To enrich spatio-temporal information on the distribution of alien, cryptogenic, and neonative species in the Mediterranean and the Black Sea, a collective effort by 173 marine scientists was made to provide unpublished records and make them open access to the scientific community. Through this effort, we collected and harmonized a dataset of 12,649 records. It includes 247 taxa, of which 217 are Animalia, 25 Plantae and 5 Chromista, from 23 countries surrounding the Mediterranean and the Black Sea. Chordata was the most abundant taxonomic group, followed by Arthropoda, Mollusca, and Annelida. In terms of species records, Siganus luridus, Siganus rivulatus, Saurida lessepsianus, Pterois miles, Upeneus moluccensis, Charybdis (Archias) longicollis, and Caulerpa cylindracea were the most numerous. The temporal distribution of the records ranges from 1973 to 2022, with 44% of the records in 2020–2021. Lethrinus borbonicus is reported for the first time in the Mediterranean Sea, while Pomatoschistus quagga, Caulerpa cylindracea, Grateloupia turuturu, and Misophria pallida are first records for the Black Sea; Kapraunia schneideri is recorded for the second time in the Mediterranean and for the first time in Israel; Prionospio depauperata and Pseudonereis anomala are reported for the first time from the Sea of Marmara. Many first country records are also included, namely: Amathia verticillata (Montenegro), Ampithoe valida (Italy), Antithamnion amphigeneum (Greece), Clavelina oblonga (Tunisia and Slovenia), Dendostrea cf. folium (Syria), Epinephelus fasciatus (Tunisia), Ganonema farinosum (Montenegro), Macrorhynchia philippina (Tunisia), Marenzelleria neglecta (Romania), Paratapes textilis (Tunisia), and Botrylloides diegensis (Tunisia).

The distribution range of the American comb jelly Mnemiopsis leidyi has expanded across Europe for several decades, particularly in the eastern Atlantic and Mediterranean Sea. This study aims to assess its expansion along the French Atlantic coast, mainly in the Bay of Biscay and Iroise Sea, since the first record in 2014. Mnemiopsis leidyi is now clearly established along 500 km of coastline, from the coast of Lorient to Arcachon Bay, which is the southernmost colonised area in the eastern Atlantic to date. It will likely colonise the Spanish Gulf coast in the near future through natural dispersal via currents, as has occurred between the Gironde estuary and Arcachon Bay. We quantify that this species now colonises nearly 45% of the French coastline. The invaded area includes the main estuaries of the Seine, Loire, Gironde and Rhône rivers, where M. leidyi populations may constitute reservoirs for colonising other harbours through merchant vessel traffic via ballast water. Finally, the Marennes-Oléron Bay and Arcachon Bay are the two main spat-producing regions for the Pacific oyster Magallana gigas in France. As M. leidyi consumes bivalve larvae, the potential economic and ecological impacts on this shellfish industry are discussed.

The brackish water mytilid mussel Mytella strigata (Hanley, 1843) is recorded for the first time in July 2022 in Hong Kong. Native to Central and South America, the first reports of M. strigata in Asia were recorded in the Philippines, with subsequent reports from India, Singapore, Thailand, and Taiwan. Here, the mussels were found attached to hard, artificial substrates throughout the Tolo and Victoria Harbours in Hong Kong, with 13 accessible specimens collected and more inaccessible specimens observed. Mytella strigata tended to co-occurr with a previously recognised introduced mussel, Xenostrobus securis (Lamarck, 1819). The largest individual observed had a shell length of ~ 54 mm and the smallest ~ 22 mm, and all specimens were found in brackish water areas. Externally, the shells were generally black with a green tinge and internal surfaces were iridescent purple. Two small teeth on the internal anteroventeral margin, typical of Mytella, were observed. With the recent introduction of M. strigata throughout Asia, future research is required to document the full extent of the population within Hong Kong, as well as developing a greater understanding of the ecological and economic impacts of this highly invasive species.

Perkinsus marinus belongs to the Chromista Kingdom and is recognized as an opportunistic parasite of mollusks native to the west coast of the Atlantic Ocean. The native range of this species is the Atlantic Ocean, however, it was introduced to the Gulf of California (GC) by a transfaunation of oysters. This microorganism has invaded new niches in the GC and continues to colonize different species of bivalve mollusks. For the first time, P. marinus was detected in the mussel Mytella strigata from the southeast coast of the GC in 2020 by staining and molecular techniques. The moderate number of cells of this myzozoan in the mussel coincides with the reports for other species of ostreids, venerids, and mytilids in the area, which suggests that it is expanding its geographical range and host species. The invasive potential of the parasite in new environmental niches and species of mollusks with commercial importance elevate the need for a risk assessment.

The American blue crab, Callinectes sapidus Rathbun, 1896 is native to the western Atlantic. The present work reviews the spread of C. sapidus in the European Atlantic, the Mediterranean, Black Sea and Sea of Azov, and identifies its first occurrence in the Merja Zerga and Khnifiss lagoons on the Moroccan Atlantic coast. These first and southernmost records on the African Atlantic widen the current biogeographic distribution of the species worldwide. Genetic analysis of specimens from both the Mediterranean (Marchica lagoon) and Atlantic (Merja Zerga and Khnifiss lagoons) coasts of Morocco, based on COI (Cytochrome c oxidase subunit I), confirmed the species sequences as being those of Callinectes sapidus. Moroccan populations have low haplotypic diversity with only two haplotypes (haplotype 1 and haplotype 7). These two haplotypes correspond to the two different haplotypes already found in the Mediterranean. Haplotype 1 from Merja Zerga, Marchica and Khnifiss lagoons was 100% identical to the sequences ON248058 in GenBank, while haplotype 7 from the Marchica and Merja Zerga lagoons was 100% identical to the sequences ON248059. Very likely, the origin and pathway of colonisation of the populations established in the three Moroccan lagoons is the result of the expansion of the species along the Mediterranean Sea and now the Atlantic coast of Africa.

Here we report the first record of the Marbeled spinefoot, Siganus rivulatus Forsskål and Niebuhr, 1775 (Acanthuriformes: Siganidae), collected in July 2022 from Maltese coastal waters. The specimen was identified through morphological characters and confirmed genetically through DNA barcoding, given that the family Siganidae is composed of several species belonging to only one genus with similar and overlapping morphological characters. Previous to this report, the closest record of S. rivulatus was off the island of Sicily. Thus, the presence of S. rivulatus in Maltese waters suggests that this species is expanding its distribution within the Mediterranean Sea. Additionally, this study compares this central Mediterranean record of S. rivulatus with genetic data of the Dusky spinefoot, Siganus luridus (Rüppell, 1829), a previously established species. Individual records of Siganus (rabbitfishes) are important to note, as they represent the first warning signs of a possible invasion. Previous work has shown that these species drastically alter the ecosystems of the Mediterranean region through their herbivorous diet and grazing behaviour. Therefore, we need to closely monitor for more individuals and establish mitigation measures against established and expanding populations of these two species.

Kellicottia bostoniensis is a natural planktonic species from North America. This has already been identified as alien/invasive in Europe, South America and Asia, having a relationship between the size of the rotifer and the trophic states, depths, and pH values of the water body. This work aims to describe a new occurrence of K. bostoniensis in a dam for recreational activities and urban water supply in southern Brazil. Sampling was carried out using oblique hauling, with a 68 µm cylindrical-conical net close to buildings in the water supply catchment area and the hydroelectric plant at the Alagados Reservoir. The occurrence of K. bostoniensis in this area of the dam described as having a lentic environment dominance, and subject to Cyanophyceae blooms raises the alert for the arrival of this rotifer in Campos Gerais. In addition to encouraging the need for studies on the impact of this species on native zooplankton and its potential to be an indicator species of aquatic environments.

Citizen scientists may provide unique opportunities for surveillance and early detection of management-relevant biological invasions. Here, we report results of a classroom citizen science program that detected the first record of the invasive red swamp crayfish Procambarus clarkii (Girard, 1852) from northern Idaho, United States. Secondary school students trapping storm water ponds in a public park of Lewiston, Idaho detected an unusual crayfish that they identified as P. clarkii. We confirmed this identification by crayfish morphology and mitochondrial DNA barcoding. Management agencies were promptly notified and have initiated monitoring and removal efforts for this population, which directly neighbors a major river in the study region. Procambarus clarkii may be well-suited to citizen science surveillance by classroom programs because of its tendency to invade freshwater ecosystems like storm water ponds in urban and suburban landscapes.

We report the first occurrence record of the spiny-cheek crayfish Faxonius limosus in two North-western Italian lakes: Orta and Mergozzo. We also confirm the occurrence of the species in Lake Maggiore. Faxonius limosus is native to the east coast of the USA. Since the end of the 19th century, it was introduced to Europe, where it rapidly spread in Poland, Russia, France, and Germany. In 1991, it was recorded for the first time in Italy in Lake Iseo (Lombardy region; NW Italy), and soon it has spread in Northern and Central Italy. Although Faxonius limosus is included in the list of European Union Concern, only two reports suggested the occurrence of this species in lakes Maggiore, Orta and Mergozzo, but these were never confirmed by experts. The aim of the present paper is to shed light on the distribution of F. limosus along the coasts of the three North-western Italian lakes. To this end, we used visual census and trapping to detect the occurrence of F. limosus, providing also georeferenced and environmental information of its habitat. We discovered 31 new occurrence localities (18 municipalities) for the species, scattered across the three lakes. These new findings highlight the urgency of implementing monitoring and management programs to prevent F. limosus spread and to mitigate its potential ecological impacts.

Crayfish are of major ecological importance within freshwater ecosystems, due to their central position in the trophic niche, acting as regulators of food webs. However, the introduction of exotic crayfish species threatens native species. Indeed, these introduced crayfish often outcompete local species and can even disseminate pathogens (i.e. exotic American species with the crayfish plague, Aphanomyces astaci Schikora, 1906), leading to rapid population losses. We report here the first record of rusty crayfish Faxonius rusticus in the wild in France and in Europe so far. The situation is alarming because F. rusticus is native to North America, potentially carrier of A. astaci, and classified among the most invasive species of crayfish in the world, due to its impressive dispersal capacities. This study reports high densities of individuals from a pond along the Inières Brook, where all size classes are represented, both adults and juveniles. A total of thirty-seven specimens were also observed over 2.5 km of the Inières brook as well as the Briane (main stream) in 2019 where this species co-occurs with another invasive crayfish species, the signal crayfish Pacifastacus leniusculus. In these sites, all specimens of both species were positive for crayfish plague presence with some individuals showing high level of infection (A5) (on an A0 to A7 scale), rarely observed in specimen of other invasive crayfish species. Since these first observations, the situation seems to have worsened, with 847 individuals captured, in the pond along the Inières brook, during survey sessions in 2021.

Non-native aquatic plants are important considerations in environmental management because of their rapid growth, ability to disperse and establish feral populations quickly, and because of their negative ecological and economic impacts. Yellow bur-head (Limnocharis flava) is an emergent aquatic plant native to tropical and subtropical America that has been introduced primarily through the aquarium trade on all continents except Antarctica. Recently, this species has developed naturalized populations because of its widespread use in constructed wetland restoration projects and aquatic gardens. There is little information about yellow bur-head in China and the lack of scientific research and monitoring has made the management of this non-native aquatic species challenging. In this study, we review introduction pathway, current distribution, and ecological impacts caused by yellow bur-head through field surveys and a review of the literature. Yellow bur-head introduced in China as ornamental plants and spread quickly due to aquarium trade, ecological restoration. Now, this species has successfully established feral populations in 11 Provinces of south China. And this species caused significant negative impacts on native biodiversity and grain production. Thus, more attention should pay on monitoring and management of this non-native species. This study provides useful information for researchers and managers of non-native aquatic plants in China and other regions.

Parrot-feather (Myriophyllum aquaticum) is an aquatic plant in the water milfoil family native to South America. It is widely distributed across North America, Europe, Asia, Australasia, and Africa as an invasive species. Outside of its native range, parrot-feather is regarded as a troublesome weed, due to its ability to grow quickly and clog or stagnate shallow waterways. We report six sightings of parrot-feather in the state of Massachusetts, USA from 2006 to 2017 compiled from state-organized surveys. Approaches to control this invasive species, such as physical removal, chemical treatment, and potential biological agents, are also discussed in this report, with specific recommendations made to expand monitoring efforts in Massachusetts and control newly detected populations.

Sisyrinchium is one of the largest genera in Iridaceae, comprising more than 200 species and native to Hawaiian Islands, Temperate and Subtropical America to Falkland Islands. In Bulgaria, the genus was first reported in 1972 with the species S. angustifolium. In 2020, during field work near the Oshtava village, Kresna district (SW Bulgaria), a species of Sisyrinchium was discovered. The taxon was identified as S. rosulatum. The aim of the present article is to report S. rosulatum as a new species to the Bulgarian flora and to provide data about its main distinguishing morphological characters and its distribution and habitats in Bulgaria. The genome size of the species, obtained from the Bulgarian accessions, is 1C = 1.00–1.08 pg which is congruent with earlier data from elsewhere. Based on field observations, it can be inferred that S. rosulatum is a naturalized, yet non-invasive alien species in the Bulgarian flora. A careful examination of the previously collected herbarium material of Sisyrinchium from Bulgaria revealed all specimens belong to S. rosulatum.

The so-called “Asian mystery snails” are a group of large freshwater snails that are regarded as invasive in many parts of the world, including the United States, where they have outcompeted native gastropods and have become the dominant molluscan fauna in many lakes and rivers. One notorious, species, the Japanese mystery snail, Heterogen japonica (Martens, 1861) was first detected from food markets in California in the late 1800s but since then has never been reported from the region, and instead only the Chinese mystery snail, Cipangopaludina chinensis (Gray, 1834) has been found. This has led to some confusion as to the identity of these mystery snails at what was supposedly the point source of introduction. Unfortunately, these early specimens have been lost and so their identity cannot be confirmed, even morphologically. In this study we used DNA barcoding for the first time to clarify the identity of the mystery snails in a section of the Sacramento River in California which has never been explored for these animals. Our results provide the first genetic confirmation of H. japonica from California more than a century after it was supposedly detected. Heterogen japonica has now been genetically confirmed from every corner of the United States. Its cosmopolitan distribution is reflective of not only its broad physiological tolerance but also the wide variety of vectors which may have aided in its dispersal.

Hawaii, despite being only about 0.2% of the land mass of the continental United States, accounts for nearly half of all endangered species listed under the Endangered Species Act. Among the most prominent threats to biodiversity, including climate change and habitat destruction, impacts from invasive species are among the most notable. Each year dozens of novel plant and animal species are introduced and establish in Hawaii, and it is likely that many more go undetected. Those that establish and spread negatively impact the nearly 10,000 endemic species that evolved in isolation over millions of years. This process of rapid extinction of native species and replacement with globally distributed generalists is homogenizing Hawaii’s unique fauna, causing the islands’ biota to resemble more and more that of any other warm rocks in the ocean. The loss of biodiversity extends beyond species loss, and with each extinction, we are losing the stories and connections we have with the land through our shared evolutionary history, connections on which the hope to preserve the distinctive culture and ways of living in Hawaii, and globally, depend. Here we report the case of two newly recorded invasive snail species, Otala lactea and Zachrysia provisoria, and emphasize the necessity of formalizing and broadening partnerships to help stem the tide of invasive species and help conserve the valuable natural and biocultural resources on which island life relies. Hawaii, like many oceanic islands, serves as a microcosm for processes impacting the entire world. The lessons learned, and practices applied here can help develop prevention and management policies and actions that can be scaled up to stem biodiversity loss globally.

Species introductions are a major issue for biodiversity conservation and human well-being worldwide, but their impact can be particularly severe in oceanic island ecosystems. Here, we report the occurrence of two alien species on Terceira island, Rivellia syngenesiae (Fabricius, 1781) (Diptera: Platystomatidae) and Sceliphron caementarium (Drury, 1773) (Hymenoptera: Sphecidae), being the first reports of these insect families to the Azores archipelago. We provide the diagnosis of each species, information on their distribution and ecology, and discuss their potential impact on native biodiversity. Furthermore, we anticipate the spread of these species through the Azores islands, benefiting from the high increase in commerce and tourism, and stress the need to set a program for the early detection of alien species in the archipelago.

This study assessed the effects of the Argentine ant (Linepithema humile), an invasive species, on the indigenous ant fauna in Busan, South Korea. Ant communities were sampled using pitfall traps placed along two transects in areas where L. humile was recently discovered (2019) in South Korea. Overall, we identified 14 ant species belonging to 12 genera and four subfamilies. We found that the species richness of the native ant community was significantly lower in areas invaded by L. humile, and most epigeic ants from the study area were not found co-existing with the Argentine ant. Five native epigeic species, namely Nylanderia flavipes, Pristomyrmex punctatus, Tetramorium tsushimae, Formica japonica, and Lasius japonicus, were strongly impacted by the invasion. In contrast, no effects were observed on two epigeic species (Camponotus vitiosus and Monomorium chinense) and one hypogeic species (Brachyponera chinensis). These results indicate that the successful settlement of Argentine ant has had a significant negative impact on native ant diversity in South Korea, confirming that L. humile is a very effective and competitive colonizer, despite its restricted dispersal capability. Management programs need to urgently implement control measures to ensure that L. humile does not spread further in South Korea.

In this study, we present the first record of the alien Common Crevice-cricket Gryllomorpha dalmatina in Slovakia, which was found near Bratislava, the capital of Slovakia, in the village of Ivanka pri Dunaji. The Common Crevice-cricket was observed for the first time on the wall of an old building. During the two years of the study, our observations suggest a viable population successfully surviving in a human-made environment. The most important pathway of introduction seems to be transport of the species with horticultural material or stored products from the Mediterranean to Central Europe, indicating introduction as a stowaway. Our findings represent the tenth known record of a non-native orthopteran species in Slovakia and probably the sixth known occurrence of this alien cricket confirmed in Central Europe.

The Chinese banyan, Ficus microcarpa is an ornamental fig tree, widely planted throughout Southern Greece. Native to Asian – Australasian regions, it can be found in plazas, parks, roadsides as well as private gardens. Along with its host, various insect species have managed to follow and establish themselves outside of their native range. In Rhodes, the mass defoliation of an emblematic fig tree, led to the subsequent finding of Josephiella microcarpae infestation. Repetitive samplings in the following years confirmed the establishment of the species on the island, which constitutes the first record of this species in Greece. Collected specimens from Rhodes and Cyprus were sequenced for the COI DNA barcoding region. Further investigation of fig trees throughout various locations in Southern Greece, proved fruitless. Based on our findings, the distribution of J. microcarpae in Greece seems restricted in the city of Rhodes.

The Chinese banyan (Ficus microcarpa) is an Australasian fig tree commonly planted in urban and semi-urban sites throughout the warmer parts of the world. Assisted by its host-specific mutualist pollinator Eupristina verticillata (Agaonidae), F. microcarpa often manages to colonise urban areas outside its native range and can invade natural habitats. In Cyprus, the species is widely planted in city centres, town squares and parks, where seedlings have been observed. Increasing numbers of fig wasp species of Asian origin are being recorded from the Mediterranean and it appears that the pace of colonisation of F. microcarpa is increasing. Fig surveys in Cyprus during the last seven years have uncovered a total of 11 fig wasp species associated with F. microcarpa. The composition of the fig wasp fauna is described here. It includes two species previously unknown from the Western Palearctic: Sycophila petiolata Chen (Eurytomidae) and an undescribed species of uncertain generic affinity (Pteromalidae, Epichrysomallinae) that we refer to as “Eufroggattisca sp. indesc.”. The distribution, ecology and relationships of the Cypriot fig wasps associated with the Chinese banyan are discussed, together with their potential impacts on the spread of their host plant.

In July 2021, based on a series of photographs posted in the citizen science platform iNaturalist, the Chief Plant Health Officer Unit of Victoria was alerted to a sighting of a suspect exotic chrysomelid from the Royal Botanic Gardens (RBG), East Melbourne, Victoria, Australia. Specimens were collected and forwarded to the Crop Health Services diagnostic laboratory (Agriculture Victoria) for identification. These were identified as Megabruchidius tonkineus (Pic, 1904) (Chrysomelidae: Bruchinae) based on literature, reference specimens and via COI barcoding. This report presents the first record of M. tonkineus, which also represents the first record for the exotic genus Megabruchidius Borowiec, 1984 for Australia.

The Palearctic ground beetle Carabus granulatus Linneaus, 1758 has been accidentally introduced to North America on multiple occasions. We review previous reports of its North American colonization history, and document range expansion into northern California, Montana, New York state, Vermont, and Maine. We also review its several reported interceptions. The species is eurytopic, occupying marginal heathland and open wet forest habitats in the Old World, and is not particularly associated with human habitation. New World populations retain these habitat preferences, with established introductions often occurring along coastlines or waterways. Spread by the flightless C. granulatus in North America is compared to two other carabid species introduced to North America: 1, the exceedingly synanthropic, also flightless, Carabus nemoralis Müller; and 2, the flight-capable, extremely eurytopic Nebria brevicollis (F.). Geographic expansion in all three species is positively associated with breadth of habitat preference, dispersal ability, and degree of synanthropic association. For all three species, transport via human activities is an important factor promoting range expansion. Based on the Palearctic distribution of C. granulatus, its North American range can be expected to expand trans-continentally, coalescing populations originating from the independent colonizations, while also expanding southward where habitats meet the ecological criteria necessary for the species’ persistence.

Monoxia obesula, a species native to the U.S.A. and adventive in western Mediterranean, is recorded in Greece for the first time. In 2022, one female specimen was collected on Théra Island (Santorini Archipelago, Aegean Sea), becoming the easternmost Mediterranean record. Host plants are Amaranthaceae species, particularly Atriplex halimus occurring in saline habitats. The presence of Monoxia obesula in Greece is alarming because it spreads its occurrence towards the eastern Mediterranean and may therefore pose a significant danger for Atriplex halimus stands.

Ambrosia artemiisifolia is North American plant species established and invasive in Europe. In 2013 its natural enemy, chrysomelid beetle Ophraella communa was first recorded in Italy and Switzerland. Since then, it has been spreading spontaneously and unintentionally with transport across Europe. Until now, it has been recorded only in the southwestern part of Slovenia in 2017 and around Ljubljana in 2019. Here we report the first records of O. communa in the north–eastern part of Slovenia. Thirty-four sites with A. artemisiifolia stands were inspected for the presence of any developmental stage of O. communa. Adult beetles and all other developmental stages were registered at two distinct locations near the cities of Celje and Maribor in 2022. One case of predation of Zicrona caerulea on O. communa larva was also observed.

Several non-native fish species were recorded in the studies of Eurasian otter Lutra lutra diet in south European and English rivers. To document the role of alien species as a prey of this aquatic top predator in central Europe, the diet of the otter was studied by spraint analysis in the Vistula, a large European river. Fresh spraints were collected at the study site in central Poland from 2012 to 2016, and in south Poland in 2015. At both sites, fish were the staple food of otters, constituting over 90% of prey consumed. The food niche breadth of otters was relatively high. Among 20 fish species registered in the diet, there were four alien species: prussian carp Carassius gibelio, common carp Cyprinus carpio, topmouth gudgeon Pseudorasbora parva, and round goby Neogobius melanostomus. Besides alien fish species, the invasive spiny cheek crayfish Orconectes limosus was present in the diet of otters at both localities. Altogether, the five invasive species constituted a large proportion of the diet of otters at both sites (over 30%). According to the literature data and results of this study, at least 18 non-native fish species were preyed on by otters in Europe. It is suggested that alien prey will constitute an increasing fraction of the diet of the indigenous Eurasian otter..