Scaevola taccada (Gaertn.) Roxb. is native of Asia and eastern Africa but has been introduced into the Americas as an ornamental urban plant. This paper reports, for the first time, the presence of Scaevola taccada in natural environments from southeastern Mexico. Several populations of S. taccada were identified during a botanical survey of the coastal dunes of the Cozumel Island Biosphere Reserve (State of Quintana Roo, Mexico) aimed at recording the most common plant species. Scaevola taccada is considered as an invasive species of coastal areas in this region. Evidence of its invasiveness is suggested by the fact that populations consisting of individuals of different size classes are found distributed throughout the island. Furthermore, they appear to belong to different generations since we found individuals of different sizes and with and without flowers and fruits. Our observations suggest that the population of Scaevola taccada can be in a process of expansion. Further studies are necessary to understand the potential effect on the native flora.

The seed beetle Megabruchidius dorsalis is an alien species first found in Europe in 1989 in Italy. Since then, it has been recorded in many European countries, developing inside the seeds of the ornamental trees Gleditsia triacanthos and Gymnocladus dioicus. Mature G. triacanthos pods were collected from the ground in Zagreb, Croatia in February 2020. Four adult specimens of M. dorsalis emerged from the collected material by the end of May 2020, which confirms the first record of this species in Croatia. We also provide a temporal distribution map of M. dorsalis and another species, M. tonkineus, in Europe.

In 2019, a survey of hard clam-cultured ponds along the southwestern coast of Taiwan revealed an unknown, almost ubiquitous, brackish water mussel. The mussels were attached to the concrete walls and drainage systems of the clam ponds, hulls of boats, bottom sediment, and riverbanks of the estuary. The largest individual had a shell length of over 6 cm. The general external color of the shells was uniformly dark brown or black, but shells with a dark greenish color were also found. The mitochondrial DNA cytochrome c oxidase gene sequences obtained from specimens were consistent with Mytella strigata from Singapore, India, and the Philippines. Based on interviews with farmers, the occurrence of this species has become common since 2014 and is increasing in abundance and density, suggesting that its first invasion may have occurred before 2014. The introduction vector of M. strigata may be ballast water discharged from ships or bio-fouled ship hulls from its native range or somewhere else in Asia. This report represents the first time this invasive tropical mussel (M. strigata) has been recorded in Taiwan and the fifth time it has been reported from the Indo-Pacific region. The rapid growth, high fecundity, and broad salinity tolerance of this species makes it a competitive threat to clams in the ponds as well as other native species.

In 2020, four populations of the marbled crayfish Procambarus virginalis, which is included on the list of Invasive Alien Species of Union concern, were discovered in northern Belgium. These records represent the first established populations of this invasive parthenogenetic species in the Benelux. The marbled crayfish seems well-established at all sites where it was discovered. Genetic analysis confirmed the species’ identity with the obtained COI Folmer fragments being 100 percent identical to reference sequences of P. virginalis from Germany, Italy, Sweden and the Czech Republic. We proposed a single diagnostic nucleotide for unambiguous character-based species identification between P. virginalis and P. fallax. The finding of this new species through opportunistic surveys instigated by citizen science reports indicates considerable knowledge gaps on crayfish distribution in Belgium. Considering the regulated status of most species in Belgium, we advocated the further set-up of dedicated crayfish surveillance using passive and active monitoring including environmental DNA detection.

Six individuals of Australian redclaw crayfish Cherax quadricarinatus (von Martens, 1868) (Decapoda: Parastacidae), the identity of which was confirmed through morphological and molecular characterization. They were caught from the wild environment in Terengganu, East Coast of Peninsular Malaysia. Since there is no record of redclaw aquaculture in close vicinity of the sampling site, it is hypothesized that the introduction of the species has been caused through a release by aquarists. Further studies are essential to understand the distribution and potential impacts of this invasive species in the area, and in the East Coast of Peninsular Malaysia.

Here we report the introduction and first observed breeding of the Arabian Serin Crithagra rothschildi in the eastern Arabian Peninsula. Although this species is the most widely distributed endemic bird in the western highlands of the Arabian Peninsula, this record represents a range expansion of approximately 1200 km beyond its established native range. Breeding was recorded twice, once in 2019 and once 2020, for two different pairs of birds. Early reporting of alien incursions is important, as combating biological invasions is most successful at the introduction stage. These records highlight the role of pet trade as a vector of alien species introductions. They also shed light on the impact that hunting, for the purpose of pet trade, exerts on birds in the western region of the Arabian Peninsula. We suggest that pet market monitoring may help to identify caged birds and prevent new introductions.

A marine bioinvasions Rapid Assessment Survey in August 2019, focused on marina floating pontoons in Rhode Island, Connecticut and New York recorded 21 non-indigenous, 22 cryptogenic and 2 range-expanding species. Five non-indigenous species (NIS) were found at more than 70% of the 10 sampled sites: three ascidians, Botryllus schlosseri (Pallas, 1766) (a probable mixture of introduced and native populations), Botrylloides violaceus Oka, 1927, and Styela clava Herdman, 1881; a crab, Hemigrapsus sanguineus (de Haan, 1835), and a sea anemone, Diadumene lineata (Verrill, 1869). The sea anemone Aiptasiogeton eruptaurantia (Field, 1949), native to the southern United States, is newly reported from New York. The southern U.S. barnacle Amphibalanus subalbidus (Henry, 1973) was detected for the first time in Connecticut in Long Island Sound. It had been six years since the last rapid assessment survey of marinas in Rhode Island and 16 years for marinas in Connecticut and New York. During this six to 16 year hiatus, we found northern range expansions, expansion of recent invaders and generally consistent presence of previous NIS at high levels of occurrence.

Invasive freshwater crayfish are spreading rapidly across the world. Here, we report the first record of Australian redclaw crayfish, Cherax quadricarinatus (von Martens, 1868) in Hong Kong, China. Identification of the captured crayfish was confirmed using external morphological features and molecular analyses. A total of 49 crayfish were captured from a stream pool and a reservoir in Pok Fu Lam Country Park using dip nets and funnel traps. The captured C. quadricarinatus ranged from 17.20 mm to 56.40 mm (mean = 30.70 mm) in carapace length and the sex ratio was 1:1. Since this species is globally recognized as an invasive species, a comprehensive survey on its status and invasion front, an investigation into its potential ecological impacts, as well as the formulation of a monitoring and removal strategy, are warranted.

The Chinese sleeper, Perccottus glenii, is an invasive species that has spread into Eastern Europe from its natural geographic range in Far Eastern Asia. Here, we provide a complex hydrobiological study of a marsh waterbody in the Ilgas Nature Reserve Natura 2000 site (Latvia) where we registered a monospecific fish community comprised of Chinese sleeper. While benthic organisms were predominant in the diet of Chinese sleeper of < 70 mm, the diet of larger fish (particularly around 90 mm) included an increasing proportion of juvenile Chinese sleeper (cannibalism). In the case of the Ilgas marsh, we believe that medium natural production (mesotrophic waterbody), piscivory and high competition for food has resulted in a monospecific fish community represented by Chinese sleeper alone.

We present the second edition of the checklist of alien and cryptogenic bryophytes (Bryophyta) in Austria. In total, four alien bryophyte species are reported, of which three are established, and for one it is unknown if it is casual or established. In addition, four cryptogenic species (i.e. species that are likely alien, but their biogeographic status is uncertain) are included, of which one is casual and one is extinct. In comparison with the first checklist of alien bryophyte species for Austria published in 2002, the number of alien or cryptogenic bryophytes has risen by four species. Most alien or cryptogenic bryophytes in Austria are native to continents of the Southern Hemisphere. Most invaded ecosytems in Austria are man-made habitats, fields, forests and mires. One species (Campylopus introflexus) is assumed to locally cause negative environmental impacts.

Urocaridella pulchella Yokeş & Galil, 2006 is a palaemonid cleaner-shrimp of Indo-Pacific origin that was first described from the Mediterranean Sea in 2006. However, limited information is available about its distribution and ecology due to the small size and cryptic habit of the species. We hereby report the first records of U. pulchella in marine caves and crevices of Greece, updating the species distribution that now spreads from the Levantine Sea to the South Aegean. Species identification was based on morphological examination and DNA barcoding of collected samples and in situ photographs. We also report on the fish cleaning behaviour of the species (based on observations of cleaning behaviour to the native Mediterranean moray eel, Muraena helena), the finding of an ovigerous-female and a wide distribution range, attesting to the establishment of the species in the area.

The Argentine ant Linepithema humile Mayr, native to South America, has been unintentionally introduced worldwide. Although L. humile usually forms an extremely large supercolony all sharing the same haplotype among members in its introduced ranges, four haplotypes (LH1, LH2, LH3, LH4) with different genetic structures have been discovered in Kobe Port (Port-Island and Maya Wharf), Japan. In 2019, a new L. humile population was discovered, the first since the initial invasion in 2006. Therefore, we identified the haplotypes among these newly invaded L. humile populations via mtDNA analysis and then compared the distributions among the haplotypes during these two time periods (2006 versus 2019). The haplotypes of all newly introduced L. humile populations corresponded to only the haplotypes previously detected in Kobe Port. Although the distribution ranges of haplotypes LH1 and LH4 changed little in Maya Wharf over approximately 15 years, major distribution expansions of LH2 and LH3 were found on Port-Island. Given the low natural dispersion ability of L. humile, it is likely that the range expansions of LH2 and LH3 on Port-Island were caused by the extensive transportation of construction materials within Kobe Port. In addition to strengthening the quarantine at existing trading ports, greater attention should be paid to the introduction of biological invaders in conjunction with the transportation of construction materials when new ports are developed and maintained.

Here, we report on the finding of an Asian invasive fish, the Chinese sleeper (Perccottus glenii), in the Gulf of Yahorlyk in the Black Sea. On 11 October 2019, a single mature Perccottus glenii female was captured in the Gulf, representing the first record of this fish in Black Sea open waters. This observation of an individual distant 100 km from the nearest freshwater population suggests that the Chinese sleeper may be tolerant to mesohaline waters and thus could spread between the riverine mouths along the coast line. If confirmed, it is highly likely that the Chinese sleeper will invade small rivers in southern Ukraine in the near future.

Common milkweed, Asclepias syriaca L. (Apocynaceae), has become a problematic invasive species in southern regions of Europe and has been added to the list of invasive alien species of concern of the European Union. For a long time, this alien species had not been considered a potential invader in the northern regions of the continent. This study is an attempt to evaluate the potential invasiveness of A. syriaca in the southern part of the Boreal biogeographic region of Europe as by observations made in Lithuania. To this point, the plant has been recorded from 38 sites and the total area occupied by its stands is about 1.29 ha in the country. The size of A. syriaca stands at the different sites varies significantly, from a few individuals to stands covering an area of 0.74 ha. Most frequently, A. syriaca occupies anthropogenic herb stands, unmanaged xeric and mesic grasslands, and was recorded from arable field habitats. In eight of the 17 studied sites A. syriaca sets fruit and produces viable seeds. We suppose that stands setting fruit and producing viable seeds are represented by individuals of several genotypes, whereas some quite large stands are represented by vegetative descendants of one single individual and, therefore, fruit set is absent. Although most of the currently known stands are relics of former cultivation or escaped from areas of recent cultivation, at one site it is considered to be of seed origin. As by the quite large number of A. syriaca localities in Lithuania, its intense vegetative spread, and production of fruits and viable seeds, we predict further future spread and invasion in Lithuania. Thus, A. syriaca should also be treated as a potentially invasive species in other locations of the southern part of the Boreal biogeographical region of Europe.

The alien Ponto-Caspian amphipod Dikerogammarus haemobaphes, that is already well-established in the main rivers of the Belarusian part of the Black Sea basin, was recorded for the first time in the Belarusian part of the Neman River basin (Augustów canal in 2018 and Chornaya Hancha River in 2020). Most likely, this alien amphipod spread naturally and/or was introduced with boat hull fouling from the Polish part of the Narew River (Vistula River basin) via the Augustów canal. This species will invade the Neman River in the very near future.

In 2019, there was an unexpected occurrence of invasive pink salmon in the Faroe Islands (centered at 62°00′N; 06°47′W). Fish were captured by local recreational anglers during the period from late July 2019 to late September 2019. In this brief report, we detail the biological characteristics of the captured pink salmon and discuss the potential of a self-reproducing pink salmon population in the Faroe Islands. This report adds to the overall understanding of pink salmon distribution in the North Atlantic region and mirrors similar reports of odd-year invasive pink salmon populations.

In July 2019, three unusual red algal specimens field identified as Scinaia interrupta were found in Gwaii Haanas, a marine conservation area and heritage site in the Haida Gwaii archipelago, British Columbia. As one of the authors (GWS) has collected relatively extensively in these waters, the collection of these distinctive specimens was unexpected. The DNA barcode COI-5P was used to assess the field identification and the three individuals were closely allied (0–1 bp difference; 0.15%) in a genetic group that was a close sister (7–9 bp difference; 1.1–1.4%) to an earlier collection from southern British Columbia, and a collection from near the type locality in Brittany, France for specimens assigned to S. interrupta. This observation is consistent with separate introduction events for these two populations in British Columbia, although the story may be more complex. Anatomical observations in the laboratory revealed male structures consistent with the Pacific species Scinaia johnstoniae for which there is regrettably no comparative molecular data. Owing to the typically conservative nature of red algal reproductive features, it would be unusual for two such closely related genetic groups to have such divergent male reproduction. For now, we can report on the discovery of a novel Scinaia sp. in Gwaii Haanas tentatively assigned to Scinaia johnstoniae.

Urban insects are continuously introduced to new areas as stowaways or contaminants of trade goods and may, if established in the recipient country, affect society on several levels. The bristletail Ctenolepisma longicaudata, an indoor nuisance pest, was recently detected in Norway and has shown a swift and nationwide upsurge. This study describes its numerical increase and spatio-temporal dispersal into all 18 counties of Norway within a period of 5 years. C. longicaudata showed a distinct 2–3-fold increase per year in measures of submitted pest samples, reported professional pest control cases, insurance claims, news coverage and court cases concerning disputes in transfer of ownership in real estate sales. The insurance claims concerning C. longicaudata are strongly dominated by buildings constructed in the last 15 years and reflect C. longicaudata’s use of the urban habitat, while the 6788 pest control cases pinpoint the magnitude of the problem. The dispersal biology and societal impact of this nuisance pest is discussed in relation to other bristletail species and indoor pests in Norway. The study suggests that an increased import risk, aspects of modern construction and the environmental stability in new buildings may promote populations of C. longicaudata.