In Japan, trematodes of the family Ochetosomatidae are not naturally distributed. However, the introduced ochetosomatid Ochetosoma kansense (Crow, 1913) has been reported from the oral cavity of native snakes in western Japan since 2010. In this study, trematodes were isolated from the oral cavities of the native Japanese snakes, Elaphe quadrivirgata (Boie, 1826), E. climacophora (Boie, 1826), and Rhabdophis tigrinus (Boie, 1826), in the central Kanto region of eastern Japan. Morphological and molecular analyses of the isolated trematodes revealed that all trematodes were identifiable to a newly introduced ochetosomatid species to Japan, O. elongatum (Pratt, 1903), which originated from North America; Lechriorchis tygarti was synonymized with O. elongatum based on identical molecular data and morphological similarity. To identify first intermediate hosts of O. elongatum, seven freshwater snail species were examined in eastern Japan. Molecular analysis was used to identify O. elongatum sporocysts in the freshwater snail Physella acuta (Draparnaud, 1805), which also originated from North America. The other six species did not host O. elongatum, suggesting that Ph. acuta is the only first intermediate host of O. elongatum in Japan. Although O. elongatum has been detected in Japan, its invasion route and period of introduction are unclear. Frequent imports of freshwater snails and wild snakes from North America, after the 1990s and 2005, respectively, presumably introduced O. elongatum in Japan.

Population genetic analysis of invasive populations can provide valuable insights into the source of introductions, pathways for expansion, and their demographic histories. Flathead catfish (Pylodictis olivaris) are a prolific invasive species with high fecundity, long-distance dispersal, and piscivorous feeding habits that can lead to declines in native fish populations. In this study, we analyse the genetics of invasive P. olivaris in the Mid-Atlantic region to assess their connectivity and attempt to reconstruct the history of introduced populations. Based on an assessment across 13 microsatellite loci, P. olivaris from the Susquehanna River system (N = 537), Schuylkill River (N = 33), and Delaware River (N = 1) have low genetic diversity (global Hobs = 0.504), although we detected no evidence of substantial inbreeding (FIS = -0.083 to 0.022). P. olivaris from these different river systems were genetically distinct, suggesting separate introductions. However, population structure was much weaker within each river system and exhibited a pattern of high connectivity, with some evidence of isolation by distance. P. olivaris from the Susquehanna and Schuylkill rivers showed evidence for recent genetic bottlenecks, and demographic models were consistent with historical records, which suggest that populations were established by recent founder events consisting of a small number of individuals. Our results show the risk posed by small introductions of P. olivaris, which can spread widely once a population is established, and highlight the importance of prevention and sensitive early detection methods to prevent the spread of P. olivaris in the future.

High abundances of gelatinous zooplankton (GZ) can significantly impact marine ecosystem by acting as both sink and source of organic matter (OM) and nutrients. The decay of GZ bloom can introduce significant amount of OM to the ocean interior, with its variability influenced by GZ life traits and environmental factors, impacting microbial communities vital to marine biogeochemical cycles. The invasive ctenophores Mnemiopsis leidyi has formed massive blooms in the northern Adriatic Sea since 2016. However, the variability in the chemical composition and egg production of blooming populations, as well as the role of environmental factors in governing this variability, remains largely unknown. Our analysis of biometry, chemical composition, and fecundity of M. leidyi sampled in the Gulf of Trieste in 2021 revealed stable carbon and nitrogen content throughout bloom development, with no significant correlation with seawater temperature, salinity, oxygen, and chlorophyll a concentration. Although the studied population exhibited homogeneity in terms of biometry and chemical composition, the number of produced eggs varied substantially, showing no clear correlation with environmental variables and being somewhat lower than previously reported for the study area and other Mediterranean areas. We observed a positive correlation between the wet weight of individuals and the percentage of hatched eggs, as well as a significant positive correlation between the percentage of hatched eggs and ambient seawater temperature. Additionally, we noted that the speed of hatching decreased with decreasing seawater temperature in autumn, corresponding to the end of M. leidyi bloom.

Nowadays, in addition to the destruction and fragmentation of the world\'s habitats, invasive species, and damage caused by them, are one of the most important factors in the destruction of ecosystems. The raccoon (Procyon lotor) is a medium-sized mammal that is placed in mid-levels of the food web and can affect a wide range of species. Considering the damage done to local ecosystems by this invasive species, habitat assessment and determining the factors affecting its habitat suitability would be a key step in managing this species. In this study, using the MaxEnt model and examining 12 environmental parameters (elevation, slope, aspect, geological units, soil type, vegetation, land use, distance to villages, distance to main roads, distance to waterways, average temperature, and rainfall) in the west of Guilan Province, habitat suitability of this alien species was determined, and the most important factors affecting this suitability were investigated. Results showed that the validity value of the model (AUC) was estimated to be 0.852 and parameters such as distance to village (34.5%), elevation (24.2%), and land use (15.9%) are among the most important and effective factors. Also, the results showed that 0.60% of the study area has high suitability, 6.14% moderate, 24.87% low, and 68.36% unsuitable areas for raccoons. The overall result shows that despite the lack of vast favorable areas for this invasive species, an increase in the number and expansion of this species is very likely because of its omnivorous diet, high adaptability to different environments and conditions, as well as extensive niche. All of these factors cause raccoons to spread further in the region and consequently increase the risks and damages to the native ecosystem.

A 60 days study was conducted to evaluate the physiological response of indigenous species Labeo rohita (LR) and indigenous predator Chitala chitala (CC) in presence of an invasive species Piaractus brachypomus (PB). Two treatment groups as LR + PB (T1) and LR + PB + CC (T2) with individual control groups as T0LR, T0PB and T0CC were designed in triplicates. Fingerlings of LR, PB and CC were randomly distributed into 15 circular tanks with a stocking ratio of 1:1 and 1:1:0.3 in T1 and T2 group, respectively and 10 nos. each of LR, PB and CC in respective control groups. At first 15 min of the experiment, cortisol level was found significantly (P < 0.05) higher in all three experimental fishes in T1 and T2 groups. With the experimental duration, the level of stress hormone (cortisol), oxidative stress enzymes (superoxide dismutase, catalase, and glutathione peroxidase), tissue metabolic enzymes (lactate dehydrogenase and malate dehydrogenase), serum metabolic enzymes (transaminase enzymes) and blood glucose level were significantly (P < 0.05) increased in T1 and T2 groups for LR and CC whereas, no variation (P > 0.05) were observed for PB in both T1 and T2 groups. The total antioxidant capacity (TAC), liver glycogen, total protein, albumin and globulin were found to be significantly (P < 0.05) decreased in LR in the presence of PB and CC. The present study provides a preliminary insight into the biological interaction between native and invasive species and their physiological responses in the presence of native predator with higher trophic index. Thus, the results of the study suggest the superior traits of invasive P. brachypomus try to dominate the other two native species by negatively influencing the native fauna even with a higher trophic index (C. chitala).

Canada thistle is a pervasive perennial weed, causing challenges to agricultural and natural ecosystems globally. Although research has focused on the phenology, genetics, and control of Canada thistle, little is known about the rhizosphere microbiome and the role plant-microbe interactions play in invasion success. This study investigated the rhizosphere microbiome of Canada thistle across diverse climates, soils, and crops in the U.S. northern Great Plains. Soil and rhizosphere samples were collected and bacterial 16S and fungal ITS2 sequencing were performed to characterize the core microbiome and identify potential factors contributing to invasion success. Amplicon sequencing revealed a stable core microbiome that was detected in the Canada thistle rhizosphere across all locations. The core microbiome was dominated by the bacterial phyla Actinobacteriota and Proteobacteria and fungal phyla Ascomycota and Basidiomycota. Differential abundance analysis showed rhizosphere fungal communities were enriched in pathogen-containing genera with a 1.7-fold greater abundance of Fusaria and a 2.6-fold greater abundance of Gibberella compared to bulk soil. Predictive functional profiling showed rhizosphere communities were enriched (p < 0.05, FDR corrected) in plant pathogen fungal guilds which represented 19% of the fungal community. The rhizosphere microbiome was similar in composition across environments, highlighting the stable association between Canada thistle and specific microbial taxa. This study characterized the core microbiome of Canada thistle, and the findings highlight plant-microbe interactions shaping invasive behavior. These findings are important for understanding the ecological impacts of plant invasion and soil-microbe ecological processes.

Organismal invasions have repeatedly been cited as a driving force behind the loss of biodiversity. Unlike many other impacts of invasion, the effect of invasion on native symbiont communities has received less attention. The introduction of invasive hosts presents a potential opportunity to native symbionts; invasive hosts could benefit native symbionts through providing a novel host environment that improves symbiont fitness relative to their fitness on native hosts. Alternatively, invasive hosts could noncompetent hosts for native symbionts, resulting in negative impacts on native symbiont abundance and diversity. Crayfish in the northern hemisphere host diverse assemblages of obligate annelid symbionts (P: Anellida, O: Branchiobdellida). Two invasive crayfish hosts in the genus Faxonius have been introduced and are interacting with the native crayfish hosts and their symbionts in three watersheds in western Virginia, USA. Previous studies suggest that the invasive host F. cristavarius is a less competent host for symbionts compared to native hosts in the genus Cambarus. We carried out an extensive survey in these watersheds to determine impacts of varying degrees of invasion on branchiobdellidan abundance and diversity. We also conducted a complementary host replacement experiment to investigate how increases in the relative abundance of invasive hosts contributes to observed patterns of symbiont abundance and diversity in the field. In our survey, as the proportion of invasive hosts at a site increased, branchiobdellidan abundance and diversity declined significantly. In the experiment, the worms dispersed onto both native and invasive hosts. As the percentage of noncompetent F. cristavarius hosts increased, the survival of branchiobdellidans declined. Both symbiont survival and opportunities for successful dispersal are reduced as this noncompetent invasive host progressively displaces native hosts, which imperils the integrity of native host-symbiont systems. Given that many native hosts accrue significant fitness benefits from their relationships with native symbionts, including hosts in our study system, losses of beneficial symbionts may produce a positive feedback loop that decreases invasion resistance of native species, exacerbates the effects of invasions, and presents a major conservation issue in invaded systems.

Vegetation cover has been consistently reported to be a factor influencing soil biota. Massive spreading of invasive plants may transform native plant communities, changing the quality of habitats as a result of modification of soil properties, most often having a directional effect on soil microorganisms and soil fauna. One of the most numerous microarthropods in the litter and soil is Acari. It has been shown that invasive plants usually have a negative effect on mites. We hypothesized that invasive Spiraea tomentosa affects the structure of the Uropodina community and that the abundance and species richness of Uropodina are lower in stands monodominated by S. tomentosa than in wet meadows free of this alien species. The research was carried out in wet meadows, where permanent plots were established in an invaded and uninvaded area of each meadow, soil samples were collected, soil moisture was determined and the mites were extracted. We found that Uropodina mite communities differed in the abundance of individual species but that the abundance and richness of species in their communities were similar. S. tomentosa invasion led primarily to changes in the quality of Uropodina communities, due to an increase in the shares of species from forest and hygrophilous habitats. Our results suggest that alien plant invasion does not always induce directional changes in mite assemblages, and conclude that the impact of an alien species on Uropodina may cause significant changes in the abundance and richness of individual species without causing significant changes in the abundance and diversity of their community.

BACKGROUND: The spread of Vespa velutina Lepeletier, 1836 (Asian hornet) in South Korea poses a threat to biodiversity and agriculture. Traditional species interaction models often fail to capture the complexity of invasive species dynamics. This study used association rule learning (ARL) and clustering analyses to explore the interactions of V. velutina with native Vespidae species in South Korea, with the aim of uncovering patterns of coexistence and competition.
RESULTS: Over 4 years (2020-2023), 304 traps were strategically placed across South Korea to collect data on Vespidae species. Our findings showed that Vespula flaviceps, Vespa crabro, and Vespula koreensis were the most frequently encountered species. V. velutina was also widespread, suggesting its successful integration into local ecosystems. The ARL analysis, using the \'apriori\' algorithm, identified significant co-occurrence patterns and potential interactions. The rules generated indicated both competitive and coexistent relationships with varying levels of association strength across different regions. Clustering analyses, including hierarchical and k-means clustering, grouped species based on their occurrence similarities. The distinct clusters formed in the analysis highlighted the unique ecological roles and interactions of V. velutina and other Vespidae species in South Korean ecosystems.
CONCLUSIONS: This study confirms the successful establishment of V. velutina in diverse South Korean ecosystems and highlights its complex interactions with native species. These findings support the need for nuanced management strategies that consider the intricate ecological relationships of V. velutina. This approach is crucial for the effective management of invasive species and ecosystem conservation. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The release of biological control agents has been an important means of controlling invasive species for over 150 years. While these releases have led to the sustainable control of over 250 invasive pest and weed species worldwide, a minority have caused environmental harm. A growing recognition of the risks of biological control led to a focus on risk assessment beginning in the 1990s along with a precipitous decline in releases. While this new focus greatly improved the safety of biological control, it came at the cost of lost opportunities to solve environmental problems associated with invasive species. A framework that incorporates benefits and risks of biological control is thus needed to understand the net environmental effects of biological control releases. We introduce such a framework, using native biodiversity as the common currency for both benefits and risks. The model is based on interactions among four categories of organisms: (1) the biological control agent, (2) the invasive species (pest or weed) targeted by the agent, (3) one or more native species that stand to benefit from the control of the target species, and (4) one or more native species that are at risk of being harmed by the released biological control agent. Conservation values of the potentially benefited and harmed native species are incorporated as well, and they are weighted according to three axes: vulnerability to extinction, the ecosystem services provided, and cultural significance. Further, we incorporate the potential for indirect risks to native species, which we consider will result mainly from the ecological process of agent enrichment that may occur if the agent exploits but does not control the target pest or weed. We illustrate the use of this framework by retrospectively analyzing the release of the vedalia beetle, Novius (= Rodolia) cardinalis, to control the cottony cushion scale, Icerya purchasi, in the Galapagos Islands. While the framework is particularly adaptable to biological control releases in natural areas, it can also be used in managed settings, where biological control protects native species through the reduction of pesticide use.