Biological Invasions Research Articles

Identification of alarm pheromone components of the southern giant Asian hornet, Vespa soror, a major pest of honey bees.

The rise of biological invasions threatens biodiversity and food security, with the vespid family, including Vespa soror, being of particular concern. Our study focused on the alarm pheromone components of V. soror. By using gas chromatography-mass spectrometry (GC-MS) chemical analyses, electroantennograms, and field bioassays, we identified 5 compounds-2-pentanol, 3-methyl-1-butanol, 2-heptanol, 2-nonanol (2-N), and isopentyl acetate (IPA)-in hornet sting venom that elicited defensive behavior from hornets. IPA and 2-N also serve as alarm pheromone components in multiple honey bee species that are important prey for V. soror. This shared chemical signaling may allow cross-detection by each species on the other's alarm cues. While it should be advantageous for bees to detect V. soror alarm pheromone, the benefits to V. soror of using IPA and 2-N are unclear. V. soror may manipulate bee behavior, potentially distracting defenders, because they mark victim bee colonies by rubbing their abdomens, which contain their sting glands, at bee hive entrances. Our findings pose new evolutionary questions about the role of manipulation in the arms races.

Trouble on the horizon: anticipating biological invasions through futures thinking

ABSTRACTAnticipating future biosecurity threats to prevent their occurrence is the most cost‐effective strategy to manage invasive alien species. Yet, biological invasions are complex, highly uncertain processes. High uncertainty drives decision‐making away from strategic preventative measures and towards operational outcomes aimed at post‐invasion management. The limited success of preventative measures in curbing biological invasions reflects this short‐term mindset and decision‐makers should instead apply strategic foresight to imagine futures where biosecurity threats are minimised. Here, four major futures thinking tools (environmental scanning, driver‐mapping, horizon scanning, and scenario planning) that describe probable, possible, plausible and preferable futures are assessed in terms of their potential to support both research and policy addressing biological invasions. Environmental scanning involves surveying existing data sources to detect signals of emerging alien species through knowledge of changes in either the likelihood or consequences of biological invasions. Several approaches are widely used for biosecurity including automated scans of digital media, consensus‐based expert scoring, and prediction markets. Automated systems can be poor at detecting weak signals because of the large volume of ‘noise’ they generate while expert scoring relies on prior knowledge and so fails to identify unknown unknowns which is also true of prediction markets that work well for quite specific known risks. Driver‐mapping uses expert consensus to identify the political, economic, societal, technological, legislative, and environmental forces shaping the future and is a critical component of strategic foresight that has rarely been applied to biological invasions. Considerable potential exists to extend this approach to develop system maps to identify where biosecurity interventions may be most effective and to explore driver complexes to determine megatrends shaping the future of biological invasions. Horizon scanning is a systematic outlook of potential threats and future developments to detect weak signals of emerging issues that exist at the margins of current thinking. Applications have been strongly focused on emerging issues related to research and technological challenges relevant to biosecurity and invasion science. However, most of these emerging issues are already well known in current‐day research. Because horizon scanning is based on expert consensus, it needs to embrace a diversity of cultural, gender, and disciplinary diversity more adequately to ensure participants think intuitively and outside of their own subject boundaries. Scenario planning constructs storylines that describe alternative ways the political, economic, social, technological, legislative, and environmental situation might develop in the future. Biological invasion scenario planning has favoured structured approaches such as standardised archetypes and uncertainty matrices, but scope exists to apply more intuitive thinking by using incasting, backcasting, or causal layered analysis. Futures thinking in biological invasions has not engaged with decision‐makers or other stakeholders adequately and thus outcomes have been light on policy and management priorities. To date, strategic foresight addressing biological invasions has applied each approach in isolation. Yet, an integrated approach to futures thinking that involves a diverse set of stakeholders in exploring the probable, possible, plausible, and preferable futures relating to biological invasions is crucial to the delivery of strategic biosecurity foresight at both national and global scales.

Coastal exotic plant serves as a habitat for a notorious wetland pest in unfavorable seasons: A case study of exotic Spartina alterniflora in China

Coastal biological invasions pose a wide-reaching threat to various ecosystems, affecting both vegetation and herbivores in native communities. Although herbivores often exert strong top-down control on vegetation, the impact of invasive species on consumers that strongly regulate native species in invaded ecosystems remains unclear. Therefore, through field surveys and feeding preference experiments, this study examined the effects of the invasive Spartina alterniflora Loisel. (hereafter, Spartina) on the native moth Laelia coenosa Hübner (hereafter, Laelia), a notorious pest that has been documented to cause significant damage to native Phragmites australis (Cav.) Trin. ex Steud. (hereafter, Phragmites) marshes in coastal wetlands of China. Field surveys showed that Laelia larvae were more abundant and had higher grazing rates in Phragmites than in Spartina marshes in summer, but these patterns reversed in autumn. Feeding experiments consistently showed that the dietary preference of Laelia larvae switched from Phragmites in summer to Spartina in autumn, likely because Spartina has a longer growing season and relatively higher nutritional quality than Phragmites in autumn. Thus, by providing shelters (i.e., dietary sources and habitats) during unfavorable seasons, Spartina invasions may facilitate this insect pest Laelia and potentially amplify its damage to native wetland vegetation. Our work reveals a novel, indirect mechanism of coastal invasion impacts and highlights the importance of incorporating seasonal variation in plant-herbivore interactions.

Invasion stage and competition intensity co-drive reproductive strategies of native and invasive saltmarsh plants: Evidence from field data

Biological invasion poses a significant threat to biodiversity conservation and also results in substantial economic loss including the excessive cost of management to control it. Still, its impact on plant sexual reproduction strategies remains underexplored in natural settings. We conducted a field experiment on native Phragmites australis and invasive Spartina alterniflora in Bohai Bay and assessed plant size (aboveground biomass and height) and sexual reproduction (ear biomass, reproductive allocation, etc.) in conjunction with water and soil properties. The results showed that during the early stage of invasion, the two species declined in size and sexual reproduction, with S. alterniflora showing a lesser decline than P. australis. However, in the late stage of invasion, S. alterniflora maintained its plant size by reducing its investment in sexual reproduction. Moreover, significant reproductive allometries were demonstrated by S. alterniflora under different competition intensities. P. australis displayed heightened sensitivity to water properties and soil non-resource conditions, while S. alterniflora adapted its inherent traits and environmental tolerance. S. alterniflora allocated more resources to thriving as an individual, while P. australis prioritized reproduction by increasing seed production. Overall, this study revealed the reproductive strategies that invasive and native species employ in response to competition and environmental factors, thereby offering crucial insights for conservation and management efforts.

Comparative landscape genomics reveals species-specific spatial patterns and suggests human-aided dispersal in a global hotspot for biological invasions

Comparative landscape genomics reveals species-specific spatial patterns and suggests human-aided dispersal in a global hotspot for biological invasions

Reconstructing the biological invasion of noxious invasive weed Parthenium hysterophorus and invasion risk assessment in China.

Invasive alien plants (IAPs) present a severe threat to native ecosystems and biodiversity. Comprehending the potential distribution patterns of these plant invaders and their responses to climate change is essential. Parthenium hysterophorus, native to the Americas, has become an aggressively invasive species since its introduction to China in the 1930s. This study aims to collect and reconstruct the historical occurrence and invasion of P. hysterophorus. Using the optimal MaxEnt model, the potential geographical distributions of P. hysterophorus were predicted based on screened species occurrences and environmental variables under the current and three future scenarios in the 2030s, 2050s, and 2070s (i.e., SSP1-2.6, SSP2-4.5, and SSP5-8.5), and the invasion risk of P. hysterophorus in Chinese cities, croplands, forests, and grasslands was assessed. The results show that: (1) The species initially invaded highly suitable areas and further spread to regions with non-analogous climate conditions. (2) Under the current climatic conditions, the overall potential distribution of P. hysterophorus is characterized by more in the southeast and less in the northwest. Climate variables, including mean annual temperature (bio1), precipitation in the wettest month (bio13), isothermality (bio3), and temperature seasonality (bio4), are the primary factors influencing its distribution. (3) The potential distribution of P. hysterophorus will expand further under future climate scenarios, particularly toward higher latitudes. (4) Forests and crop lands are the areas with the most serious potential invasion risk of P. hysterophorus. Therefore, we suggest that the government should strengthen the monitoring and management of P. hysterophorus to prevent its spread and protect agro-ecosystems and human habitats. Depending on the potential risk areas, measures such as quarantine, removal, and publicity should be taken to mitigate the threat of P. hysterophorus invasion and to raise awareness of P. hysterophorus invasion prevention.

Rodent competition and fire alter patterns of mound and disk formation of western harvester ants.

Consumers exert top-down controls on dryland ecosystem function, but recent increases in fire activity may alter consumer communities in post-fire environments. Native consumers, including ants and rodents, likely have critical roles in defining post-fire plant community assembly and resilience to biological invasions. This study aimed to understand how western harvester ants (Pogonomyrmex occidentalis) that form mounds and large vegetation-free disks that significantly influence plant community structure in the Great Basin Desert respond to fire and rodent community abundance. We tested this by installing treatment plots that excluded or allowed rodents and were burned or unburned in a full factorial design. We measured ant disk and mound size and density in each experimental plot. Fire increased ant mound density by 126% compared to unburned plots. Rodent presence decreased mound density by 59%, mound diameter by 13%, and mound height by 166%. We also show an interaction where the adverse effects of rodents on ant disk density were greater in burned than in unburned plots. The results suggest that booms in rodent populations are likely to have suppressive effects on ant mound and disk formation in native shrublands but that harvester ants may be released from rodent competition with the emergence of invasive grass-fire cycles.

Salivary detection of Chikungunya virus infection using a portable and sustainable biophotonic platform coupled with artificial intelligence algorithms

The current detection method for Chikungunya Virus (CHIKV) involves an invasive and costly molecular biology procedure as the gold standard diagnostic method. Consequently, the search for a non-invasive, more cost-effective, reagent-free, and sustainable method for the detection of CHIKV infection is imperative for public health. The portable Fourier-transform infrared coupled with Attenuated Total Reflection (ATR-FTIR) platform was applied to discriminate systemic diseases using saliva, however, the salivary diagnostic application in viral diseases is less explored. The study aimed to identify unique vibrational modes of salivary infrared profiles to detect CHIKV infection using chemometrics and artificial intelligence algorithms. Thus, we intradermally challenged interferon-gamma gene knockout C57/BL6 mice with CHIKV (20 µl, 1 X 105 PFU/ml, n = 6) or vehicle (20 µl, n = 7). Saliva and serum samples were collected on day 3 (due to the peak of viremia). CHIKV infection was confirmed by Real-time PCR in the serum of CHIKV-infected mice. The best pattern classification showed a sensitivity of 83%, specificity of 86%, and accuracy of 85% using support vector machine (SVM) algorithms. Our results suggest that the salivary ATR-FTIR platform can discriminate CHIKV infection with the potential to be applied as a non-invasive, sustainable, and cost-effective detection tool for this emerging disease.

Persistent biological invasions alter ecological network topology, impacting disease transmission during community assembly

Ecological networks experiencing persistent biological invasions may exhibit distinct topological properties, complicating the understanding of how network topology affects disease transmission during invasion-driven community assembly. We developed a trait-based network model to assess the impact of network topology on disease transmission, measured as community- and species-level disease prevalence. We found that trait-based feeding interactions between host species determine the frequency distribution of the niche of co-occurring species in steady-state communities, being either bimodal or multimodal. The width of the growth kernel influences the degree-biomass relationship of species, being either weakly positive or strongly negative. When this relationship is weakly positive, species-level disease prevalence is primarily correlated with biomass. However, when the degree-biomass relationship is strongly negative, species-level disease prevalence is determined by the difference between a host species’ in-degree and out-degree closeness centrality. At the community level, disease prevalence is generally amplified by increasing host richness, community biomass, and the standard deviation of interaction generality, while it is diluted by higher network connectance. Our framework verifies the amplification effects of host richness during invasion-driven community assembly and offers valuable insights for estimating disease prevalence based on host network topology.

Effects of alligator weed invasion on wetlands in protected areas: A case study of Lishui Jiulong National Wetland Park

Wetlands are one of the ecosystems most easily and severely invaded by alien species. Biological invasions can have significant impacts on local plant communities and ecosystem functioning. While numerous studies have assessed the impacts of biological invasions on wetlands, relatively few have been conducted in protected areas such as national wetland parks. We conducted a field survey to investigate the effects of the invasive herb Alternanthera philoxeroides (alligator weed) on the productivity and structure of plant communities and soil microbial communities in the Lishui Jiulong National Wetland Park in Zhejiang, China. We also examined the potential influence of the distance to the river edge on the impact of the alligator weed invasion. The alligator weed invasion significantly altered the plant community structure. It reduced the coverage of co-occurring plant species, including native (−31.2 %), invasive (−70.1 %), and non-invasive alien plants (−58.4 %). However, it increased species richness by 50 %, Pielou's evenness by 20 %, and Simpson's diversity index by 29.1 % for the overall plant community. Furthermore, within the community not invaded by alligator weed, increasing the distance to the river edge decreased the number of native plants by 57.0 % and the aboveground biomass of other invasive plants by 78.6 %. Contrary to expectations, no effects of the alligator weed invasion were observed on soil fungal and bacterial communities. Therefore, the impacts of the alligator weed invasion varied with spatial context and plant category, emphasizing the need to consider multiple scales and environmental factors when assessing the effects of invasive species on plant biodiversity. These insights enhance our understanding of plant invasions in wetlands and can guide the development of effective management strategies for these important ecosystems.

Tracking aquatic non-native macroinvertebrate species in Germany using long-term data

Biological invasions pose a global challenge, threatening both biodiversity and human well-being. Projections suggest that as invasions increase, the financial costs associated with management and the ecological harm they cause will also escalate. Here, we examined whether long-term biomonitoring strategies were adequate to identify and track benthic aquatic non-native macroinvertebrate species by using the German subset (151 time series; 129 of which reported non-native species) of the currently most comprehensive European long-term dataset of 1816 macroinvertebrate community time series from 22 European countries. The detection of aquatic non-native species was directly linked to the availability of long-term sites and thus, monitoring effort, having identified the spatio-temporal occurrence of 32 non-native species. The available long-term monitoring site data were mostly concentrated in the western part of Germany, predominantly covering the Rhine River and its tributaries. The spatially biased network of long-term monitoring sites, therefore, naturally skews the detection and reporting of aquatic non-native species toward this area and underestimates Eastern and Southern regions, impeding the comprehension of invasion dynamics. However, based on the available data, we found that the absolute number of non-native species increased and the proportion of non-native species relative to native species decreased over time. This indicates complex ecological interactions between native and non-native species and underlines the value of long-term data for investigating invasion dynamics. Considering the value of comprehensive monitoring networks, a spatially biased network delays the application of management and mitigation plans, possibly worsening the ecological and economic effects of biological invasions in Germany. The results provided here indicate the disadvantages of biased datasets, but simultaneously underline the enormous potential of a dense network of long-term monitoring. Our results also highlight the urgent need to increase and diversify long-term biomonitoring efforts throughout Germany to cover the main freshwater resources and their connections where the introduction risk of non-native species is the highest. Centrally collating such data would provide a profound basis for the monitoring of spreading aquatic non-native species and could serve the implementation of national biosecurity efforts.

Reciprocal transplant experiments demonstrate a dynamic coevolutionary relationship between parasitic mussel larvae and bitterling fishes

Abstract The coevolutionary dynamic of host–parasite associations varies from strictly local adaptations to diffuse guild coevolution. How innate and acquired immune responses modulate host resistance to parasitism and how host specificity and geographic scaling affect the efficacy of host response have consequences for range dynamics and biological invasions. Using reciprocal transplant experiments, we tested whether local or diffuse coevolution shapes host response to parasitism in the host–parasite association between bitterling fishes and larval stages (glochidia) of freshwater mussels from Europe and East Asia. We found that glochidia initially indiscriminately attached to all study host species, but immune responses elicited significant differences in host responses within 24 h of infection, which intensified during glochidial development. European bitterlings were more resistant to European glochidia and Asian bitterlings to Asian glochidia, with the strongest geographic bias in resistance in the Asian bitterling hosts. This finding suggests a strong effect of local adaptation but also indicates the non‐negligible role of coevolutionary hotspots. Low natural glochidia load on bitterling species overall hence arise from competent immune response rather than glochidia avoidance behaviour. Bitterling immune response is primarily innate and not acquired. Overall, our data demonstrate the complex outcome of parasite pressure on the evolution of host resistance, and important role of geographically structured coevolution in shaping host response.

Regeneration and colonization abilities of submerged macrophytes under different fragment types and lengths: comparison of the invasive species Myriophyllum aquaticum and the native species Myriophyllum spicatum

Abstract Alien invasive species usually have strong regeneration and colonization abilities. However, whether invasive species have advantages in term of regeneration and colonization ability over native species requires further exploration. In this study, the effects of fragment types (with and without apical tips) and lengths (5, 10, and 15 cm) on the regeneration and colonization abilities of the invasive Myriophyllum aquaticum (M. aquaticum) and native Myriophyllum spicatum (M. spicatum) in China were studied. Fragments of M. aquaticum and M. spicatum without apical tips had an advantage in branch formation, and their regeneration ability was stronger than that of fragments with apical tips. With longer initial fragments, the root length of M. aquaticum were longer and its colonization ability was stronger. This resulted in an increase in plant length, stem node number, and biomass, with an increase in fragment length. But the colonization ability of M. spicatum do not stronger with longer fragment. On the whole, native M. spicatum had stronger regeneration and colonization abilities than the invasive species M. aquaticum. However, M. aquaticum had a higher survival rate and plant length, enabling it to quickly occupy living spaces. Our results suggest that management needs to strengthened for both M. aquaticum and M. spicatum to avoid biological invasion.

Invisible dynamics: exploring the genetic diversity of peacock bass in Brazil

In Brazil, the introduction of non-native species into freshwater environments, such as peacock bass (Cichla spp.), was driven by aquaculture and sport fishing. These Amazonian fish possess phenotypic plasticity and resilience that facilitate their invasion and establishment in new habitats. Due to the taxonomic complexity of cichlids, studies on intraspecific variation are essential to mitigate the impacts of biological invasions. This study aimed to analyze the genetic diversity of peacock bass, assessing how invasive populations have diversified over time and across different regions in Brazil. Samples were collected from different invasive populations in Maranhão, São Paulo, Paraná, and Goiás. DNA was extracted and the 16S and COX1 genes were amplified. Ninety-seven specimens of the genus Cichla Schneider, 1801 were identified as Cichla monoculus Agassiz, 1831 (n=12); Cichla kelberi Kullander and Ferreira, 2006 (n=75); and Cichla piquiti (Kullander and Ferreira, 2006) (n=10). Sixteen 16S haplotypes (445bp) were identified, with haplotype diversity and nucleotide diversity values of Hd: 0.830 and Pi: 0.03777, respectively. The results showed proximity between the invasive populations from Maranhão and São Paulo, with haplotype sharing among Parque Nacional dos Lençóis Maranhenses, Baixada Maranhense, and Ilha Solteira. This highlights the fragility of species delimitation and definitions within the group, based solely on morphological data. By evaluating the set of morphological and genetic data, we found significant intraspecific variations, despite expecting population homogeneity due to the founder effect and bottleneck commonly observed in invasive populations. This underscores the adaptive potential of these cichlids.

Stage dependence of Elton's biotic resistance hypothesis of biological invasions.

Elton's biotic resistance hypothesis posits that species-rich communities are more resistant to invasion. However, it remains unknown how species, phylogenetic and functional richness, along with environmental and human-impact factors, collectively affect plant invasion as alien species progress along the introduction-naturalization-invasion continuum. Using data from 12,056 local plant communities of the Czech Republic, this study reveals varying effects of these factors on the presence and richness of alien species at different invasion stages, highlighting the complexity of the invasion process. Specifically, we demonstrate that although species richness and functional richness of resident communities had mostly negative effects on alien species presence and richness, the strength and sometimes also direction of these effects varied along the continuum. Our study not only underscores that evidence for or against Elton's biotic resistance hypothesis may be stage-dependent but also suggests that other invasion hypotheses should be carefully revisited given their potential stage-dependent nature.

Characterization and functions of temperature stress-associated microRNAs in invasive insect Bemisia tabaci Mediterranean cryptic species

With the development of international trade and frequent personnel exchanges, biological invasion is showing a rapidly growing trend worldwide. Insects are ectothermic animals, so their geographical distribution is due largely to their high and low temperature tolerances. To study the temperature response mechanisms of Bemisia tabaci MED cryptic species, miRNA-seq technology was used to unravel the miRNA library of B. tabaci MED in three field populations (TP, HB, and HK) from cities with different environmental temperatures. We identified 12 differentially expressed miRNAs in response to temperature stress, and Bta-miR-998 and Bta-miR-129 were shown to be associated with temperature tolerance. In addition, we predicted and verified the target genes associated with the temperature tolerance imparted by Bta-miR-998 and Bta-miR-129. The results showed that the down-regulated target gene of Bta-miR-129, BtMGAT3, significantly reduced the heat tolerance and another down-regulated target gene, BtRGS7, affected the cold tolerance of B. tabaci MED. These results indicate that gene expression regulated by miRNAs is an important temperature response mechanism in B. tabaci MED. This study reveals the important regulatory role of miRNA in insect temperature adaptation and provides a new avenue for studying the regulation of insect gene expression by miRNA.

Rock outcrops as interglacial refugia for plants: Ecological evidence from the forest‐steppe transition of Patagonia

AbstractIn the forest‐steppe transition of Patagonia from Argentina, the intense physical variability promotes the occurrence of contrasting vegetation units, among which is the saxicolous meadow developed on rock outcrops. In temperate and tropical regions, these geoforms of highly variable climate and topography, and poor soil development play an ecological and evolutionary role disproportionate to their reduced area. In Aguas Frías (38°46′S, 70°54′W), the range, diversity, density and adaptation of vascular plant species growing in the saxicolous meadow were compared to those of the surrounding steppe, forest and hygrophilous meadow. We hypothesize that rock outcrops exhibit a compositionally and functionally divergent, cold‐adapted flora of a previously more widespread distribution, allowing them to be categorized as refugia for species whose range retreated during the current interglacial. In comparison to the other units, the saxicolous meadow exhibited a small area, low plant cover, high total, native and rare species richness, high density and diversity of species, high richness of unique families and species and an exclusive presence of (rock) ferns. It also presented a high richness of endemic species with more extreme latitudinal and altitudinal distribution, particularly >46° S and >3000 m a.s.l. The similarity of species between the saxicolous meadow and the other units was low. Chamaephytes and nanophanerophytes were dominants, hemicryptophytes and geophytes were infrequent and mesophanerophytes and therophytes were absent. Equivalent results in terms of area of rock outcrops, and origin, strategy, composition, diversity and range of species were found in different regions. The biological and physical attributes would allow these outcrops to be characterized as reduced habitats of high diversity which could be acting as refugia for cold‐adapted plants. Conservation actions must prevent and mitigate the effects of fire, biological invasion and cattle grazing that represent the current threats to this ecosystem.

Urbanization-associated range expansion genetically homogenizes a butterfly species

Human-induced environmental change and globalization facilitate biological invasions, which can lead to the displacement of native species by non-native ones.1,2,3,4 Analogously, biodiversity loss may occur within species when habitat modifications facilitate the expansion of a specific population's range, leading to genetic admixture with native local populations. We demonstrate such intraspecific loss in population-level diversity in the Southern Small White (Pieris mannii), an originally sedentary butterfly5 that recently expanded its range across Central Europe due to urbanization.6,7,8 Using genome-wide markers from historical museum specimens and contemporary samples, we identify a distinct population initiating this expansion and reveal the genetic homogenization of native local populations by admixture with the expansive one. Our study illustrates how human-made environmental change can simultaneously benefit a species by permitting range expansion and drive cryptic biodiversity loss through the genetic homogenization of conspecific populations.

Environmental DNA-Based Identification of Non-Native Fish in Beijing: Diversity, Geographical Distribution, and Interactions with Native Taxa.

Rapid urbanization and its associated human activities have facilitated the colonization and spread of non-native species, rendering urban ecosystems, particularly in megacities such as Beijing, highly susceptible to biological invasions. This study employed environmental DNA (eDNA) metabarcoding to evaluate the biodiversity and geographical distribution of non-native fish, as well as their interactions with native fish species, across three river basins in Beijing pertaining to the Daqing River, the North Canal, and the Ji Canal. Across all the 67 sampling sites, we identified 60 fish taxa, representing 11 orders, 23 families, and 40 genera, with an average of 33.0 taxa per site. Of these, 40 taxa were native, accounting for only 47.1% of the historically recorded native fish species. Additionally, we detected 20 non-native fish taxa, spanning 11 orders, 13 families, and 17 genera. Native fish exhibited geographical homogenization across the basins, while non-native taxa displayed varied geographical distributions. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) revealed no significant variation in the non-native communities across the river basins. Although most of the non-native taxa were widespread, some were restricted to specific sites or basins. The North Canal exhibited significantly lower non-native biodiversity compared with the Ji Canal across all alpha diversity indices. Simple linear regression analyses indicated positive correlations between the number of taxa and species richness for both native and non-native taxa. Interestingly, species co-occurrence analyses revealed predominantly positive interactions among both native and non-native species pairs, with only two negative relationships involving one native and two non-native taxa. This study provides insights into the biodiversity and geographical distribution of non-native fish in Beijing and establishes a baseline for future biomonitoring and conservation efforts. The findings underscore the need for further investigation into the mechanisms and dynamics of biological invasions within urban environments in Beijing.

Assessing biological invasion predatory impacts through interaction strengths and morphological trophic profiling

AbstractBiological invasions are a major stressor on ecosystems worldwide, but tools to predict their predatory impact remain limited. Here, we quantified invader impacts using two complementary approaches: functional responses (to reveal per capita and multiple predator interaction strengths) and ecomorphology (to reveal trophic profiles and competitive overlap). We compared Mozambique tilapia Oreochromis mossambicus, a native southern African cichlid, and a near-trophically analogous invasive congener, the Nile tilapia Oreochromis niloticus. Both Nile tilapia and Mozambique tilapia exhibited a potentially prey population destabilizing Type II functional response. In both single and multiple predator pairings, invasive Nile tilapia had significantly greater prey consumption rates than native Mozambique tilapia, and thereby a greater predatory impact than its native congeneric. Attack rates were greater for Nile tilapia than Mozambique tilapia, with both species showing more similar handling times and maximum feeding rates. No evidence for multiple predator effects was detected within or between these species, and therefore impacts of both species increased additively in the presence of conspecific or heterospecific competitors. Morphological trait analyses found general differences between these two species, with the invasive Nile tilapia having distinctively larger lower jaw closing force, gill resistance and gill raker length, which facilitated greater feeding capacities over the native species. Trophic profiles predicted using morphological trait differences showed high dietary overlap and served as evidence for potential exploitative competition between the two species. These results reveal superior interaction strengths and ecomorphological trait profiles of an invasive over native species which could influence impact and native species replacement dynamics. Novel applications of functional response and ecomorphology provide complementary insights into predatory and competitive impacts from invasive species, aiding impact prediction across environmental contexts.