Gleditsia triacanthos (Leguminosae) is a deciduous tree native to the Eastern USA. The first invasive record of G. triacanthos in the Iberian Peninsula is here reported. The invaded area (Guadiamar river, southern Spain) is under a Csa climate type, which is an infrequent and unexpected type for that species to behave as invasive. The analysis of trunk perimeters and of the spatial distribution showed a net recruitment and an invasive trend throughout the temporary stretch of the river.

First reports of pheretimoid earthworms in Atlantic Canada, from a suburban site in south-central New Brunswick, are documented. Pheretimoids were present at high densities under hardwood cover, estimated at ~ several hundred per m^-2 in the small area sampled. Preliminary samples collected at the site in October 2021 suggest that Metaphire hilgendorfi, followed closely by Amynthas tokioensis, were dominant, while A. minimus was rare. The latter is the first report of A. minimus from Canada. Associated lumbricids, present in much smaller numbers and in descending order of abundance, included Lumbricus rubellus, Dendrobaena octaedra, and Aporrectodea tuberculata. We suggest that pheretimoid earthworms are probably more widespread in the Atlantic Canadian region than this first report would indicate. Further survey, supported by public education and reporting, will be required to assess the full ecological impact of invasive Asian pheretimoids in eastern Canada.

The various problems caused by invasive species have become more serious in recent years, and thus it is important to discuss their identifications and invasion processes. Phylogenetic and population genetic methods are effective tools for solving these problems. Some land snails, including the genus Macrochlamys, have invaded and established themselves worldwide as invasive species. In this study, we identified the species of Macrochlamys sp. from Japan and estimated their invasion pathways to Japan. Phylogenetic analysis showed that the Japanese snails were closely related to Macrochlamys indica from Bangladesh and West Bengal. Population genetic analysis also revealed that most of the Japanese snails were concentrated in single haplotype and were close in genetic distance. Detailed anatomical investigation of genitalia and oral organs showed morphological similarities between the Japanese and Bangladeshi snails, supporting the results of the phylogenetic analysis. These findings suggest that the Japanese Macrochlamys sp. is recognized as Macrochlamys indica and may have been introduced from the vicinity of Bangladesh and West Bengal and subsequently spread within Japan.

The widespread tropical tramp snail Gastrocopta servilis is recorded for the first time in South Africa. This represents the first record of the species from the continent of Africa. Specimens found in abundance in a remnant of natural habitat in Durban in 2011 could not be identified with any indigenous or introduced species known from eastern South Africa, suggesting that the species involved may represent an unrecorded introduction. Subsequent morphological study led to the material being identified as G. servilis. This identification was confirmed by comparison of sequence data from the mitochondrial DNA cytochrome c oxidase subunit I gene obtained for this material with that of other Gastrocopta species. Although this is the first record of the species from the seaboard of the western Indian Ocean, it is likely that other Gastrocopta species described from islands in this region are in reality pseudoindigenous taxa representing further introduced populations of the globally widespread G. servilis.

The little fire ant, Wasmannia auropunctata is an invasive species native to Central and South America. We report the establishment of this species in Taiwan, which is also the first confirmed population in the East Asian region. Little fire ants were found at two locations in central Taiwan, separated by approximately 30 km. Genetic and behavioral analyses indicated that the two populations both employ clonal reproduction and showed no aggression towards each other. Results of population genetic analyses indicate that the two populations are most likely derived from a common source population or genetically similar populations.

Ladybird beetles (Coccinellidae) were collected at 11 sites on the island of Madeira from 4th to 10th of February 2020. Eight species non-indigenous to Madeira were recorded, and two of them, Olla v-nigrum and Cryptolaemus montrouzieri, have not previously been reported from the Madeira archipelago. This study also confirmed that Harmonia axyridis, a highly invasive species with an almost global range, has established on the island. According to the literature data and results of this study, 42 species of Coccinellidae have so far been documented to occur in the Madeira archipelago, including nine non-indigenous species of Afrotropical, Asiatic, Australian, and American origin. Comparison of available data on non-indigenous Coccinellidae recorded in different archipelagos of Macaronesia shows that Madeira has the richest fauna of those non-indigenous species. The percentage contribution of the non-native species to the fauna of Coccinellidae of different Macaronesian archipelagos ranges between 12% (Cape Verde) and 21% (Madeira) and is higher than that reported for the mainland areas in SW Europe (6.5–7%). This study supports the island susceptibility hypothesis.

The Asian lady beetle, Harmonia axyridis (Pallas), is native to Asia and was introduced to many locations for biocontrol thanks to its voracious nature. H. axyridis was identified in multiple different locations, indicating a high level of invasiveness, and was shown to compete with local species. Here we report the first molecular identification of H. axyridis in Israel.

In the last decade, the American cherry fruit Rhagoletis cingulata has become an important pest of cherry crops in many temperate regions of Europe. Native to North America, this fruit fly species was introduced in Europe in the 1980s. It was first described in Switzerland in 1983, and since then populations have been detected in the Netherlands, Hungary, and Germany. The risk this widespread invasive fly poses to native cherry crops is considerable. Here we show, using molecular markers, that R. cingulata is present in Lithuania, and that this region is the most northerly eastern region where populations of this invasive fly are found to date. Moreover, it is also shown that the native cherry fruit fly R. cerasi and the invasive fly share at least one parasitoid species in the region, which could contribute to population suppression of the invasive pest. This work shows that this invasive fruit fly is expanding farther east, and systematic monitoring in the western part of the East European Plain should be performed to prevent damage by this pest species.

Aphids are phloem sap-feeding insects distributed worldwide that can cause serious crop production losses, especially in temperate regions. Biological invasion by aphids is common, and the accumulation of case reports is important for their control. Here, we provide the first report of the cedar bark aphid Cinara cedri cedri (Hemiptera: Aphidoidea) in Japan. In Okazaki City, Aichi Prefecture, and Nishinomiya City, Hyogo Prefecture, we found this species on twigs of ornamental trees, Cedrus deodara. These two collection localities are clearly distant from the region of known distribution of this species. Cinara cedri cedri is native to the East Mediterranean region and has been introduced into several European countries, the USA, Canada, and Korea. The mitochondrial COI sequences of the Japanese populations matched the identity of those in the USA and Canada, recently introduced populations, and some European populations. Wolbachia is an endosymbiont of this species, and we found that those infected in the Japanese population of C. cedri showed no variation in 16S rDNA sequences. The sequences were identical to those of one of the two Wolbachia strains detected in the native ranges of C. cedri. We observed C. cedri populations from early summer to late winter in 2021 and early summer in 2022 in both localities, indicating that these aphids are able to overwinter in Japan.

The brown macroalgae Rugulopteryx okamurae is described as one of the most severe and threatening invasive marine macroalgae in European waters. This study reports the first record of R. okamurae in the Madeira archipelago, which represents a new southern distribution limit of this species in NE Atlantic European waters. Morphological and molecular characters were used to confirm the species' identity, and its potential invasion risk in Madeiran waters was screened using the standard risk assessment tool AS-ISK. Results show that R. okamurae has a medium-high risk of becoming invasive in Madeira Island under present and future climate scenarios. The greater risk of impact involves suppressing local species growth and the modification and degradation of local habitats, including trophic cascade effects. However, environmental and commercial impacts could also occur in case of an explosion of the invasive populations. This new introduction in Madeira coastal waters emphasises the need for regular monitoring of R. okamurae, particularly to assess population dynamics to avoid establishing and further expansions. Finally, we recommend the evaluation of the possible derived impacts affecting rocky coastal communities and adopting the necessary mitigation measures and policies.

The Mediterranean Sea is one of the main hotspots for the introduction of nonindigenous species in the world. The invasive alga Rugulopteryx okamurae was detected in 2015 along the coasts of the Strait of Gibraltar, the Atlantic entrance to the Mediterranean Sea. This brown seaweed of Asian origin, with an enormous expansion capacity and high survival rate, has spread rapidly across the Alboran Sea (western Mediterranean). Nevertheless, this species continues to show its highest abundance in areas close to the Strait of Gibraltar. We recorded R. okamurae in Punta de la Mona (Granada, northern coast of the Alboran Sea), one of the zones with the highest marine biodiversity in the Alboran Sea. This record is the easternmost point within the Spanish coasts where abundance data for this invasive species are available. Rugulopteryx okamurae demonstrated its highest abundance values at 48 m, an unusual record for this species in the Mediterranean Sea. We found R. okamurae growing on rocky bottoms, multiple coralligenous organisms, artificial substrates and epiphyting the coral Dendrophyllia ramea (an important habitat-forming species). Cold-water corals provide substrate, shelter and habitat for other species and play a critical role in deep water ecosystems. It is crucial to study and quantify the possible effects of invasive species on habitat-forming species, especially in the Mediterranean Sea, where the arrival of exotic organisms is striking; a better understanding of their dispersal capacities is urgently needed, as they can affect key organisms. The results obtained in this study validate the prolific capacity of R. okamurae to colonize new areas, affecting both littoral and deeper coastal areas. This behaviour, coupled with the ability to grow on a wide variety of suitable substrates, creates a strong threat to natural environments.

Ascidians are sessile marine invertebrates and many are invasive. One notorious example is the solitary species Microcosmus squamiger, which has spread from a hypothesized native region in southeastern Australia to temperate waters worldwide and is considered a global marine invader. This study is the first report of M. squamiger from Jeju Island, South Korea. We collected specimens (N = 20) from Unjin and Wimi harbors on Jeju Island and dissected them to characterise their siphons, pharynx, and dorsal tubercle using stereomicroscopy and scanning electron microscopy. The shape of the dorsal tubercle (the peritubercular area filled with two spiral coils) and the length (15–20 µm) and shape (roof tile or fingernail) of the siphon spine were consistent with previous identifications of the species. Additionally, molecular verification was performed by extracting genomic DNA from four specimens, two each from Unjin and Wimi harbors. By sequencing a section of the mitochondrial cytochrome oxidase subunit I gene and analysing the generated sequences using a maximum likelihood-based phylogenetic tree, we compared to individuals previously identified as M. squamiger and confirmed the existence of two clades. Therefore, the presence of M. squamiger was verified by morphological and phylogenetic identification. Although M. squamiger is currently distributed globally (except in Antarctica), records from India (2006), Okinawa, and Japan (2007 and 2014) suggest that it was introduced into Asia in the last decade. Though no economic or biological damage caused by this species has been reported in South Korea, the high density of M. squamiger (50–60 individuals/rope-meter) is a potential hazard to other native species via fouling and competition for food and space. Therefore, further research is needed to determine the possible vectors and to continue to monitor its possible spread.

Based on the morphological characters and the mitochondrial cytochrome oxidase subunit I (mtCOI) genes, 132 specimens of marine mussels from Guangdong Province and Hainan Province were identified as Mytella strigata (Hanley, 1843). This is the first report of this species in this region. Here, we investigated the worldwide dispersal and biogeographic patterns of M. strigata based on mtCOI haplotypes from both native and invaded regions. As a doubly uniparental inheritance species, the haplotype differentiation of female-lineage mtCOI (510 bp) and male-lineage mtCOI (433 bp) in M. strigata specimens was investigated. The result showed two haplogroups in both matrilinear and patrilinear haplotypes. Genetic relationships among haplotypes identified Colombia as the origin of M. strigata in Indo-West Pacific regions. We hypothesized the invasion of M. strigata to China, Singapore and Philippines happened at about the same time, around 2014 but diffused rapidly in recent years. We also proposed the ballast and biofouling were pathways of long-distance invasion for M. strigata, e.g., from South America to Indo-West Pacific regions, but the ocean and coastal currents promoted diffusion within small ranges. This study might provide useful information for the prevention and management of this invasive species.

Over the last decade, the calanoid copepod Pseudodiaptomus marinus — native to the Indian Ocean—has rapidly spread throughout the European Seas. Here we report its first occurrence in the southern Levantine Sea. Zooplankton samples were collected monthly by vertical net hauls in a coastal monitoring station at the Israeli Mediterranean Sea during 2019–2021. The samples were analyzed using mitochondrial COI and 18S rRNA metabarcoding, revealing the occurrence of P. marinus in winter and spring. Following the molecular detection, two individuals of P. marinus were observed in the samples and identified morphologically, indicating a low population abundance (0.4 ind. m^-3) and confirming its status as widespread but rare, as reported in former colonized areas. Rare species often go undetected in zooplankton assemblages using morphological examination, whereas DNA metabarcoding is a sensitive, rapid, and cost-effective method that can provide valuable presence/absence data of such species. We further show that the use of both mitochondrial and nuclear gene markers provides a robust and comprehensive non-indigenous species (NIS) early-detection system, and stress that combining DNA metabarcoding with morphological examination is necessary for biodiversity monitoring in marine ecosystems that undergo significant transformations due to climate and/or anthropogenic forcing.

Aquatic ecosystems are under threat from nonindigenous species invasion. Fouling organisms on ship hulls are constantly in transit, posing a threat to recipient communities by reducing biodiversity and causing severe economic and public health impact. In the south of Iraq, a range expansion for the nonindigenous barnacle Amphibalanus subalbidus was recorded. On a West Asian scale, Shatt Al-Arab could be a hotspot for biological invasions in Iraq, since this river connects the Persian Gulf to inland waterbodies. Amphibalanus subalbidus could establish settlements in a variety of habitats due to its highly oligohaline distribution, which can withstand prolonged exposure to fresh water. Thus, a morphological consideration and their related distribution in the south of Iraq are discussed for this invasive species.

The Papahānaumokuākea Marine National Monument (PMNM) is one of the world’s largest marine protected areas and covers marine habitats as well as the islands and atolls of the Northwestern Hawaiian Islands. Despite its protected status, the biodiversity of the PMNM face several threats to its preservation, including the presence of introduced species. Given its history as a shipping and military outpost, Midway Atoll represents a potential entry point for introduced species to the PMNM. Thus, monitoring for new introduced species in Midway is of importance for the management and preservation of the PMNM. In this study, we use morphological and molecular approaches to confirm the presence of the coastal isopod Ligia exotica, a species of Asian origin that has been introduced to coastlines around the world, in Midway Atoll and thus the PMNM. The presence of L. exotica in Midway Atoll is of concern as islands of this marine monument harbor endemic species of Ligia isopods.

A juvenile American lobster, Homarus americanus H. Milne Edwards, 1837, was recorded for the first time in European waters in August 2019, with the capture of a single early benthic phase specimen during surveys along the North East England coast. Identification was determined by a combination of morphological and molecular approaches. The record raises serious questions of whether the species is now breeding in the region, with associated implications for its invasiveness. The mechanisms of introduction, invasion status, risks to native shellfisheries, and directions of future study are discussed.

Non-native aquatic plants, as ecological engineers, change physical and chemical characteristics of invaded environments, and re-arrange the biological relationships within the colonized aquatic communities. Fanwort (Cabomba caroliniana) is a submerged aquatic plant native to the South America and southeastern United States. This species was introduced to China over 20 years ago and because of its quickly growth, large distribution and negative ecological impacts, it is included in the List of Invasive Alien Species in Chinese Natural Ecosystems by the Ministry of Ecology and Environment of China. Lack of detailed information about this species has limited its effective management and control. We summarize the introduction pathway of fanwort, its current distribution throughout China (including longitude and latitude), and the ecological impact on native species, waterways, agriculture and invasions by other non-native species. based on our investigations and a review of the literature. This study provides useful information for researchers and environmental managers to better control fanwort and other non-native aquatic plants in China.

Salvinia minima Baker (Salviniaceae) has been recorded for the first time in Africa. This South American native macrophyte is highly invasive and damaging, costing millions of dollars to control in the USA, and has the potential to invade many of southern Africa’s waterbodies. Field surveys have confirmed the presence of S. minima from four sites in South Africa, with the largest invasion occurring on the highly polluted Hartbeespoort Dam, north east of the country’s capital. Salvinia minima has been targeted for biological control in South Africa, using the weevil, Cyrtobagous salviniae, which is undergoing host specificity testing under quarantine conditions.

Alien aquatic plant species have significant ecological and economic impacts on freshwater ecosystems and are mentioned amongst the major threats to aquatic biodiversity. Detection of alien species at the beginning of invasion can help avoid their spread and prevent negative impacts on aquatic ecosystems. This study presents the first records of invasive species Elodea nuttallii in Lithuania. This species was found in three localities of the Nemunas River (southern Lithuania) in 2020 and 2021. The localities were mapped using system grid cells arranged based on geographical coordinates with sides of 6′ latitude and 10′ longitude. The habitat characteristic and associated species were presented. The identity of Elodea nuttallii was confirmed using a molecular method (sequencing of two regions ITS and psbE-petL). The molecular analysis was effective in supporting the identification of individuals collected in the early stages of growth. We suppose that Elodea nuttallii may be more widespread in the region of north-eastern Poland, north-eastern Belarus and southern Lithuania and will continue to spread north and northeast directions. The expansion of Elodea nuttallii can have a negative impact on valuable natural habitats, particularly on protected throughout Europe water courses with the Ranunculion vegetation.

Here, we report the first record of quagga mussel, Dreissena bugensis Andrusov, 1897, in Italy. This mollusc is native of the Dnieper River drainage of Ukraine and is one of the most aggressive invaders in freshwater ecosystems. The spread of quagga mussels throughout Europe and Northern America begun during the 1940s and 1989, respectively. Individuals of quagga mussel were identified in February and March 2022 in two stations located in the shallow (Bardolino) and deeper basins (Castelletto di Brenzone) of Lake Garda. Samples, collected with an Eckman grab, allowed identifying individuals of quagga mussel attached on macrophytes, stones and other mollusc shells. The identification of the individuals was carried out both through the analysis of morphological characters and genetic and phylogenetic analyses using the mitochondrial COI gene. The discovery of quagga mussel is the last of a long series of reports of non-indigenous species introduced into Lake Garda. Lacking direct connection by rivers or canals with other waterbodies colonized by D. bugensis at the northern side of the Alps, a more probable cause of introduction of this new species into Lake Garda can be due to unintentional overland transport through recreational boats and fishing gear. With this new discovery, Lake Garda has confirmed its pivotal role as a southern Alpine corridor for the introduction of non-indigenous species previously established at the northern border of the Alps. Considering its high colonization rate and compared with other invasion patterns observed in Europe and North America, it can be assumed that D. bugensis will soon establish itself with dominant populations throughout Lake Garda. At the same time, it can also be assumed that it will soon spread to other Italian water bodies.

To date, only two Cherax species have been reported to occur in Italy, i.e., C. destructor Clark, 1936 and C. quadricarinatus (von Martens, 1868), both in the wild and in aquaculture farms. Therefore, we aimed to update their current status and distribution in Italian mainland and Sicily. In addition, we investigated the origin of their known populations, and their possible routes of invasion. In order to genetically characterize the Cherax populations occurring in Italian inland waters and aquaculture facilities, the barcode region of the mtDNA gene cytochrome oxidase subunit I was sequenced in the available specimens originating from an aquaculture facility and a museum collection. The sampling campaigns conducted in 2021 did not lead to the collection of any Cherax individuals in the sites where the species was formerly reported to occur. The recent failures to detect Cherax spp. from Italian inland waters might be due to the inability of the species to cope with the Italian climate, which is likely for C. quadricarinatus but less so for C. destructor, to the possible impact of the alien red swamp crayfish Procambarus clarkii (as well as its indirect impact i.e., the spread of the crayfish plague for which yabby is susceptible), which occurs in both the sites where C. destructor was reported in Italy, or to the burrowing habits of the species, which might lead to overlook their presence when present at low densities. In the light of the well-known impact of invasive crayfish and considering the scant knowledge about the current distribution and status of Cherax species in Italy, a regular monitoring of their possible presence is recommended.

While monitoring the invasive freshwater invertebrates in Romania, specimens of a previously unknown prawn were reported on social media (Facebook) to occur in the lower reaches of the Danube and Pruth rivers. First individuals, including ovigerous females, were captured at Galați in a floodplain pond of the Danube in August 2021 and kept in an aquarium by a local hobbyist until their release back in the same place. In November 2021, several other specimens were observed and photographed in the lower Pruth at Slobozia Mare (Republic of Moldova). One adult male was captured by a crayfish catcher in November 2021 on the Chilia arm of the Danube Delta at Ceatalchioi. There were already several reports of numerous individuals captured by local crayfish trappers in the lakes Ligheanca, Băclăneștii Mari and Fortuna in the Romanian Danube Delta in July 2022. All these individuals were identified as the oriental river prawn Macrobrachium nipponense. The invasion history of M. nipponense in the area is inferred based on currently available literature and social media sources.

On March 25, 2022, one specimen of the Sohal surgeonfish Acanthurus sohal and one of the Violet-eyed swimming crab Carupa tenuipes were collected for the first time off the north coastline of Egypt and Libya, respectively. The native range of both species includes the Red Sea, and here, they are reported for the first time from the southern Mediterranean Sea. The second record of the Lessepsian migrant Pteragogus trispilus from Libyan waters, also caught on March 25, 2022, is furthermore included.

Invasive species form an important threat to autochthonous biodiversity and ecosystems, as they may negatively affect native species. Pentacoelum kazukolinda is an invasive maricolan flatworm with a freshwater ecology that was already known to be widely distributed in the Northern hemisphere: USA (Hawaii), Spain, Germany, The Netherlands, and Japan. Here we detail the first records from Chile, Peru, and continental USA. These new records from North and South America were substantiated by observations on the very characteristic external appearance of the specimens, their anatomy, and/or molecular data. We demonstrate for the first time that the animals are capable of regeneration. At the newly discovered localities in South America, this flatworm co-occurs with introduced snails, which may constitute its prey species, and with introduced aquatic plants that may have facilitated its introduction into the New World.

Invasive species are one of the main causes of biodiversity loss worldwide. As introduced, populations may increase in abundance and expand geographical range, so does the potential for negative impacts on native communities. As such, it is necessary to understand the processes driving range expansion, before a species becomes established in new areas. Through an investigation into capacity for population growth and range expansion of introduced populations of a non-native lizard, we aimed to demonstrate how multi-scale factors influence spatial spread, population growth, and invasion potential in introduced species. The Italian Wall Lizard (Podarcis siculus) was introduced multiple times to the United States with extant populations in California, Kansas, New Jersey, and New York. Recently, a single specimen was discovered in British Columbia, Canada, and unstudied populations are on Orcas Island and Missouri (USA). We used phylogenetic analysis of mtDNA sequences (cytb gene) of individuals sampled from these introduced populations and across the native range to identify potential source populations. Our phylogenetic analysis result with documentation of the introductions revealed that the Canadian individual is derived from the Tuscany clade (together with samples from Kansas and New York). The New Jersey population is likely from the Adriatic clade and the Californian one from Sicily. The Orcas Island and Missouri populations still require study. Consequently, humans are key drivers of the distribution of alien reptiles in North America, but the distributions are determined by a complex interplay between human activities, geographic factors and species features. Genetic evidence is essential for reliable biogeographic assessment of invasive species, particularly in systems with a long history of human influence.