The genus Erigeron (Asteraceae) includes several widely distributed invasive species for which data on chromosome numbers and cytological variation are lacking in many parts of their introduced range. In this study, we targeted five alien Erigeron taxa occurring in Poland to test their chromosome numbers in the context of cytological diversity and invasiveness. In addition, we included three native taxa of the E. acris s. l. complex which are also cytogeographically poorly recognised. To count chromosomes, we made stained microscopic preparations from root tip samples obtained from seedlings or mature plants. Among alien taxa, we documented diploids (2n = 2x = 18) in E. canadensis and E. ×huelsenii (a hybrid between E. acris and E. canadensis), triploids (2n = 3x = 27) in E. annuus, triploids and tetraploids (2n = 4x = 36) in E. strigosus, and hexaploids (2n = 6x = 54) in E. sumatrensis. In the case of native taxa, we found diploids (2n = 2x = 18) in E. acris subsp. acris, E. acris subsp. podolicus and E. muralis. We also showed that the karyotype of E. ×huelsenii includes two sets of chromosomes differing in size, reflecting the difference in the amount of nuclear DNA between its parental species. However, this hybrid appears to be a weak competitor due to its sterility, lack of vegetative propagation and short lifespan. Moreover, our results confirm that E. strigosus can be cytologically diverse even in one small geographical region in its introduced range. Further studies are needed to prove the effects of hybridisation and polyploidy on competitive abilities in alien Erigeron species.

Amorpha fruticosa is a non-native invasive species of Slovak flora spreading along waterways. In the past, it was planted to strengthen road embankment soil. These plantings on the edges of motorways and expressways are potential seed sources. A survey of the distribution of A. fruticosa along all motorways and expressways in Slovakia was carried out in June 2023 (tracking while driving, counting A. fruticosa sites). In total, 519.42 km of motorways and 252.19 km of expressways were covered in both directions. The species was recorded on 40.01% of motorway and expressway sections. The highest frequency of occurrence was recorded in warm regions, at elevations up to 300 m a.s.l. (1900 records, 99.16%) and along the oldest sections of motorways and expressways (completed by the year 2000 – 1833 records, 95.67%). At higher elevations in northern Slovakia, the occurrence of the species was rare (16 records, 0.84%). Amorpha fruticosa spreads from existing plantations to nearby surrounding plant communities. Its spread into the open landscape is effectively prevented by regular mowing, mulching, grazing or ploughing of stands on cultivated agricultural land around road embankments.

A species from the genus Andropogon, that has been known since 2011 from the island of La Palma (Canary Islands, Spain) and that was initially attributed to the putatively native species A. distachyos, is here identified as the African weed A. abyssinicus. The identification, based on morphological characteristics, was further supported by molecular data and ploidy estimation. In La Palma, A. abyssinicus is locally naturalized along roadsides and on slopes of ravines between La Dehesa and El Dorador (Santa Cruz de La Palma). The differentiation from morphologically similar species, in particular A. amethystinus and A. distachyos, is discussed. Until now, only one species of Andropogon was reported from the Canary Islands, A. distachyos, a widespread species from subtropical regions of the Old World. However, its presence in the archipelago requires confirmation, as apparently no herbarium material is available that unequivocally testifies its presence there. The limited bibliographic and other references are briefly discussed.

We report the first record of Tarenaya spinosa (Jacq.) Raf. (spiny spider flower) as a new addition to the naturalized alien flora of Iran. Spiny spider flower is native to South and Central America and widely naturalized in the paleo-tropics (south Africa and Asia). This species was intentionally introduced to Iran in the last decade of the XX century and cultivated as an ornamental plant due to its large, peculiar, and colorful flowers. It escaped from cultivation and gradually increased its alien range in the surrounding areas, by seeds, without any direct human intervention. The UNESCO-world-heritage site Hyrcanian forests (northern Iran) includes a unique forest ecosystem which is potentially threatened by the naturalization of many alien and invasive species including this new recorded alien. Considering the potential negative impacts of this new alien species on the native biodiversity and its high reproductive potential and spread capacity, we highlight the importance of preventing new introductions, and prioritizing practices for eradication and control before it could become widespread and unmanageable.

We report the first evidence of establishment of the palm borer moth Paysandisia archon (Burmeister, 1879; Lepidoptera: Castniidae) in southern Switzerland. Originally from South America, P. archon has been increasingly spotted in southern Europe in recent years, where it poses a substantial threat to palms as its larvae bore into their meristem, feeding on the inner tissues, weakening the plants, and, in most cases, leading to their demise. We conducted non-systematic surveys and compiled reports of sightings of P. archon and its attributed damages, which were then all stored in an online database. Sightings and damage caused by P. archon have been confirmed across multiple locations in southern Switzerland, with major infestations reported on the northern shore of the Lago Maggiore and affecting various palm species. While P. archon poses a major threat to cultivated palm specimens that are iconic for the (sub)urban landscape of southern Switzerland, it may also help control the undesired spread of the invasive Chinese windmill palm Trachycarpus fortunei in the peri-urban forests.

The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive alien insect pest in Africa originally from Central America. Although it is a pest of mainly stored maize grain and dried cassava roots, the larger grain borer is polyphagous, damaging a wide variety of other staple grains and non-agricultural forest and household products (e.g., wood and/or trees, leather, rubber). To-date, the pest has spread to over 21 countries in Africa since its first introduction in the 1970s. Stored maize grain losses have since doubled in these countries. In Southern Africa, the pest was first reported in Malawi (1991), then Zambia (1993), Namibia (1998), South Africa (1999), Zimbabwe (2005), and Mozambique (2007). Specimens of the pest sampled through pheromone baited traps on the outskirts of Gaborone, Botswana were morphologically identified and confirmed using molecular sequencing. Therefore, we make a first report on the occurrence of the larger grain borer in Botswana and recommend urgent and concerted efforts to monitor the pest, update databases on the extent of its geographical distribution, host range (crop and non-crop products, including its prospective biosecurity threats and risks), socio-economic impacts and strategies for containing and managing this invasive quarantine pest.

The Black, Azov and Caspian Seas are donor hotspots for non-native species, with many species from the region highly tolerant of abiotic stressors and able to successfully establish, spread and exert impacts around the world. Here we document a new introduction of the bloody red mysid shrimp, Hemimysis anomala G.O. Sars, 1907. Discovered for the first time in January 2023 in Lake Stechlin, Germany, at high densities, many questions surround its potential impacts in this deep, formerly oligotrophic, now meso-eutrophic lake of major geological, cultural and ecological importance. Using molecular and morphological identification, the identity of H. anomala from two sites in the lake was confirmed. Unlike other mysids normally detected over deeper waters in lakes at night, H. anomala has so far only been detected near the surface and at depths shallower than 30 m, but during both night and day, in winter. We outline vital areas for future research and the need for dedicated sampling methods by also highlighting a case study from Lake Müggelsee, Berlin, where the species has been known to exist for over 20 years without being caught in regular plankton tows.

Anthropogenic activities have significantly influenced the global distribution of aquatic organisms, with non-native species establishing new populations in diverse ecosystems. This study focuses on the copepod Thermocyclops taihokuensis (Harada, 1931), native to Asia, which has become a notable invader in East European waters. The research delves into the species’ diagnostic morphological features, expansion, and emphasizes its ecological implications. Investigations of zooplankton assemblages in Central Europe reveal the expansion of T. taihokuensis, with new records in small water bodies connected to the Danube River system in Hungary and the lower Odra River in Poland. The closest geographical occurrence of the species is known from the Don River. The expansion of T. taihokuensis raises concerns due to its potential to outcompete native copepod species and impact local biodiversity. Monitoring zooplankton communities in newly colonized areas is crucial to track changes in assemblages.

We describe the occurrence of two unusually coloured crayfish individuals in two different locations in northwestern Italy (lakes Orta and Comabbio). They represent the first record in Italy of a marbled colour morph of Procambarus clarkii. Species assignment through morphological analyses was confirmed by molecular identification. Different body parts from the adult marbled coloured male and female, together with eggs and juveniles were analysed and blasted in GeneBank. All the sequences were identified as P. clarkii, with a query coverage ≥ 99.0% and a percentage identity ≥ 99.7%. Based solely on external appearance, this new morphotype may lead to misinterpretation of taxonomic identification, being this colour morph very similar to the Marmorkrebs P. virginalis. A marbled female of P. clarkii could be wrongly attributed to Marmorkrebs when identification keys and molecular taxonomy are not considered to complement each other. The marbled morph of P. clarkii not only illustrates how varicoloured are the members of the family Cambaridae, but it also suggests that marbled colour alone is inadequate to identify a species. Therefore, it is recommended to consider this new colour in the morphological identification of the adult red swamp crayfish P. clarkii. The approach that integrates both molecular and morphological information improves promptly species taxonomy towards timely and appropriate management measures.

This paper presents the first overview of aquatic alien invertebrate species (AIS) in the three major river basins (Tigris, Euphrates and Shatt Al-Arab) in southern Iraq. The results are based on field studies undertaken in 2021 and 2022. Thirteen AIS have been recorded. Three of them are “old invaders” (first recorded in the early 19th century to 1970), two species are “intermediate invaders” (first recorded between 1970 to 1990) and eight are “new invaders” (first recorded after 2000). The number of AIS has been growing substantially since 2000. The highest AIS number is recorded in the Shatt-Al-Arab (11 species), a middle number in the Euphrates basin (10 species) and the lowest number in the Tigris (6 species). On the whole, 31% of the recorded species originate from Southern America or Northern America, 23% from Asia, 8% from Southern Europe, Africa and Southern Asia, the Atlantic Ocean, Africa and Northern America, 7% from New Zealand, and the Caspian Sea. Most AIS were likely introduced unintentionally. The study demonstrated that many AIS, like e.g. Macrobrachium nipponense, have been collected both from the upper and the lower sections of the study rivers providing successful examples of aquatic AIS that can establish populations in fresh and brackish waters. The compiled species list is a first step toward the management of the invasive species that are now present in rivers of southern Iraq. It provides a basis for the creation of monitoring programs, early detection initiatives, and quick responses to prevent future invasions in the Tigris-Euphrates and Shatt Al-Arab basins.

Ficopomatus uschakovi originally described from Sri Lanka was recently reported as an alien species introduced to the Pacific and Atlantic coasts of Mexico. In the present study, mitochondrial DNA (Cytochrome oxidase b) sequence data were used to confirm that specimens from both coasts of Mexico and Miami, Florida belong to the same genetic species, thus supporting invasive status of the species in America. However, sequences of the American F. uschakovi were also identical to the single cytb sequence of a specimen from Thailand deposited to GenBank under the name Ficopomatus macrodon. Re-examination of the voucher showed that its operculum bears of a row of chitinous opercular spines typical for F. uschakovi instead of a smooth, concave endplate of F. macrodon. DNA sequences of F. macrodon from the type locality in India (Cochin Backwater) were also significantly different from that of “F. macrodon” in GenBank. Molecular data showing the same genetic species found in distant and disjoint biogeographic areas supports the hypothesis that F. uschakovi in America is a recent incursion from South-East Asia, but material from the type locality (Panadura, Sri Lanka) is needed to confirm the species identity and invasive pathways. The study stresses the importance of morphological vouchers deposited in properly curated museum collections for molecular studies, in particular for bioinvasion research.

The first documented occurrence of the crucifix crab Charybdis feriata in the Adriatic Sea is reported here based on a single specimen captured off Senigallia in October 2023. Evidence from previously published records in the Mediterranean Sea, along with the present finding, suggests that this non-indigenous species, native to the tropical Indo West-Pacific belt, is being repeatedly introduced by shipping, likely concealed within the hull space of sea-chests. Conversely, the transport of larvae or early crab stages with ballast waters seems unlikely due to the thermal regimes of the recipient seas and the size of the recorded adult crabs.

The black bullhead Ameiurus melas is an invasive fish species that has been introduced into Europe. In this account, proteocephalid tapeworms of the subfamily Essexiellinae, which are specific intestinal parasites of ictalurid catfishes in North America, are reported from A. melas from the Danube River in Slovakia. Molecular phylogenetic analysis based on sequences of the 28S rRNA and COI genes revealed that the tapeworms from Slovakia are almost identical to Corallotaenia sp. 1 of Scholz et al. (2020) from A. melas in Oklahoma and Wisconsin, USA and are morphologically similar. This is the second report of the occurrence of essexielline tapeworms in Europe after 35 years. The relatively common occurrence of these tapeworms in black bullheads from one of the largest European river that connects Western and Eastern Europe is alarming, and their further spread throughout Europe is likely.

The spread of invasive fish species poses a major threat to native aquatic communities and ecosystems. Amur sleeper is one of the most rapidly spreading invasive fish in Eurasia. In this study, we used environmental DNA (eDNA) metabarcoding to sample fish assemblages in various types of water bodies in a protected floodplain of the Middle-Danube section in Hungary, with a special attention to the distribution patterns and early detection of the invasive Amur sleeper. The species was detected in one of the 15 water bodies sampled. At this site all samples were tested positive for the species and the detection was additionally confirmed by electrofishing. This is the first detection of the species in this Danubian floodplain. Since the area maintains a high level of biodiversity with numerous protected and rare aquatic invertebrates and vertebrates, we highlight the need of urgent management actions to prevent the further spread of Amur sleeper within and outside of the floodplain. Additionally, we provide a further example of the practical application of eDNA methods in the early detection of invasive species.

Bristlenose catfish, specifically Ancistrus chagresi Eigenmann & Eigenmann, 1889 and Ancistrus sp. have been found in the Ciliwung watershed, Indonesia. These two species are alien fishes from Central and South America. Out of the six specimens, five Ancistrus chagresi had a standard length of 35.76–71.67 mm, while one Ancistrus sp. measured 73.43 mm. The presence of these two species in Indonesian waters could lead to them becoming invasive and consequently impacting native species. It is imperative to handle both Ancistrus species carefully to prevent their population from growing uncontrollably.

Understanding changes in the status of invasive species is important to managers in order to prevent or minimize impacts to native communities. Out of the four invasive carp imported to the U.S. from Eastern Asia, black carp Mylopharyngodon piceus have been generally overlooked due to the difficulty in capturing these fish even using targeted efforts. Because of this, limited resources have been channeled towards managing this species. Concerns over the expansion of black carp have been expressed, but direct evidence of reproduction in U.S. waters was lacking until young of year black carp were caught in tributaries of the Middle Mississippi River in 2015. This remained the known extent of the naturalized invasion until fish community surveys conducted in the fall of 2022 and 2023 documented young of year black carp in three oxbow lakes connected to the mainstem Lower Mississippi River. These collections provide evidence for increased population growth and exhibit expanding threats to the diverse mussel communities native to the Lower Mississippi River basin.

The transfer of species between river basins has been recognized as one of the principal drivers of the loss of biodiversity and changes in aquatic ecosystems. The impacts caused by invasive species include predation, habitat degradation, competition, hybridization, and the transmission of diseases. Brycon amazonicus, known in Brazil as the matrinxã or jatuarana, is a fish endemic to the Amazon basin. It is cultivated in fish farms throughout Brazil and is an important fishery resource. Due to its popularity for fish farming, there have been numerous reports of individuals escaping into the natural environment. Specimens of Brycon amazonicus were captured during surveys of the Santana River, upstream from a reservoir in the Brazilian state of Mato Grosso, central Brazil. The Santana originates in the Chapada do Parecis and flows into the Paraguay River basin. Morphological analyses and cytochrome c oxidase subunit I (COI) gene sequences confirmed the taxonomic identification of the specimens. The present study provides a new record of the species, expanding its known area of occurrence.

Caribbean islands are particularly vulnerable to biological invasions. We update the distribution of the highly invasive mourning gecko, Lepidodactylus lugubris, in Guadeloupe, French Antilles, based on both extensive and intensive surveys conducted in spring 2022. Among 160 prospected sites, the probability of occurrence of the species did not differ significantly between urban, surburban/rural, and natural habitats. However, its density was significantly lower in the urban habitat compared to both the periurban habitat and the natural habitat. The occurrence and relative abundance of the mourning gecko was independent of that of the tropical house gecko, Hemidactylus mabouia, another nocturnal gecko introduced earlier in Guadeloupe. Finally, comparison with a previous study conducted in 2018 at a hotel resort suggests a two-fold increase in the abundance of the species in four years. We recommend investigating the ecological impact of L. lugubris in Guadeloupe to inform management decisions.

In this study, we investigate the morphological identity and genetic diversity of the common wolf snake Lycodon capucinus in Hong Kong, so as to assess its nativeness in the territory and neighbouring region. Remarkably, all Hong Kong samples and a single sample from neighbouring Guishan Island of Guangdong Province formed a single lineage and showed no genetic divergence and phylogeographical structure despite being collected from several different places and island. Together with literature review data on the historical records and distribution pattern of the species in Hong Kong and wider southern China, we conclude that the Hong Kong population is not native, but has been introduced to the territory in or before 1880s. We also discussed the records of L. capucinus from mainland China and its nativeness in the country. Our analysis suggested that the native population only occurs in western part of Yunnan Province bordering northern Myanmar, while the 150-year long historical record in the coastal city of Xiamen of Fujian Province should belongs to introduced individuals. Future in-depth studies are needed to investigate its impacts on the native fauna and ecosystems in Hong Kong, and formulate relevant management plans eliminate its impacts on native species, if any. We also urge the relevant authorities across the border in the neighboring cities of Shenzhen, Zhuhai, and Macau SAR, to pay close attention to the potential introduction and/or expansion of this alien species from Hong Kong, and undertake prompt actions to remove any introduced snakes found at the early stage.

Invasive rodents are widely distributed worldwide and are responsible for significant agricultural and urban infrastructure losses. They are hosts of numerous zoonotic pathogens. In the southeastern region of Mexico, only Rattus rattus has been recorded. The presence of R. norvegicus in Chiapas, in San Cristobal de Las Casas, a medium-sized city in Southeastern Mexico, is reported here for the first time with genetic evidence, through a DNA barcode analysis performed using the cytochrome c oxidase subunit I (COI) gene. Given the economic and health importance of these rodents, it is crucial to know their distribution and set an ecological knowledge baseline.