Invasion Success Research Articles

Factors influencing variation in reproduction in invasive species: a case study of the Asian shore crab Hemigrapsus sanguineus

Reproductive success is a strong determinant of invasive species success. It is common for studies on invasive species to assess reproduction by measuring size-specific fecundity and scaling this up using population size or densities. Yet, reproductive success is influenced by numerous factors that are not accounted for in such calculations. We examined the influence of several factors on fecundity (clutch size) and egg size in the Asian shore crab Hemigrapsus sanguineus, including body size, spatial variation throughout the invaded range, season, fertilization success, brood loss, and diet. We show that all of these factors influence reproduction simultaneously within the invaded North American range of this species, though the relative importance of these different factors varied across sites or sampling times. Our study demonstrates that numerous factors may influence the reproductive success of invasive species and that studies that rely on fecundity measured at a single place and time, or that ignore factors such as offspring quality or brood loss, may provide a skewed picture of reproduction, and thus of potential invasive success.

A native herbaceous community exerts a strong allelopathic effect on the woody range-expander Betula fruticosa

Abstract Biological invasions by alien and range-expanding native plant species can suppress native plants through allelopathy. However, the homeland security hypothesis suggests that some native plants can resist invasion by producing allelopathic compounds that inhibit the growth of invasive plants. Most research has focused on allelopathic interactions between individual native and invasive plant species, with less emphasis on how allelopathy helps entire native communities resist invasions. Additionally, limited knowledge exists about allelopathic interactions between range-expanding native species and recipient native communities, and their influence on invasion success. To bridge this knowledge gap, we conducted two greenhouse competition experiments to test reciprocal allelopathic effects between a native woody range-expanding species, Betula fruticosa, and a community of four native herbaceous species (Sanguisorba officinalis, Gentiana manshurica, Sium suave and Deyeuxia angustifolia) in China. We assessed whether B. fruticosa and the native community differed in their competitive effects and responses, and whether these were influenced by activated carbon, which neutralizes allelochemicals in the soil. Activated carbon reduced the suppressive effects of the native community on the above-ground biomass of B. fruticosa, which indicates that the native community exerted a strong allelopathic effect on B. fruticosa. In contrast, activated carbon only marginally enhanced the suppressive effects of B. fruticosa on the native community, which indicates that allelopathy is not the primary mechanism by which B. fruticosa exerts its suppression. Overall, these findings support the homeland security hypothesis and suggest that biotic resistance from the native herbaceous community may limit the invasion success of the woody range-expander B. fruticosa.

Different behavioral profiles between invasive and native nudibranchs: means for invasion success?

Behavior is predicted to be a primary determinant of the success of the invasion process during the early phases of colonization. Comparing invaders with sympatric native species may provide a good approach to unravel behavioral traits involved in an invasion process. In this study, we carried out an experimental simulation of the introduction and the acclimatization phase into a new environment and assessed the expression of activity, alertness, and habituation in an invasive Mediterranean population of the South African nudibranch Godiva quadricolor comparing its profiles with those of the sympatric Mediterranean native nudibranchs Cratena peregrina and Caloria quatrefagesi. Individuals of these 3 species were subjected to 3 behavioral tests: spontaneous activity, carried out in the introduction phase (immediately after sampling) and after a week of acclimatization; alert test, in which a potential threat was simulated by means of a tactile stimulus, and habituation test, in which the same alert test stimulus was repeated 5 times at 30-min intervals. The invasive G. quadricolor showed higher levels of exploration activity, thigmotaxis, alertness, and sensitization than the native species. These behavioral traits may represent pivotal drivers of the ongoing invasion process.

Self‐help or self‐sabotage? A common invader's soil legacy does not impede, and may facilitate, potential competitors

AbstractIntroduced plants create lasting abiotic and biotic changes to soil that are increasingly implicated as major drivers of invasion success, yet models for investigating patterns in the impacts of these soil legacies are lacking. Here, we used Bohemian knotweed (Reynoutria × bohemica) to present a novel approach for testing whether accounting for diverse evolutionary drivers can clarify how an invader's soil legacy mediates its success. For most tested species, R. × bohemica's soil legacy did not influence seedling performance irrespective of its evolutionary history or the evolutionary novelty of species that share its soil. However, we found the relative importance of legacy effects versus other mechanisms of invader dominance depends on the life stage of the plants growing in soil conditioned by the invader. While the effects of R. × bohemica's soil legacy on seedling performance were context dependent, emergence was, on average, higher in R. × bohemica‐conditioned soils than in unconditioned soils. Thus, contrary to theory, R. × bohemica's soil legacy not only fails to impede potential competitors but may also facilitate them. Our results are particularly powerful: we detected novel insights in the face of biological complexity, even for R. × bohemica, which likely does not depend on heterospecific plant–soil feedbacks for its competitive dominance in its introduced range. Designing rigorous investigations that explore how plant species' evolutionary histories mediate an invader's soil legacy across diverse abiotic environments, as shown here, is key for producing insights in other systems.

Multiple introductions of divergent lineages and admixture conferred the high invasiveness in a widespread weed (Hypochaeris radicata).

Biological invasion consists of spatially and temporally varying stages, accompanied by ecological and evolutionary changes. Understanding the genomics underlying invasion dynamics provides critical insights into the geographic sources and genetic diversity, contributing to successful invasions across space and time. Here, we used genomic data and model-based approaches to characterize the invasion dynamics of Hypochaeris radicata L., a noxious weed in Korea. Genetic diversity and assignment patterns were investigated using 3563 SNPs of 283 individuals sampled from 22 populations. We employed a coalescent-based simulation method to estimate demographic changes for each population and inferred colonization history using both phylogenetic and population genetic model-based approaches. Our data suggest that H. radicata has been repeatedly been introduced to Korea from multiple genetic sources within the last 50 years, experiencing weak population bottlenecks followed by subsequent population expansions. These findings highlight the potential for further range expansion, particularly in the presence of human-mediated dispersal. Our study represents the first population-level genomic research documenting the invasion dynamics of the successful worldwide invader, H. radicata, outside of Europe.

Nutrient enrichment, propagule pressure, and herbivory interactively influence the competitive ability of an invasive alien macrophyte Myriophyllum aquaticum.

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. 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 native macrophyte 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. 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. 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 nutrient-rich 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.

Functional Segregation of Resource Utilization Strategies between Invasive and Native Plants and Invasion Mechanisms in the Water Level Fluctuation Zone: A Case Study of Pengxi River in Three Gorges Reservoir, China

The ecosystem of the water level fluctuation (WLF) zone of the Three Gorges Reservoir (TGR) is highly vulnerable and sensitive due to its unique cyclical flooding and drought conditions. The ecological impact of biological invasion in this area is particularly severe, making it crucial to study the differences in resource utilization strategies between invasive plants (IPs) and native plants (NPs) using functional traits to explore the mechanisms of invasion. We selected the WLF zone of Pengxi River in the TGR area and conducted a multi-scale study along the elevation gradient. The results reveal that at the regional scale, IPs have a larger height and specific leaf area, smaller leaf tissue density, and specific root length compared to NPs, showing a preference for enhancing aboveground resource acquisition over leaf defense capabilities. They allocate more tissue construction resources to their roots to withstand environmental pressures, which may be the key to their successful intrusion, highlighting the role of niche differentiation. On the community scale, the H and SLA of IPs and NPs are positively correlated with elevation, while the LTD of IPs shows a negative correlation. At elevations of 175 m and below, IP and NP exhibit functional convergence, while above 175 m, functional divergence was observed. This indicates that although the different resource utilization strategies are crucial for successful IP invasion, the environmental filtering from periodic floods and drought pressures play a significant role in community assembly in the WLF zone, allowing IP to integrate into habitats with similar functional characteristics already inhabited by NP and establish their own communities.

Age and Density of Mated Females Affect Dispersal Strategies in Spider Mite Tetranychus ludeni Zacher.

The dispersal strategies of a species can affect its invasion success. Investigations into the dispersal strategies of invasive species in relation to different factors help improve our understanding of invasion mechanisms and provide knowledge for population management and invasion evaluation. Tetranychus ludeni Zacher (Acari: Tetranychidae) is an invasive species which is native to Europe but is now cosmopolitan. Here, we examined the effects of age and density on dispersal in mated females. Our results show that older females that are capable of producing more eggs within 24 h were more likely to disperse and moved longer distances than younger ones with fewer eggs. Older females spread most of their eggs out of their natal habitats and over longer distances, which reduced competition and increased offspring fitness. Females exhibited significantly increased dispersal probability and distances with an increase in population density to avoid crowding. The synchronization of dispersal and reproduction, along with the positive density-dependent dispersal strategy, may facilitate the habitat colonization and invasion speed of T. ludeni.

Warming induced shade tolerance to become a key trait in invasion success of free-floating plant Pistia stratiotes over the native Hydrocharis morsus-ranae

Changes in nutrient concentration, temperature and light intensity due to climate change can alter the species composition of aquatic ecosystems, since global climate change can intensify the process of eutrophication. Eutrophication can enhance the biological invasion and the distribution of alien aquatic plants. Here we investigated the competition ability of alien Pistia stratiotes and native Hydrocharis morsus-ranae and the effect of different light intensities, temperatures and nutrient concentrations on the functional traits of the two species. In short term (8 days) monoculture experiment, we applied low (0.5 mg L-1 N; 0.05 mg L-1 P) and high nutrient concentrations (2 mg L-1 N; 0.2 mg L-1 P), four different light intensities (25–295 μmol m−2 s−1) as well as cold and warm (21.5; 27.5 ± 0.5°C) water treatments in full factorial design. In mixed cultures we cultivated the plants for 28 days with various biomass ratio, in shaded and well illuminated conditions, at a high nutrient concentration (4 mg L-1 N 1 mg L-1 P). In monocultures, the relative growth rate of P. stratiotes in warm water was significantly higher than that of H. morsus-ranae, however, this difference was not significant in colder water. In the co-culture experiment, P. stratiotes had significantly higher growth rate compared to H. morsus-ranae regardless of initial plant biomass ratio. Under shaded (65 ± 5 μmol m−2 s−1) conditions, P. stratiotes outcompeted H. morsus-ranae, resulting in its decay. Experimental results imply that with elevated temperature, the spread of alien P. stratiotes can be expected. Furthermore, under shaded conditions, P. stratiotes has a higher chance of occupying the water surface over the native plant H. morsus-ranae.

River hydrology mediates fish invasions in Addo Elephant National Park, South Africa

Invasive freshwater fish can often have severe negative effects on native fishes in river systems. The interactions between hydrology and habitat variability can mediate the speed and success of individual invasions and the consequent impact on biodiversity. The rivers within Addo Elephant National Park (AENP) in the Eastern Cape, South Africa experience cyclical droughts and wet periods and as a result are naturally episodic. These rivers were recently invaded by three non-native species, the invasive largemouth bass (Micropterus salmoides) as well as the extralimital sharptooth catfish (Clarias gariepinus) and Mozambique tilapia (Oreochromis mossambicus). Monitoring of key sampling sites along two rivers over a 12-year period that included two major droughts revealed unexpected patterns in the spread of these species and their interactions with native fishes. On the Coerney River, C. gariepinus repeatedly invaded and was extirpated from a seasonal reach of the river, wherein O. mossambicus was only occasionally captured. On the Wit River, two apparently independent introductions of M. salmoides in the lower and upper reaches of the river resulted in patchy habitat occupancy over the course of 12 years. While C. gariepinus regularly co-occurred with native species, M. salmoides appeared to locally extirpate the endangered Eastern Cape redfin (Pseudobarbus afer). During drought, both species persisted in close but disconnected pools, suggesting that the episodic hydrology and geomorphology of these rivers may offer temporary predation refugia for native species during drought.Conservation implications: Drought in episodic rivers can mitigate against the impact and spread of freshwater invasions within protected areas. Effects of drying on invasion corridors and spatial interactions with native species should be taken into consideration when managing such invasions. Severe droughts also offer an opportunity to actively control invasive species when they are confined to accessible drought refugia within the protected area.

Impact of temperature and season on ant foraging activity of two invasive species in a Mediterranean urban area

Abstract Invasive species often have harmful effects on human activities and biodiversity. The Tapinoma nigerrimum complex includes three species that exhibit invasive traits and the ability to form supercolonies, including Tapinoma magnum and Tapinoma darioi. While these species are native to the Mediterranean basin, they have recently been reported as invasive in more northern regions of Europe. However, T. magnum and T. darioi show different invasion patterns in Europe, suggesting differences in thermal preferences between these species. We aimed to determine whether there was any difference in activity pattern depending on temperature or season between the two Tapinoma species and between Tapinoma and co‐occurring native Mediterranean ants. We measured ambient temperature and ant foraging activity around the nest entrances of T. darioi and T. magnum in urbanised sites around Montpellier, southern France, over almost 1 year. We did not detect differences in activity between the two species according to temperature, but T. magnum was more active than T. darioi in winter. Compared to the co‐occurring native species, the two Tapinoma species were more active at low temperatures and earlier in the year. These results suggest that the difference in invasion success between T. magnum and T. darioi may not be explained by temperature preference. The difference in activity between native Mediterranean species and invasive Tapinoma suggests a coexistence through niche partitioning. In addition, our results suggest that control measures against invasive Tapinoma species would be more effective if applied at the end of winter.

Introduced species shed friends as well as enemies

Many studies seeking to understand the success of biological invasions focus on species’ escape from negative interactions, such as damage from herbivores, pathogens, or predators in their introduced range (enemy release). However, much less work has been done to assess the possibility that introduced species might shed mutualists such as pollinators, seed dispersers, and mycorrhizae when they are transported to a new range. We ran a cross-continental field study and found that plants were being visited by 2.6 times more potential pollinators with 1.8 times greater richness in their native range than in their introduced range. Understanding both the positive and negative consequences of introduction to a new range can help us predict, monitor, and manage future invasion events.

Effect of the host plant on the life history, behaviour and fungal community of a fungus‐farming ambrosia beetle

Abstract Although there are benefits to being a generalist, the majority of herbivorous insects are diet specialists. This raises the question whether the ability to reproduce on various host plants hides an unknown ecological optimum. Our study investigated the existence of such an ecological optimum in the fungus‐farming ambrosia beetle, Xyleborinus saxesenii Ratzeburg (Coleoptera: Curculionidae). We hypothesised that X. saxesenii may exhibit higher fitness in specific hosts that are particularly abundant in their respective regions. To test this hypothesis, we bred X. saxesenii from a broadleaved forest population in semi‐artificial media mimicking either a coniferous or a broadleaved host‐tree species. As trade‐offs between different traits can occur, we examined various aspects of the life history, social behaviour and fungal symbionts of X. saxesenii. We found that dispersing females did not exhibit any preference, and that the host tree did not have any impact on life history parameters or larval and adult behaviours. The fungal community associated with the species was made up of identical fungal species, albeit with different relative abundances between host trees. Our findings indicate that X. saxesenii does not exhibit a specific adaptation to the most abundant host trees in its native habitat. However, we identified significant effects of laboratory breeding on life history traits, social behaviour and adult dispersal. This generalism in host use in combination with inbreeding mating system may be the main drivers of the invasion success of the Eurasian X. saxesenii, which is currently among the most prevalent and widely distributed ambrosia beetle species worldwide.

Successful invasion: camera trap distance sampling reveals higher density for invasive raccoon dog compared to native mesopredators

Monitoring population parameters of invasive species gains importance as these species continue to expand all over the world. Monitoring of invasive mammalian mesopredators is, however, complicated due to their nocturnal and secretive behaviour. In the European Union, the most common invasive mesopredator is the raccoon dog (Nyctereutes procyonoides), which causes concerns for native species, such as endangered waterfowl that may be subject to nest predation. We studied the density of mesopredators in southern Finland with wildlife cameras, using methodology of distance sampling. We deployed in total of 175 camera traps around 11 (spring 2020) and 16 (spring 2021) lakes or wetlands. We inferred densities for raccoon dogs, and for native mesopredators the red fox (Vulpes vulpes) and the European badger (Meles meles) for comparison. Raccoon dogs were found to have higher overall as well as site-specific densities (about 3.7 ind./km2) than badgers (1.2 ind./km2) and red foxes (0.6 ind./km2). The raccoon dogs also were present at every study wetland, while badgers were not found at all sites. The red fox showed more diurnal activity compared to raccoon dogs and badgers. Camera trap distance sampling enabled us to provide a density estimates on a rather small spatial and temporal scale for species of similar size and movement speed. It could therefore prove valuable as a long-term monitoring option, as climate trends are likely to further enable raccoon dog expansion. Currently this invasive species appears to be the most common mesopredator around wetlands in the southern boreal zone of southern Finland.

Alien emergent aquatic plants develop better ciprofloxacin tolerance and metabolic capacity than one native submerged species

Antibiotic pollution and biological invasion pose significant risks to freshwater biodiversity and ecosystem health. However, few studies have compared the ecological adaptability and ciprofloxacin (CIPR) degradation potential between alien and native macrophytes. We examined growth, physiological response, and CIPR accumulation, translocation and metabolic abilities of two alien plants (Eichhornia crassipes and Myriophyllum aquaticum) and one native submerged species (Vallisneria natans) exposed to CIPR at 0, 1 and 10 mg/L. We found that E. crassipes and M. aquaticum's growth were unaffected by CIPR while V. natans was significantly hindered under the 10 mg/L treatment. CIPR significantly decreased the maximal quantum yield of PSII, actual quantum yield of PSII and relative electron transfer rate in E. crassipes and V. natans but didn't impact these photosynthetic characteristics in M. aquaticum. All the plants can accumulate, translocate and metabolize CIPR. M. aquaticum and E. crassipes in the 10 mg/L treatment group showed greater CIPR accumulation potential than V. natans indicated by higher CIPR contents in their roots. The oxidative cleavage of the piperazine ring acts as a key pathway for these aquatic plants to metabolize CIPR and the metabolites mainly distributed in plant roots. M. aquaticum and E. crassipes showed a higher production of CIPR metabolites compared to V. natans, with M. aquaticum exhibiting the strongest CIPR metabolic ability, as indicated by the most extensive structural breakdown of CIPR and the largest number of potential metabolic pathways. Taken together, alien species outperformed the native species in ecological adaptability, CIPR accumulation and metabolic capacity. These findings may shed light on the successful invasion mechanisms of alien aquatic species under antibiotic pressure and highlight the potential ecological impacts of alien species, particularly M. aquaticum. Additionally, the interaction of antibiotic contamination and invasion might further challenge the native submerged macrophytes and pose greater risks to freshwater ecosystems.

Heterospecific sociability and foraging behaviour of an invasive livebearer fish

AbstractHeterospecific sociability could enhance invasion success in social species since social non‐natives usually belong to small founding populations during the early stages of invasion. The twospot livebearer (Pseudoxiphophorus bimaculatus) is native to Central America and southern Mexico and is recently recognised as invasive in the Mexican Central Plateau, where it poses a threat to native species. Here, we evaluated twospot livebearer sociability towards either a conspecific pair or a shoal of four fish with one of four possible compositions, all conspecifics or two conspecifics combined with either two guppies, two porthole livebearers or two twoline skiffias. In a second experiment, foraging time, latency to feed, first fish to begin foraging and aggressive interactions were recorded under the same social conditions used in the sociability experiment, with body size included as a covariate in both experiments. All focal twospot livebearers spent significantly more time with the given shoals rather than with the available space in the aquarium. They showed a higher tendency to associate with small shoals of conspecifics than with pairs. Larger twospot livebearers associated more, regardless of the social condition. Twospot livebearer fed more with porthole livebearers, less with guppies and similarly with twoline skiffias. Latency to forage did not vary significantly between social conditions. Twospot livebearers were involved in more aggressive interactions when with guppies or porthole livebearers than when with native twoline skiffias or conspecifics. Twospot livebearers could gain benefits from associating with natives and conspecifics, but not with other invasive poeciliids. Heterospecific shoaling behaviour with natives may enhance invasion success during early stages when conspecifics are scarce while associating with other invasive poeciliids could lead to increased competition. Further research is needed on heterospecific interactions of non‐natives to better understand their behavioural role in invasion likelihood.

Acidic Apple Snails: Effects of Climate Change on the Mechanical Properties of an Invasive Gastropod.

Climate change can directly and indirectly affect species distribution. Warming may allow for invasive species, such as apple snails, to migrate to higher latitudes where temperatures are more conducive to their survival and invasion success. Higher temperatures and lower pH ranges have been previously documented to affect the form and function of calcium carbonate shells, which serve many functions, including protection from predators and thermoregulation. This study aimed to quantify differences in the morphology and mechanical properties of invasive apple snail, Pomacea maculata, shells after altering temperature and pH. We mechanically tested shells among three five-week treatments: control, higher temperature, and lower pH. Ultimate Strength increased in shells that were exposed to higher temperatures, but Young's Modulus and Peak Load did not differ among control, temperature, and pH treatments. Apple snails in higher temperature tanks increased their shell length over the five-week trials. Although snail morphometrics did not differ between sexes, male shells exhibited a higher Peak Load, Young's Modulus, and Ultimate Strength compared to female shells. Our findings are consistent with previous gastropod studies, in that a lower pH is associated with a decrease in shell size, and higher temperatures yield larger snail shells with a higher ultimate strength. Peak Load did not significantly differ among treatments, which suggests that the cross-sectional area is relatively important when considering this species mechanical performance today and in future climates. Due to the intense nutritional and calcium demands of egg production, female snails may be more susceptible to weakened shells due to low pH environments caused by climate change.

Unveiling allelopathic dynamics and impacts of invasive Erigeron bonariensis and Bidens pilosa on plant communities and soil parameters

Invasive alien species are becoming more and more prevalent worldwide, Erigeron bonariensis and Bidens pilosa are two invasive species of Asteraceae in Egypt. To mitigate their detrimental effects and understand their differences in invasiveness, we compared the allelopathic potentials of E. bonariensis and B. pilosa using leachates, decaying residues, and volatilization processes. Notably, the allelopathic variances in leachates were significant, influenced by plant types, concentrations, and response patterns of target plant traits, as indicated by EC50. The relative phytotoxicity of the invasive species decayed residues peaked between 20 and 25 days in the soil, with a positive correlation with concentrations and soil properties. The highest quantities of phenolic acids were chlorogenic acid and caffeic acid reaching (5.41 and 4.39 µg g−1) E. bonariensis and (4.53 and 4.46 µg g−1) B. pilosa, in leachates extracts respectively, while in the soil extract of decayed residues were coumaric acid and ferulic acid measuring (1.66 and 1.67 µg g−1) E. bonariensis and (1.47 and 1.57 µg g−1) B. pilosa, respectively. Using GC/MS analysis, the main volatile components in E. bonariensis were 1, 8 cineole (5.62%), and α-terpinene (5.43%) and iso-Caryophyllene (5.2%) which showed the greatest inhibitory effects. While B. pilosa main constituents were trans-sabinene (5.39%) and Camphene (5.11%), respectively. Finally, the high invasion level displayed from E. bonariensis (0.221) compared with B. pilosa (0.094) which correlated with the stronger allelopathic activities against plant species, and soil properties. Therefore, the allelopathic potentialities of these species are critically relevant to their invasion success.

Exotic plant species with longer seed bank longevity and lower seed dry mass are more likely to be invasive in China

Abstract Globalization of social and economic activities has led to the large-scale redistribution of plant species. It is still unclear how the traits aid the successful invasion of alien species. Here, we downloaded global plant trait data from the TRY-Plant Trait Database and classified alien species in China into four groups: high, medium, need attention and harmless according to their distribution and degree of harm to local plant communities based on existed studies. The relationship between plant functional traits and invasion level was clarified, and we established a prediction model based on plant functional traits and taxonomy. The results showed that species with smaller seeds, smaller individuals, lower special leaf area and longer seed bank longevity (SL) are more likely to be an invasive species after introduction to foreign ecosystems. In summary, exotic species with longer SL and lower seed dry mass are more likely to be invasive in China. We also trained two predictive models to check if we can predict a species’ invasion. Combining the two models together, statistically, we could predict if a species is invasive from its traits and taxonomy with a 91.84% accuracy. This model could help local governments, managers and stakeholders to evaluate shall we introduce some plant species in China.

Biological invasions are a population-level rather than a species-level phenomenon.

Biological invasions pose a rapidly expanding threat to the persistence, functioning and service provisioning of ecosystems globally, and to socio-economic interests. The stages of successful invasions are driven by the same mechanism that underlies adaptive changes across species in general-via natural selection on intraspecific variation in traits that influence survival and reproductive performance (i.e., fitness). Surprisingly, however, the rapid progress in the field of invasion science has resulted in a predominance of species-level approaches (such as deny lists), often irrespective of natural selection theory, local adaptation and other population-level processes that govern successful invasions. To address these issues, we analyse non-native species dynamics at the population level by employing a database of European freshwater macroinvertebrate time series, to investigate spreading speed, abundance dynamics and impact assessments among populations. Our findings reveal substantial variability in spreading speed and abundance trends within and between macroinvertebrate species across biogeographic regions, indicating that levels of invasiveness and impact differ markedly. Discrepancies and inconsistencies among species-level risk screenings and real population-level data were also identified, highlighting the inherent challenges in accurately assessing population-level effects through species-level assessments. In recognition of the importance of population-level assessments, we urge a shift in invasive species management frameworks, which should account for the dynamics of different populations and their environmental context. Adopting an adaptive, region-specific and population-focused approach is imperative, considering the diverse ecological contexts and varying degrees of susceptibility. Such an approach could improve and refine risk assessments while promoting mechanistic understandings of risks and impacts, thereby enabling the development of more effective conservation and management strategies.