Pantelleria is a volcanic island located in the Sicily Channel (Italy), between Sicily and Tunisia. The island, designated a National Park in 2016, hosts an interesting vascular flora of over 600 species including 9 narrow endemics. The island’s incredible biodiversity is, however, at risk due to anthropogenic influences, climate change, and, recently, the presence and spread of alien plant species. The Pantelleria alien flora has never been thoroughly investigated, probably because many non-native species were not yet present or so widespread on the island. Now, however, with the increased general awareness of the risks associated with invasive alien species, documentation of the presence of non-native species has been steadily increasing. In this study, field and literature research was carried out to investigate the alien flora of the island. Here, we report the status of a number of non-native plants with known invasive potential. Cenchrus setaceus (=Pennisetum setaceum) is reported for the first time as naturalized in the island with clear invasive behaviour, while, particularly remarkable for their invasive potential are other studied plants such as: Acacia saligna, Ailanthus altissima, Boheravia coccinea, Carpobrotus edulis, Leucaena leucocephala subsp. glabrata, Malephora crocea, Melia azedarach, Nicotiana glauca, Opuntia ficus-indica, Parkinsonia aculeata, Washingtonia robusta and a few others less important at the moment, but to be monitored. Although most taxa showed a relatively limited distribution, the trend is to observe an increased invasiveness, which indicates that they can potentially become invasive in Pantelleria as well in the next years or decades. Their limited current distribution suggests that these species are in the early stages of the general invasion curve, when intervention is feasible and most likely to succeed. Therefore, it is most prudent to prioritize management for as many potentially problematic nonnatives as possible, which will contribute greatly to the conservation of native species and ecosystems of Pantelleria. Prevention and management of invasive non-native species—both future arrivals and those already present—are necessary to preserve the peculiar volcanic landscape of Pantelleria, which was shaped by man over the last millennia.

Increasing worldwide rates of plant introductions is an environmental issue that makes necessary to continuously update alien checklists. The Balearic Islands (an archipelago located in the Western Mediterranean basin) has been strongly influenced by tourism during the last decades, causing an increase of alien species arrival. After two years of field surveys (2021–2022), here we report and discuss the presence of 12 alien plant species previously unknown for the Balearic archipelago. Species records include the known invasives Tradescantia fluminensis, Cylindropuntia tunicata and Erythrostemon gilliesii. World widespread and of variable invasiveness Salpichroa origanifolia, Portulacaria afra, Buddleja madagascariensis, and less recorded Aloiampelos ciliaris, and Aloe x delaetii, Dracaena draco and Justicia adhatoda. Finally, Euphorbia canariensis and Sedum multiceps, both rarely recorded being these records the second and third observations outside their native range.

In 2019, Lespedeza cuneata (Chinese bushclover), a subshrub native from Afghanistan to Japan, tropical Asia and eastern and southeastern Australia, was included in the second update of the EU Regulation 1143/2014. As a consequence, it is subject to restrictions on keeping, importing, selling, breeding and growing, although it should be noted that it had not been recorded in the wild so far in the European Union. In 2022, this species was recorded on the banks of the Vesdre river in Goffontaine in the easternmost part of Belgium. Details about this first European record are presented. In compliance with the Regulation, the single individual found was removed.

Koenigia divaricata (L.) T.M. Schust. & Reveal [syn. Polygonum divaricatum L.; Aconogonon divaricatum (L.) Nakai; Persicaria divaricata (L.) H. Gross], a perennial herb of Polygonaceae, is native to temperate Eastern Asia and usually occurs in steppes, dry meadows and thickets. In recent decades, the expansion of the species to the west and north of its native range has been observed. Moreover, it was introduced to Western and Southern Siberia and Europe. The naturalisation of K. divaricata was confirmed in some countries of Northern Europe and some parts of Russia (the European part of it, as well as Western and Southern Siberia). In Europe, it is a rare species, known mainly for its cultivation as an ornamental or fodder plant. Within its primary and secondary range in Russia, it spreads effectively along transport routes, occupying roadsides, railway embankments and wastelands in their vicinity. In this paper, we report the first spontaneous occurrence of K. divaricata in Poland. It was found in September 2021 in Stare Opole near Siedlce, eastern Poland, and confirmed in July 2022. Photographic documentation of the species and phytosociological characteristics of its habitat are presented. Moreover, the locality of the species is mapped using the ATPOL cartogram method. Most likely, K. divaricata was introduced by rail transport. Currently, it should be treated as a casual alien species in the Polish flora. However, its naturalisation in Poland is likely due to suitable climatic conditions.

This paper expands the list of alien species of Crassulaceae that escaped from cultivation in Algeria and mainland North Africa, as a result of the discovery of two new alien species in the Skikda region (northeastern Algeria) in 2021 and 2023. Aeonium haworthii was recorded in a semi-natural habitat, the maritime cliff of the Stora region, and seems completely naturalized in this locality. Crassula ovata was recorded in an urban environment, where it colonizes balconies and roofs; at present, this species is considered to be a casual. These results are supported by field photos of both species, a distribution map and an updated list of alien Crassulaceae species reported so far from mainland North Africa (Algeria, Morocco and Tunisia).

Ramsar wetlands are known for their high ecological and economic value; however, in some cases, the indigenous species community is rapidly changing owing to the presence of invasive alien plants (IAPs). To address this issue, we conducted a plant survey of five Ramsar wetland sites on Jeju Island from August 2021 to August 2022 and constructed a list of IAP species. A total of 24 IAP plant species belonging to 13 families were identified. Species of the Asteraceae and Poaceae families, which have high seed production, high adaptability to damaged ecosystems, and a wide range of organisms, from annuals to perennials, were found to be abundant. The distribution of IAP species was consistent with the pattern expected during the early stages of IAP invasion in Korea. Additionally, a positive correlation was observed between the distance from residential areas and the number of IAP species. Wetlands not visited by people were found to be relatively intact, while those frequented by tourists and visitors were susceptible to IAPs. These results suggest that the introduction of IAP species into the Jeju Ramsar wetlands may have been the result of anthropogenic activities, such as tourism. Our study demonstrated that the introduction of IAPs into the Jeju Ramsar wetlands is in its early stages and is mainly attributable to human activity. Therefore, it is necessary to identify the invasion pathways, develop strategies to control or reduce invasion, and control the geographic expansion of these species. Our study highlights the threat of alien species to Jeju Ramsar wetlands, providing the basis for a strategy to protect these wetlands from the threat of invasive species.

Iris pseudacorus is an invasive macrophyte in wetland ecosystems around the world. In Argentina, its distribution range covers the eastern and central regions, registering its presence in protected, natural and artificial wetlands. We report its presence in desert natural wetlands and artificial irrigation systems (Mendoza River and Tunuyán River basins, Mendoza). We provide a description of the specimens and photographic material, adding new georeferenced records and the first specimens to scientific reference collections of drylands in western Argentina.

Since 2015, North American Douglas fir needle midges of the genus Contarinia Rondani (Diptera: Cecidomyiidae) are known to spread across Europe. In 2022, these gall-inducing insects were detected for the first time in Switzerland, where their morphological identification was confirmed by DNA barcoding. Conducting a visual monitoring of Douglas fir stands in northern Switzerland, the current distribution range was delimitated and revealed the presence of Douglas fir needle midges in forest areas close to the borders of France and Germany, where their establishment has been reported earlier. Genetic analyses of five representative populations further proved the presence of two different mitochondrial haplotypes, of which one was only found in the westernmost population, indicating faint population structuring. When assessing co-occurrence of Douglas fir needle midges with other pests and pathogens originating from North America, Douglas fir stands were often found to be infested also by the insect Adelges cooleyi (Gillette) (Hemiptera: Adelgidae) and the fungus Nothophaeocryptopus gaeumannii (T. Rohde) Videira, C. Nakashima, U. Braun, Crous (Mycosphaerellales: Mycosphaerellaceae). The observed abundance of the newly established midges within the invaded area and their co-occurrence with other introduced pests and pathogens are an indication of the increasing biotic stress level on Douglas fir, which should be taken into account when considering Douglas fir as a potential future tree species for European forests.

Here we report the establishment in Hawaiʻi of a trap-jaw ant, Odontomachus ruginodis, a species well known for its potent sting. In June 2017, a farmer on the island of Kauaʻi reported “bites” from large ants and supplied a specimen to the U.S. Fish and Wildlife Service for identification. Additional specimens were found in 2019 and 2020 in multiple locations up to 5 kilometres away from the initial detection. Multiple morphological identifications were made and combined with CO1 genetic assessment confirmed the species to be Odontomachus ruginodis, which had not been recorded prior from Hawaiʻi. We argue that greater biosecurity protocols are needed in Hawai‘i to prevent further incursions, especially the introduction of the red imported fire ant, Solenopsis invicta.

The bamboo longhorn beetle Chlorophorus annularis has been recently intercepted in several countries and becoming an emerging invasive species of concern. Here, we report the presence of C. annularis in Madagascar based on a verified specimen and citizen science data. The establishment of C. annularis in Madagascar is highly likely, given the multiple independent observations of the species at different locations within close proximity. Molecular evidence supports the morphological identification of the species, with the specimen collected in Madagascar showing closest affinity to a sample from Japan. However, due to limited samples and sequence length, further research is needed to determine the introduction pathway. We also briefly discuss the potential risks associated with the establishment of C. annularis in Madagascar and the need for coordinated actions to prevent its establishment in the country.

Helix lucorum L. (Stylommatophora, Helicidae) is one of the few European species of land snails that are currently being recorded in new localities outside their natural range. For several years there have been reports of this species being found in new localities within large European cities. In 2020, H. lucorum was found in the center of Warsaw – this is the first recorded occurrence of this species in Poland. The area of Warsaw in which the snail was discovered covers about 1.2 ha. To date, no increase in this population’s range has been detected.

The Succineidae Beck, 1837 are a family of terrestrial mollusks that are increasingly transported worldwide in horticultural trade. Succineids are extremely difficult to identify morphologically, especially if collected from locations beyond their native range and in the absence of knowledge of their native provenance. In this study, we report an unidentified species of the Succineidae in a flower bed of Petunia sp., Ariake, Tokyo, Japan. A fragment of the mitochondrial cytochrome oxidase subunit 1 (COI) gene was sequenced, and the shell and genital morphologies were compared with those of other similar species. This is the third succineid species introduced in Japan, as a species found in the field.

Invasive species, including many polychaetes, are one of the major factors affecting the diversity of the Mediterranean ecosystems. Coastal lagoons, as transitional ecosystems, present a large spatial and temporal variability that makes them suitable for opportunistic species colonization. In this work, the species Leodamas australiensis (Hartmann-Schröder, 1979) has been identified in the Mar Menor coastal lagoon (Spain) and this is its first report from the Mediterranean. It is characterized by the presence of large aciculae with protruding and distinctly curved tips in abdominal neuropodia and by the onset of dorsal branchiae on chaetiger 6. Molecular analyses were carried out using mitochondrial 16S rDNA gene sequences. The spatio-temporal distribution of L. australiensis and its relationship with other species belonging to the family Orbiniidae in the lagoon was investigated in different periods from 1982 to 2018. This species expanded from sites more connected to the Mediterranean Sea towards more confined areas of the basin. However, this expansion did not affect in an appreciable manner to native orbiniids. Follow-up studies at longer time scales are needed to determine if L. australiensis is a casual presence or maintains a well-established population.

The penaeid shrimp Penaeus aztecus Ives, 1891 has been collected off the Catalan coast for the first time. This represents the first report of the species for the Iberian Peninsula waters. Its morphological description, as well as the DNA sequenced fragment, agree with the descriptions assigned to Penaeus aztecus. This constitutes the first record of the species in the Spanish Mediterranean coast and the confirmation the species westward expansion along the Mediterranean Sea probably been drifted from the later invasion in the Gulf of Lions.

A single Blue swimming crab Portunus segnis was captured on November 5th 2022 close to the harbor of Ancona, off the central Adriatic coast (Italy) by artisanal fishers. Taxonomic comparisons were performed with collection materials, which also included two unreported specimens of the species from the Ionian coast of Calabria, Italy. The large distance between the Adriatic record of P. segnis and its invasion front, reinforces the hypothesis that human-mediated translocations contribute to the secondary dispersal or introduction of this invasive species in Mediterranean waters.

The introduction of non-indigenous species to aquatic ecosystems is one of the main threats to global biodiversity. This paper reports the occurrence of the blue swimmer crab Portunus segnis in southwestern European waters (i.e., the Gulf of Cadiz). We discuss the invasive potential of P. segnis and possible mechanisms of its expansion into this new region. The detection of this species also highlights the importance of involving citizen scientists in the reporting of non-indigenous species.

Exotic species introductions are a major threat to biodiversity. The first step to their control involves identifying their presence, distribution, and impacts on native species and their habitats, especially in highly diverse regions. We update and document new records of exotic freshwater fauna from the Baja California Mediterranean region. We found 157 locality records of 17 exotic aquatic species; 16 genera and 15 families were recorded. Five species are new records for the region: Malaysian trumpet snail (Melanoides tuberculata), black bullhead catfish (Ameiurus melas), common carp (Cyprinus carpio), spiny softshell turtle (Apalone spinifera), and red-eared slider (Trachemys scripta). The catfish, carp, and softshell turtle have been previously reported from Baja California, but only from the Colorado River and adjacent Mexicali Valley, while the snail and slider represent new state records. Of the 157 locality records, 71 were found in published literature and 86 represent new records from field observations, collected specimens and citizen science observations. Based on discussions with local ranchers and landowners, some exotic species were introduced for food or aesthetic purposes, emphasizing the need for environmental programs to stop these actions.

The occurrence of the alien freshwater planarian Girardia sinensis Chen & Wang, 2015 is reported for the first time in sub-Saharan Africa. This species is a global invader of freshwater bodies as evidenced by its very recently reported discoveries in Europe, Asia and Australia. We used DNA barcoding and phylogenetic analysis to confirm species identity, as morphological identification alone is not accurate. Unintentional introduction via the aquarium trade through contamination is considered a possibility. Taken together with other reports of recent introductions of invasive freshwater species in South Africa, possibly through aquarium trade, this raises serious concerns about the ineffective control of aquarium trade.

Asian clam, Corbicula fluminea, is an invasive mollusk species (Bivalvia, Veneridae) known to cause several negative impacts in freshwater ecosystems where it has been introduced. In the 2022 summer season a total drying up took place in the “Torre Flavia” wetland, a Special Protection Area (Latium, central Italy): it made possible a survey of biological remains deposited in the bottom of the wetland channels (> 2,000 m in total length). During this survey, for the first time, we recorded valves belonging to 68 specimens of Asian clam. We did not record living specimens. This is the first case of occurrence of this mollusk in a wetland basin (the fourth record for Central Italy). The population would not appear to have naturalized locally but, probably, individuals could be accidental arrived by the waters pumped by the Reclaimed Agency. We discussed the implications about the role of these Agencies in favour involuntarily the translocation of both native and non-native species from the dewatering pumps (along the Tiber River) to surrounding land reclaimed wet areas (channels and swamps) and croplands connected to the artificial water system.

This paper reports the first records of Cercopagis pengoi in the Mississippi River Basin, Illinois, USA. In 2017, a total of 11 C. pengoi were collected from two different locations during zooplankton sampling in the Illinois Waterway. One location was in the Chicago Sanitary and Ship Canal and the second location was in the Calumet-Sag Channel, approximately eight and 35 river kilometers from Lake Michigan, respectively. In 2021, eight additional individuals were encountered in ichthyoplankton samples collected in the Chicago Sanitary and Ship Canal, three river kilometers upstream of the 2017 capture location. The extent and density of C. pengoi within the Illinois Waterway is currently unknown; therefore, additional sampling is warranted to better understand their distribution and abundance to facilitate an assessment of the risks of spread to other connected waterways.

Non-native aquatic species have caused profound ecological and physical impacts in many waterbodies, and in China many non-native species are known for their ecological displacements and the changes they have induced in a diversity of wetland categories. Water lettuce (Pistia stratiotes), a free-floating aquatic vascular plant native to South America, is a highly invasive species that has been introduced in Europe, North America, Africa, Asia, Central America and the Caribbean. This species was brought to China over 500 years ago, and it has become a widespread and aggressively invasive species. A lack of biological and ecological information has limited the effective management and control of this invasive species in China. Through field investigations and a literature review we present water lettuce’s pathway of introduction (as a medicinal herb and its use in artificial wetlands), its capability to colonize and establish feral populations, its distribution in China (Eastern and Southwest of China), and its ecological and societal impacts. We hope that this study can provide useful information for the management of this species and other non-native aquatic plants in China.

Faxonious propinquus is considered native to the Susquehanna River watershed but is not native to the nearby Delaware River watershed in North America. Here we show that Faxonious propinquus is now established in the Delaware River watershed, which is reason for concern. We also provide published records to describe more fully the distribution of Procambarus acutus, a species considered non-native in the Delaware River when found upstream of the Atlantic Coastal Plain. We provide evidence that indicates that F. propinquus has become established in the Lehigh River, a subwatershed in the Upper Delaware River, and that P. acutus has expanded into this portion as well. In addition, we provide evidence of hybridization occurring between the native Faxonius limosus and a non-native congener.

Invasive species are a significant challenge for freshwater ecosystems on a global scale. They can cause serious ecological and economic damage. The aim of our research was to document the range expansion of freshwater invasive fishes in Georgia. Fish studies were conducted during the years from 2019 to 2022 using standard methodologies. A DNA barcoding approach was also employed to validate our findings. During the course of the study, invasive sharpbelly – Hemiculter leucisculus from different locations of eastern Georgia has been detected, which is the first case of the existence of this species in the country. In addition, we document a significant range expansion of two other non-native species in Georgia. Amur goby, Rhinogobius lindbergi, was collected in western Georgia, which was previously known only from eastern Georgia, and the occurrence of mosquitofish, Gambusia holbrooki, was confirmed in east Georgia for the first time. It is expected that the rapid expansion of the range of the mentioned species may lead to a decrease in local and endemic species populations in Georgia. With the development of aquacultural activities in the country, these risks will also increase.

Global amphibian populations are declining, and invasive fish are known to impact many threatened species. South Africa has both a biodiverse amphibian fauna and a rich history of invasive fish introductions with high establishment success. Studies have identified some preliminary evidence for negative impacts of invasive salmonids on two ghost frog species (Anura: Heleophrynidae). This study aims to investigate whether these negative impacts previously reported are reflected across a broader scale. Tadpoles of two species, Heleophryne regis and H. purcelli were sampled in the presence and absence of invasive fish at 111 sites across 26 streams in the Western Cape province of South Africa. A generalised linear mixed model showed invasive fish to have the most significant negative effect explaining tadpole abundance. Mean tadpole abundance decreases by 18 times in the presence of invasive fish. Environmental variables with significant effects on tadpole abundance include pH, oxygen saturation, temperature, stream depth and non-native riparian vegetation type. We also define an environmental niche of ghost frog tadpoles which does not differ between species. We conclude that invasive fish have significant negative impacts on ghost frog tadpole abundance, but the effect of the environment should not be overlooked in amphibian conservation planning and invasive species management decisions. This study supports the removal of invasive fish and alien vegetation to improve the conservation of ghost frogs.

Nichols’ common goby Rhinogobius cliffordpopei (Nichols, 1925) is a small-bodied benthic carnivorous fish, and native to central and southeast China. Due to the interregional commercial exchanges of aquaculture and aquatic trade, it has widely introduced numerous water bodies outside the original range in China, but has not been found in Tibet. During a fish survey in May 2022, we collected 22 individuals of R. cliffordpopei, including five juveniles, from four sites in the Yarlung Zangbo River in Tibet. This finding suggests that R. cliffordpopei has established wild populations in the Yarlung Zangbo. To protect the endemic species, government departments should strictly limit the release to reduce the potential risks of non-native species.

The North American western mosquitofish, Gambusia affinis (Baird and Girard, 1853), has been introduced into a number of countries around the world, primarily for the control of mosquito populations. Gambusia affinis is known to harbour several monogenean parasites, which have the potential to be co-introduced to new regions. However, despite the broad non-native distribution of this fish species, their monogenean parasites have been reported from a relatively small number of locations. Parasitological investigations have identified very few freshwater monogenean parasites from freshwater fish in New Zealand. Two monogenean parasites were recorded infesting G. affinis in New Zealand; Salsuginus seculus (Mizelle and Arcadi, 1945) (a new genus to New Zealand) on the gills and Gyrodactlyus gambusiae Rogers and Welborn, 1965, on the gills and surface of the fish. Despite the broad distribution of G. affinis, S. seculus and G. gambusiae have been reported in few countries due, perhaps, to lack of research effort on monogeneans, their small size, enemy-release, or a combination of these factors. Based on the diversity of monogeneans in other countries that are found associated with fish with non-native populations in New Zealand, it is likely that many unrecognised non-native monogeneans are established in New Zealand’s freshwater ecosystems alongside their fish hosts. Further, the number of introduced monogeneans is likely to be even higher than is currently appreciated when considering non-native fish in the aquarium trade and other introduced freshwater fauna, such as terrapins.

Listing alien species is becoming more important due to the global spread of infectious diseases such as COVID-19, chytrid fungus, and ranavirus. We determined the identity and origin of newly discovered geckos (hereafter, Incheon gecko) near Incheon Port, South Korea, in September 2021, through morphological and genetic studies. The number of interorbitals of the Incheon geckos overlapped only with those of Gekko swinhonis, among four closely allied species. In addition, the cytochrome c oxidase subunit 1 (CO1, 658 bp) sequence of Incheon geckos had a close genetic p-distance (0.00–5.47%) with that of G. swinhonis in China. Furthermore, Incheon geckos shared major mitochondrial cytochrome b (Cytb, 1,140 bp) haplotypes with G. swinhonis samples collected in coastal cities along the Bohai Bay in northeast China, including Huludao, Shedao, Laiyang, and Tianjin, where regular car-ferry routes connect them to Incheon. These results suggest that the geckos, newly discovered in Incheon, South Korea, are G. swinhonis and were recently introduced from China via ocean cargo, showing a clear case of human-mediated introduction of non-native geckos.

Historical data sets are valuable for learning and developing new tools for understanding and predicting species spread and dispersal. We update the classic Ulbrich (1930) map of muskrat (Ondatra zibethicus) spread in Central Europe, converting it to a set of GIS maps. We illustrate the updated data by fitting a set of simple models that measure the rate of spread of species. We recover the classic findings of radial spread from previous studies and, with the finer-scale data, show when the traditional radial assumption of spread breaks down. We believe that our version of the Ulbrich data is a valuable tool for pedagogy and a type of digital playground for the design and development of new tools to estimate species spread and dispersal.