The occurrence of Brugmansia suaveolens (Solanaceae), a neophyte native to South America but cultivated for traditional medicine and ornament in many tropical and temperate areas of the world, is reported for the first time as casual for continental Europe. The species was discovered in two small populations in southern Italy, along the Tyrrhenian coast of the Campania region. Notes of the environments in which the species was found and its naturalization status are also presented. This new finding confirms the role of anthropic areas as starting points for the invasion processes in Italy.

Besides the well-known negative effects of invasive plant species on autochthonous plant communities, the breakdown of genetic integrity of indigenous species via alien-to-native hybridisation represents an additional direct threat to native flora which should not be underestimated. Our aim was to survey the current distribution of Solidago ×niederederi, a hybrid that has originated through spontaneous hybridisation between the native European S. virgaurea and allochthonous (North American) S. canadensis. Although this hybrid was first recorded at the very end of the 19th century, most occurrences have been reported during the last decades. It is only known to grow in Europe and its current distribution is still not well explored. Based on field research in the Carpathians, we list five new localities of S. ×niederederi, which represent the first records of this hybrid in Slovakia, Hungary, and Romania. The present paper documents existing reports from 409 sites in 17 European countries. We provide a detailed list of all records from the literature, freely available databases and webpages as well as a summary map of S. ×niederederi’s known distribution. In addition, records are analysed regarding a time context and habitat preferences. Finally, we discuss a potential threat that the hybrid could pose to the genetic integrity of the native European populations of the Solidago virgaurea complex.

Based on morphological characteristics, genome size and molecular phylogenetics the identity of introduced taxa of Artemisia section Artemisia in Belgium and the Netherlands was critically re-assessed. It was shown that several populations of alleged A. verlotiorum belong to A. princeps instead. This species is native to Eastern Asia (China, Japan and Korea) and has not been reported before from Europe. Since the time of its arrival in Belgium and the Netherlands, more than two decades ago, A. princeps was able to locally grow as massive stands in mainly non-natural habitats. Morphologically, A. princeps is in many respects intermediate between the native species A. vulgaris and the Chinese species A. verlotiorum. Morphology, genome size and phylogenetic analyses of these three species and A. ×wurzellii—which is a hybrid of A. vulgaris × verlotiorum parentage that spontaneously arose in the British Isles—are thoroughly discussed. Contrary to A. verlotiorum, A. princeps produces viable seed in Western Europe. Hence, it is able to reproduce both clonally and sexually and potentially is a much bigger threat to native biodiversity than A. verlotiorum.

Evolvulus nummularius (L.) L., a member of the Convolvulaceae, is native to Mexico and South America but nowadays grows around the world in many tropical and subtropical regions. Its presence in Pakistan, where it has become naturalized, is reported here for the first time. It was first discovered in Pakistan in the Jhok Reserve Forest in Lahore city of Punjab Province on September 5, 2016. It has since been found in four more localities in Lahore. Although E. nummularius has some medicinal value and is edible, it is usually considered a weed in the south and southeast of Asia. A detailed morphological description and comparison with other species is provided together with illustrations and an identification key for the two species of Evolvulus now established in Pakistan. In addition, the geographic distribution, ecology, economic importance, and invasive potential of E. nummularius are discussed. The description and key have been integrated with other floristic resources for Pakistan via two web sites, OpenHerbarium and KeyBase, to facilitate their discovery. Eradication of this introduced herb is probably impossible, but steps can and should be taken now to restrict its further spread within Pakistan before it affects the productivity of croplands.

A new record of Rubus (Rosaceae) for Ecuador is described: R. rosifolius, a climbing shrub introduced and naturalized in the Ecuadorian Andes for its edible fruits. We provide an updated key for the genus Rubus in Ecuador, a detailed description of the species, and its distribution. In addition, photographs of this species and complete illustrations are included.

Contemporary climate change, in particular higher temperatures, may greatly enhance the expansion of invasive species. Acacia longifolia (Fabaceae, subgenus Phyllodineae) is a native species of Southeast Australia and Tasmania, invasive in South Africa, Mediterranean Europe and South America. According to several records, this species has been introduced in Southern Brazil and Uruguay for fixation of dunes and for ornamental purposes in the mid-20^th century and has since then caused several environmental and socio-economic problems. However, its current distribution in these south American countries is undocumented, as well as the types of habitats it has invaded since its introduction. In this context, during May 2019 we performed a study through a latitudinal and climatic gradient along the coast, from southern Brazil (Santa Catarina and Rio Grande do Sul states) to Uruguay, to evaluate the presence of A. longifolia taking into consideration previous records of this species. Our observations showed an increase in tree density along the coast, from Brazil to Uruguay, with a clear distribution southward. It was not possible to confirm earlier observations of this species in southern Brazil (with the exception of Florianópolis), which may be associated with changes in temperature and precipitation in this region.

Bradybaena similaris (Férussac, 1822) is an invasive land snail species native to East and Southeast Asia. Here we report the first record of B. similaris in Bangladesh, an introduced species in this country.

The zooxanthellate, scleractinian coral Oculina patagonica is known from various locations in both west and east basins of the Mediterranean Sea, but there are only three casual records of this cryptogenic species from the Central-Ionian area, all from Malta in 2017. Surveys at 28 sites around the Maltese coasts undertaken during the present work revealed 43 colonies spread across ten sites. The coral occurred primarily on artificial substrata in harbour areas at depths shallower than 6 m, but a few colonies occurred on natural rocky bottoms and in non-harbour sites. The largest colonies reached a mean diameter of up to 95 cm and occurred on artificial structures that are only a few decades old, while the majority of the colonies were much smaller (< 40 cm diameter). This, together with the clustering of records in harbour areas, suggests that O. patagonica was likely introduced in Maltese waters in recent decades via maritime transport. The present results also confirm that this species is established in the Central Mediterranean area.

Specimens of the North-West Pacific Ocean isopod Ianiropsis serricaudis Gurjanova, 1936 were collected for the first time in 2019 from a harbour situated on the Normandy coast in northern France: Le Havre (192 specimens). I. serricaudis was recorded for the first time in Europe in the Netherlands in 2000 and for the first time in France (Arcachon) in 2013, the latter occurrence being due to oyster transfers. Although this species is non-indigenous to Normandy waters, it may have been introduced to France by oyster culture or by the fouling of the hulls of ships navigating between European countries and France.

Two Pacific amphipod species, Aoroides longimerus (94 individuals) and A. semicurvatus (three individuals), were recorded for the first time in 2019 in the English Channel. Aoroides longimerus was found in four sites along the Normandy coast (Granville, Cherbourg, Saint-Vaast-La-Hougue, and Le Havre) while A. semicurvatus was found only in two sites (Granville and Saint-Vaast-La-Hougue). Because both species were recorded (2009–2014) from the French Atlantic coast, they have probably been introduced to the English Channel through the accumulated fouling of the hulls of ships used primarily for recreational purposes or by transfer of the Japanese oyster Crassostrea gigas between oyster farms along the French oyster production intertidal zones.

Non-indigenous species are a recognized worldwide threat to biodiversity, to the economy and even to human health. Hence, analysis of principal descriptors of their occurrence is pivotal to set reliable conservation strategies and appropriate management. In this paper, we have reported the first record in the Marchica lagoon (Southern Alboran Sea) of the invasive Caprella scaura Templeton, 1836, an amphipod species likely native to the Indian Ocean and now recorded worldwide. Caprella scaura is widely distributed in the lagoon, and its abundance fluctuated between 3 and 337 ind./m². The species is well established in the Marchica lagoon and spreads over various ranges of depth (0.4 to 7.7 m), water temperature (14.21–28.97 °C), salinity (32.28–38.04) and substrates (bare and vegetated). This clearly confirms its large plasticity and highly invasive behaviour. The species has been introduced to the Marchica lagoon most likely via shipping activity. The recent settlement of three well established invasive species in the Marchica lagoon (Bursatella leachii Blainville, 1817, Callinectes sapidus Rathbun, 1896 and Caprella scaura) reveals that this coastal ecosystem is at risk of biological invasions and has to be monitored regularly in order to evaluate potential ecological impacts on the ecosystem.

Zebra mussels Dreissena polymorpha were first discovered at very low densities in Lake Mille Lacs, Minnesota in 2005. This provided a unique opportunity to document the rate of growth of a zebra mussel population and examine impacts on water chemistry and other biota. Adult densities determined through dive surveys were fitted to a logistic growth model. From 2006 to 2012, average adult density increased from 0.0015/m² to 13,651/m², and demonstrated an exponential growth rate with 30-fold annual increase for the first few years before density dependence slowed growth. Population growth rate and maximum density were higher in sites with hard substrates than in sites that included significant amounts of sand. Veliger densities increased with adult density early in the invasion, but did not correlate well after adult density exceeded 150/m². Water clarity did not improve as mussel density increased, nor were changes observed in chlorophyll-a, total phosphorus, or total dissolved solids. Conductivity and total alkalinity both decreased significantly after adult densities reached 10,000/m². Direct colonization by zebra mussels greatly reduced the abundance of native unionids as well as introduced Chinese mystery snails Cipangopaludina chinensis, while other gastropod species showed little colonization by zebra mussels. Continued monitoring of this invasive population will provide a unique long-term look at zebra mussel impacts in central North America outside of the Great Lakes.

The signal crayfish (Pacifastacus leniusculus) is considered to be the most successful crayfish invader in Europe. It is present across the continental part of Croatia, with first records from the Mura-Drava river basin in 2008 and from the karstic Korana River in 2011. In both rivers, P. leniusculus presents an imminent threat to indigenous crayfish species (ICS). The aim of the study was to explore the range expansion of P. leniusculus 10 years after its first record in Croatia. Based on the data collected via an extensive literature search and our own fieldwork performed in 2018, we here demonstrated that P. leniusculus is the most successful non-indigenous crayfish species (NICS) in Croatia, with the invasion range covering the largest extent of Croatia compared to other NICS. Its dispersal rates in the rivers of the continental part of Croatia have remained among the highest in Europe. In the Drava River, recorded dispersal rate (21.3 km/yr) corresponded to the predictions made by the earlier study that estimated P. leniusculus dispersal over 10 years. However, due to the low number of caught individuals along the 128 km of the Drava River course, dispersal rates as well as invasion pathways (natural vs. human-mediated) need to be further explored. The predicted encounter of P. leniusculus with the invasive Faxonius limosus was not observed. In the Korana River, we observed a continued expansion of P. leniusculus invasion range in both upstream and downstream direction. Dispersal rates were higher in the upstream direction, potentially due to differences in competitive pressure by the native crayfish, Pontastacus leptodactylus, which abundances were 6 times higher at the downstream invasion front. In both rivers, a displacement of the native P. leptodactylus has been observed. Even though P. leptodactylus has been considered to be the most robust ICS, that successfully expands its range in water bodies of Croatia and Europe, it is also the species the most adversely affected by the range expansion of the P. leniusculus in the continental part of Croatia. Thus, the status of P. leptodactylus in Croatia should be monitored and re-examined.

Two individuals of the Smallscale codlet Bregmaceros nectabanus were collected on December 19, 2019 by bottom trawl off Mola di Bari (Italy, Adriatic Sea) at 100 m depth on a muddy bottom. This finding represents the first record of the Smallscale codlet from the Adriatic Sea. Up to now, records of this Lessepsian migrant species have been reported from the Central and Eastern Mediterranean Sea. The present record extends its known distribution northward.

On April 17, 2018, four specimens of the lessepsian barracuda Sphyraena chrysotaenia were captured in the Gulf of Heraklion in Crete. The specimens were genetically identified and their full morphological description is provided. The close morphological similarities of the lessepsian barracudas, as well as multiple nomenclature changes through the years have resulted in an extended confusion regarding their accurate identification and taxonomy. The detailed morphological descriptions provided in this work coupled with DNA barcoding of the specimens, intends to provide verified data that will hopefully aid future specialized research aiming to alleviate this problem. To date, this is the first genetically confirmed record of this particular barracuda in Crete.

The second record of the Queen angelfish, Holacanthus ciliaris (Linnaeus, 1758), is hereby documented for the Mediterranean, through a single individual spearfished within Maltese coastal waters. Considerations on the potential introduction pathway for the species, which is popular in the aquarium trade, are made.

The introduction of a non‐native fish species into an aquatic ecosystem presents significant ecological risks if the species is able to successfully integrate into the ecosystem. Lake Bosomtwe in Ghana is an impact crater lake which contains an endemic and a near-endemic cichlid species. Following the establishment of an intensive Nile tilapia (Oreochromis niloticus) cage aquaculture facility on the Lake in 2012 and it closure in 2015, there have been several unconfirmed reports of the capture of O. niloticus from Lake Bosomtwe by local fishermen. On 6^th February 2020, the first documented observations of O. niloticus in the natural environment of Lake Bosomtwe were made using seine net catches. Nine more seining activities were carried out between 6^th February and 17^th April, 2020, and the presence of the O. niloticus was confirmed during all sampling events. Oreochromis niloticus constituted between 2 and 10% of the captured cichlid species composition. The introduction of the species warrants larger-scale comprehensive studies on the possible detrimental interactions with native species, and on changes to ecosystem function.

On October 4th, 2019, an angler caught and released a single northern snakehead (Channa argus) in a private pond in Gwinnett County, Georgia, USA. Pictures of the specimen were reported to the Georgia Department of Natural Resources, Wildlife Resources Division, Fisheries Management Section (DNR), and subsequent investigations by the DNR including electrofishing and rotenone surveys resulted in the capture and removal of 34 individuals from the area. Genetic analyses of fin clips from 33 specimens indicated the population consisted of a combination of juveniles from a breeding pair of captured adults and other unsampled adults. This discovery constitutes the first record of this non-native species in Georgia, and the results demonstrate how genetic analyses can facilitate effective understanding of invasion dynamics during rapid response operations.

There is scarce documentation of the presence of trout in the Puna and southern Altiplano in Chile, in spite of the risk that they represent for these ecosystems of high environmental value, which have endemic and highly threatened fish and amphibians. We report that Oncorhynchus mykiss has expanded its range to the entire Chilean Altiplano and that Salmo trutta occurs only in the extreme south of the Chilean Puna. The existence of trout culture stations is related to the presence of feral trout, which cohabit with threatened native fish and amphibians. The control of trout expansion, by protecting areas of high value for native fish and banning any future aquaculture projects in this area, are priority to avoid the invasion this species to new localities in these ecosystems. The presence of salmonids in the countries that border Chile make this a regional threat for the highlands of southern South America.

We report the first casual record of Eurasian wild boar Sus scrofa in Nahuelbuta Mountain Area, located in the coastal Temperate Forest of south-central Chile. Camera-trapping was conducted between January 2018 and February 2019 at two sites comprised by native native forest and commercial tree plantations. Wild boars were detected within plantations of Monterey pine mainly during Austral summer (December to February), daytime (between 11:00 and 20:00) and close (3 km) to Nahuelbuta National Park. The combination of its highly adaptable generalist behaviour and the extensive presence of commercial tree plantations in Nahuelbuta Mountain Area may favour the expansion of the invasive wild boar throughout this imperilled ecosystem, including its potential occurrence within the small and isolated protected areas present in it.

Shipping is the greatest pathway of non-indigenous species (NIS) introductions, and port areas are considered as alien hotspots. In this study, we analyzed data covering a 112-year period and found that Saronikos Gulf in Greece, hosting one of the largest container port terminals in Europe, is a hotspot of NIS introductions. To date, 89 NIS have been recorded, of which 8 are characterized as invasive. Most species belong to the taxonomic group of Mollusca (33%), followed by Pisces (22%). For the first time in the Mediterranean Sea, we report the presence of the micromolluscs Sinezona plicata (Hedley, 1899) and Ringicula sp. Moreover, we provide evidence for the trend of NIS introduction in the Saronikos Gulf across the past 70 years, the pathways of introduction and their importance through time, as well as the distribution of the most invasive species in the Saronikos Gulf. The information provided herein can assist the implementation of the EU Marine Strategy Framework Directive and inform NIS management. As Transport-Stowaway remains the main pathway of NIS introduction in the Saronikos Gulf, our principal recommendation is to reinforce regulations for the adoption of better antifouling practices and more effective ballast water treatment and management.