upregulation of photosynthesis. Further experiments demonstrated that these roots developed functional chloroplasts, achieved net photosynthetic oxygen evolution, and showed enhanced bicarbonate (HCO3−) utilization capacity. Collectively, our results demonstrate that M. micrantha employs a suite of integrated organ-level functional adjustments—combining leaf metabolic reprogramming, photosynthetic adventitious roots, and coordinated hormonal regulation—to maintain carbon homeostasis under prolonged waterlogging. This study provides new insights into the mechanisms that facilitate M. micrantha’s success in wetland habitats, highlighting the species’ increasing ecological risk to native wetland biodiversity under future climate scenarios.
Invasive plants are often observed and assumed to be locally abundant, which likely increases their ecological impacts. However, there are few macroscale comparisons of invasive versus non-invasive species’ abundance, making it unclear if abundance is a consistent trait of invasive plants. We categorized 1,603,243 observations of 10,581 species across the contiguous United States and within EPA Level I ecoregions (areas of ecological similarity) as invasive, introduced (non-native and non-invasive), or native to the U.S. and further identified native species that are invasive elsewhere. We created empirical cumulative distribution functions to visually compare differences between groups and compared distributions using Kolmogorov–Smirnov pairwise tests. Nationally, invasive plants had significantly higher abundance distributions and percent cover (mean = 5.29
Rhizosheath formation, defined as the aggregation of soil particles adhering to root surfaces, is an important rhizosphere trait linking root morphology with soil aggregation and resource acquisition. However, its trait-based drivers across species with contrasting ecological strategies, particularly invasive and non-invasive taxa, remain poorly understood. In this study, eight selected Asteroideae species representing invasive and non-invasive groups were evaluated to quantify rhizosheath formation and its relationship with root morphological traits. Plants were grown under controlled conditions and sampled at 30 and 45 days after sowing. Rhizosheath mass, root biomass, root length, and root hair density were measured, and a rhizosheath competitiveness index was calculated by normalizing rhizosheath mass with root biomass. Rhizosheath mass increased significantly with plant age and varied among species. Strong positive relationships were observed between rhizosheath mass and root biomass, root length, and root hair density. A multiple regression model explained a large proportion of the variation in rhizosheath formation, indicating that root traits are key determinants of this process. Invasive species exhibited significantly higher rhizosheath competitiveness index values than non-invasive species, suggesting greater soil-binding efficiency per unit root biomass despite comparable absolute rhizosheath mass. Root biomass showed the strongest overall association with rhizosheath formation, whereas the direct contributions of root length and root hair density to rhizosheath formation efficiency appeared comparatively weaker. These findings indicate that rhizosheath formation is strongly associated with root morphological traits, with root biomass emerging as the primary predictor under the present experimental conditions, whereas root length and root hair density showed comparatively weaker contributions.
Alien species often establish successfully by exploiting opportunities created by human-induced disturbances. However, the effects of disturbance may differ among plant groups with contrasting life-history strategies and depend on disturbance timing relative to species establishment. This study examined how mowing and its timing influence the establishment and dominance of Erigeron annuus and whether mowing-induced changes in plant groups with contrasting life-history strategies alter vegetation succession. Field surveys were conducted at two sites in Korea to assess the effects of mowing on relative light intensity, E. annuus establishment, and importance values across life-history groups. Mowing opened the vegetation canopy and significantly increased light availability near the soil surface. The density and coverage of E. annuus increased under mowed conditions, whereas the absence of mowing did not promote its establishment. However, mowing conducted in late September did not increase either the density or coverage of E. annuus in the following year. Mowing also increased the importance value of E. annuus, while the summed importance values of perennial species decreased. These findings suggest that repeated mowing, when it creates gaps during the establishment period of E. annuus, facilitates its persistent invasion and delays succession by suppressing perennial species. Therefore, effective management of E. annuus in human-managed landscapes requires a successional perspective that focuses not simply on removing aboveground biomass, but on minimizing gap formation during the germination and establishment period and maintaining stable coverage of perennial herbaceous communities.
Biological invasions are a major contemporary driver of biodiversity loss and economic impacts, and their outcomes often depend on invader reproduction processes. Across environmental gradients, variation in abiotic and biotic conditions (including plant–soil interactions), can strongly influence seedling establishment, a key bottleneck for invaders’ spread. Mycorrhizal fungi may further modulate this process depending on environmental context and symbiont availability. In Andean Patagonia (Argentina), the conifer Juniperus communis has been identified as an incipient invader along a precipitation gradient spanning forest, shrubland, and steppe habitats. However, its mycorrhizal associations and their relationship with environmental conditions remain poorly understood. Here, we characterized the mycorrhizal status (presence, type, and abundance) of naturally established J. communis seedlings along a precipitation gradient in Patagonia, and evaluated its relationships with environmental factors and seedling growth. Seedling abundance was higher in wetter forest habitats than in shrubland and steppe sites. While ectomycorrhizal associations were absent, arbuscular mycorrhizal colonization was consistently high and similar among habitats (72.6
Biological invasions are increasing threats to biodiversity, ecosystem functioning, and conservation management in mountain ecosystems, yet comprehensive information on invasive and potentially invasive alien plants across the Mount Kilimanjaro elevational gradient remains limited. This study assessed the composition, diversity, distribution, community structure, and invasion risk of invasive and potentially invasive alien plants across low, mid, and high elevation zones of the Mount Kilimanjaro ecosystem, northern Tanzania. Vegetation data were collected from 150 stratified random grid cells using nested quadrats for shrubs and herbaceous species. Species were classified as invasive or potentially invasive alien plants using national invasive species guidelines, herbarium records, published literature, and global databases. Species richness, abundance, diversity indices, community composition, and invasion risk were analysed using non-parametric tests, PERMANOVA, species accumulation curves, Pareto analysis, and an adapted Australian Weed Risk Assessment protocol. A total of 21 invasive alien plant species and 35 potentially invasive alien plant species were recorded. Invasive alien plants were mainly represented by Fabaceae and Asteraceae, while potentially invasive alien plants were distributed across several families, particularly Asteraceae, Amaranthaceae, Poaceae, and Euphorbiaceae. Forbs dominated both invasive and potentially invasive alien plant groups. Species richness of invasive alien plants was highest at low and mid elevations and lowest at high elevations, whereas potentially invasive alien plants showed peak species richness and abundance at mid elevations. PERMANOVA revealed significant differences in species composition among elevation zones for both invasive and potentially invasive alien plants, indicating clear species turnover along the elevational gradient. Risk assessment identified a small subset of species contributing disproportionately to invasion pressure. High-risk invasive alien plant species included Lantana camara, Prosopis juliflora, Caesalpinia decapetala, Parthenium hysterophorus, and Argemone mexicana while Ageratum conyzoides, Cyperus rotundus, and Conyza bonariensis emerged as high-risk potentially invasive alien plant species. These findings provide baseline evidence to support early detection, risk-based prioritization, and adaptive management of invasive and potentially invasive alien plants in this globally significant mountain ecosystem.
Horticultural trade is the primary pathway for the introduction of invasive plant species. Increasingly, trade is conducted online via e-commerce platforms. We used automated web scraping to capture snapshots of the online plant trade in Australia across 11 e-commerce websites between 2020 and 2023, aiming to identify potentially invasive species for sale. We identified 3,822 species for sale, which we categorised based on their Australian regulatory, naturalisation and native status, as well as their evidence of impacts elsewhere. We found the sale of 194 ‘Priority’ species, which are already considered invasive in Australia; 544 ‘Attention’ species, which have naturalised in Australia; and 175 ‘Watch’ species that are invasive elsewhere in the world but have not yet naturalised in Australia. We further prioritised the 175 Watch species, highlighting four species (Berberis thunbergii, Artemisia vulgaris, Rosa rugosa, and Elaeagnus angustifolia) for immediate investigation based on global occupancy and abundance, climate suitability, propagule pressure, and evidence of impacts. We also evaluate invasion risk across e‑commerce platform types, finding that public online marketplaces list more plant taxa over time than nursery websites and that marketplaces and generalist nurseries tend to offer species with higher invasion risk than specialist nurseries. We recommend that this dataset is used as an aid for prioritising weed risk assessments by government authorities to prevent the establishment of new invasive plant species.
In the mid-1980s, sun-corals Tubastraea spp. were accidentally introduced to the Brazilian coast as oil and gas platform biofouling. Today, sun-corals are widespread along the Brazilian coastline, including several marine protected areas where dense populations are established. Recent observations in southeastern Brazil suggested that, in saturated localities, sun-coral adult colonies frequently detach from the rocky reef and accumulate on the unconsolidated substrate. Here, we conducted an in situ experiment of approximately 70 days to evaluate the effects of sun-coral deposition on macrofaunal assemblages across four cover levels (0, 33, 66, and 100
Biological invasions increasingly threaten ecosystems and agriculture. The spotted-wing drosophila, Drosophila suzukii, has been recognized as a highly polyphagous invasive pest. In South America, many of D. suzukii collecting sites overlap with native cactus species distribution and cacti are available resources throughout the year, including times when the crops are absent. However, D. suzukii capacity to develop on cactus hosts has not been experimentally evaluated. Here we evaluate the prickly pear cactus, O. sulphurea, as a potential alternative host by conducting no-choice oviposition assays and rearing larvae on a semi-natural cactus diet. We compared the viability, developmental time, morphological and reproductive traits, and fatty acid profiles of flies reared on cactus against two laboratory diets. Females laid eggs on cactus tissue, and larvae successfully completed development with fitness parameters and fatty acid profiles of adults comparable to the standard diets. These findings indicate that O. sulphurea could be a suitable breeding resource for D. suzukii, suggesting that it may serve as an alternative host during periods in which cultivated fruits become unavailable. These results may have implications for pest management programs and ecological dynamics.
The introduction of plant species beyond their native ranges has profound ecological and socio-economic consequences, particularly for grasses, which are frequently introduced and often highly successful invaders. This study analyses the diversity, distribution, and invasion dynamics of subspontaneous Poaceae across Western Europe. Using a comprehensive database compiled from specialised sources, 478 subspontaneous grass taxa were assessed, of which 46 were classified as invasive. Patterns in taxonomic richness, geographical origins, climatic affinities, residence time, and drivers of invasiveness were examined. Subspontaneous richness varied substantially among countries, with Belgium, the Netherlands, and France exhibiting the highest values, while invasive taxa generally represented a minor fraction (< 10
Ageratina adenophora poses significant threats to agricultural and forestry production and biodiversity conservation worldwide. However, its expansion mechanism in highly acidic environments has not been studied in depth. To address this issue, we investigated the impacts of A. adenophora invasion on soil nutrient content and enzyme activity levels across 24 samples from Yunnan Province, China. The sampling sites were categorized into four invasion levels, namely, initial invaded (C), lightly invaded (L), moderately invaded (M), and severely invaded (S). Our findings revealed that the soil pH in severely invaded areas was 8.37
Climate warming is driving widespread shifts in phenology, yet species often respond at different rates, potentially altering ecological interactions. Uneven advancement in flowering times among taxa can restructure patterns of co-flowering and influence resource availability for pollinators. Callery pear (Pyrus calleryana Decne.) is a prolific invasive in North America known for its abundance of early-blooming, aromatic, showy white flowers. We scored phenology for > 15,000 specimens of Callery pear and three common spring-blooming native or naturalized confamilials from 1850 to present to examine how climate shapes long-term phenological trends and co-blooming dynamics. Flowering times advanced across taxa, but since invasion in the late twentieth century, the invasive exhibited the most pronounced shift (> 22 days in 34 years), far outpacing natives and naturalized species (all < 13 days) since its introduction. These changes have reconfigured co-flowering associations, with the invasive now overlapping more strongly with early-blooming confamilials than with later-blooming taxa. Winter temperature was a key predictor of phenological advance, and earlier flowering of Callery pear was more strongly associated with warmer winters than the native and naturalized species. Callery pear showed a rapid phenological advance in its native range as well, indicating high phenological plasticity in the species may have existed prior to invasion. Our findings demonstrate high temperature-sensitivity in Callery pear has rapidly altered its temporal niche and patterns of co-blooming with non-invasive relatives in North America. Understanding these dynamics is critical for predicting ecological outcomes under ongoing global change.
In recent years, the Pacific brown macroalga Rugulopteryx okamurae has rapidly expanded across Mediterranean and Atlantic coasts, generating major ecological and socio‑economic impacts. In this study we examined the effects of exudates released by R. okamurae on the early developmental stages of two autochthonous sea urchin species, Paracentrotus lividus and Arbacia lixula, which are key benthic grazers in the invaded regions. Fertilized eggs were exposed for three days to different concentrations of R. okamurae exudates, and subsequent effects on survival, growth, and developmental abnormalities were determined for both sea urchin species. Acute exposure to 50 g L⁻1 exudates caused about 90
Microplastic pollution and biological invasions are converging in human-modified landscapes, yet their interactive effects remain poorly understood. Current research emphasizes chemical toxicity, but microplastics also function as particulate stressors that physically restructure soil environments. I propose the Triple-Filter Hypothesis, a framework reconceptualizing microplastics as contemporary biophysical filters that can reshape invasion trajectories through three mechanistic pathways. The Dispersal Filter posits that physical adhesion between propagules and plastic particles creates altered dispersal associations favoring species with adhesive seed surfaces. The Abiotic Filter proposes that soil structural modification imposes selection for flexible root architectures and stress-tolerant physiologies. The Biotic Filter hypothesizes that disruption of plant–soil–microbiome feedbacks differentially affects species depending on their mycorrhizal dependencies. Current evidence provides strongest support for abiotic mechanisms, while dispersal and biotic pathways remain largely untested. I identify three methodological limitations hindering progress: taxonomic parochialism, phylogenetic confounding, and ecologically unrealistic experimental concentrations. Advancing this field requires shifting from phenomenological description toward mechanistic hypothesis testing through biophysical validation, phylogenetically controlled designs, and multi-stressor experiments under field-realistic conditions. The Triple-Filter Hypothesis provides a testable structure for evaluating whether microplastics function as ecological filters in contemporary Anthropocene ecosystems.
