Parthenium hysterophorus, commonly known as parthenium weed, is an invasive alien species in Pakistan. There are no specialized natural enemies native to Pakistan that attack the plant species inflicting serious damage and, thereby, keeping it under control. The rust species Puccinia abrupta var. partheniicola, commonly known as the winter rust, is closely associated with its host parthenium weed in its native range in the Americas. This study reports on the first record of the winter rust in Pakistan, with a likely pathway of introduction via India or Nepal. Puccina abrupta var. partheniicola was found to be widely present in several districts of the Punjab and Khyber Pakhtunkhwa Provinces. The sites where the most severe infestations of parthenium weed were observed were in the Lahore District of the Punjab Province. The climatic conditions prevalent in this region during the winter season 2018/2019 were favourable for the winter rust and caused an epiphytotic on parthenium weed. The presence of P. abrupta var. partheniicola marks the second natural enemy of P. hysterophorus recorded from Pakistan and is expected to aid the management of this invasive weed in the country.

Eriochloa villosa is native to temperate Eastern Asia and is an emerging weed in Central Europe. Its current distribution in Central Europe was analyzed using distribution data from the literature and data collected during field trips. In 2019, E. villosa was recorded for the first time in Austria. It was found in a crop field in Unterretzbach in Lower Austria (Eastern Austria). So far, the abundance of E. villosa in the weed communities in Austria and the neighboring Czech Republic is low and thus, its present agricultural impact can be considered limited. However, in Romania and Hungary, the number of records of E. villosa has increased in recent years and it has locally become a troublesome weed. Thus, it is of importance to further monitor E. villosa and to raise awareness among farmers and agricultural advisors.

For proper management of invasive alien species (IAS), it is needed to know species persistence and spread capacity as ignoring them may significantly bias the estimates of species presence. We compared 50 years old historical and current distribution of Telekia speciosa to assess its population change in a restricted area of a chateau park. The aim of this study is to analyse factors that may have shaped the persistence on previous sites, as well as, the spread of the species from historical sites by using repeated sampling. We found that after 50 years Telekia speciosa persisted at 67% sites and has spread to another 381 new sites. Such a level of persistence and rate of spread over a fifty year period goes exceedingly beyond any known records for other IAS.

We recorded the invasive candle bush (Senna alata) for the first time in oases of southern Baja California peninsula in October 2013 and February 2015. Candle bush is likely an escape from residential plantings in this region. Data on density, plant cover, number of pods per plant, and seeds per pod are presented. In the oasis of Santiago, candle bush plant density was low and contained mainly mature plants, which made up 90% of the total population. In the oasis of San José del Cabo, population density was higher, but individuals were mostly shorter than 10 centimeters in height, and 60% of the population consisted of seedlings and young plants. Mature plants were seen mainly in full bloom and early fruiting stages. Candle Bush is invading very dry climates in oasis systems, this is the first documented record of the species invading this kind of wetlands and even starting to invade tropical deciduous forest around arroyos. The introduction pathways and time since the introduction of candle bush into the peninsula are unknown, but no records existed before 2013 when we found the population. We strongly recommend eradicating this invasive species from Baja California oases now, while it is in the early stages of invasion.

We present the first record of the invasive ant Linepithema humile (Mayr, 1868) in the Tuscan Archipelago. Due to its importance as a conservation area in the Mediterranean basin, the archipelago is now protected as a national park (Parco Nazionale dell’Arcipelago Toscano-PNAT). L. humile colonies were found on three of the seven islands studied: Elba, Giglio and Giannutri. The last two islands host abundant populations, whereas the distribution on Elba, although it is probably underestimated, is sparse and spatially localised. No evidence of presence was found on Montecristo, Gorgona, Pianosa and Capraia. Notably, these are islands where public access is more difficult and restricted. Since this ant has a strong impact on native species, strategic plans for future control are crucial to minimise its effect on the already colonised islands and prevent its spread to the other islands.

Specimens of Mochtherus (Coleoptera: Carabidae) found in several locations in Valle del Cauca, Colombia were identified as M. tetraspilotus. This represents the first report of this exotic species, native to Asia, in Colombia and South America. Location data, habitat and photographic record of the species are provided..

The subtropical brown alga, Padina durvillei Bory, is common in the intertidal and shallow subtidal habitats in Baja California, Mexico, in both the Gulf of California and on the Pacific coastline. Here we report the first record of this genus in temperate waters of California, USA, in the heavily urbanized, man-made harbor of Marina del Rey in Los Angeles County, located more than 550 km from its northernmost recorded range. A population of several hundred individuals was found in April 2016 in shallow waters attached to silt-covered concrete adjacent to a public boat ramp. The isolated population has persisted through June 2019. Given that the observed P. durvillei population is located near a heavily trafficked public boat ramp, the alga was likely transported from the Baja California region via recreational boating activities, either attached to the hull of a boat or carried on-board and disposed of in the water. Two other locations in the marina were surveyed in 2016 and 2017 with no Padina individuals found, although further sampling and continued monitoring is needed to ensure the alga has not spread. Ideally, an effort should be undertaken to eradicate this species given its isolated distribution and the relatively small spatial extent of the population.

The Tripoli Harbour, with its cosmopolitan shipping traffic, is a well-known hub for alien molluscs. This is confirmed here by the first report of the Indo-Pacific fissurellid mollusc Diodora funiculata from Libya. While its arrival pathway remains unknown, shipping or natural dispersal from other populations in the Mediterranean Sea may constitute a possible vector. The high number of specimens and shells found suggest an establishment in the area. However, this should be confirmed by additional field work.

The distribution of the Atlantic blue crab Callinectes sapidus is reported from marine, transitional and freshwater environments along the coasts of Sardinia (Italy, western Mediterranean Sea). Professional and recreational fishermen accidentally collected male and female specimens using fishtraps, gillnets or fyke nets depending on the site. This note represents a new contribution to the knowledge on the ongoing colonization of Mediterranean coastal ecosystems by this invasive species.

The non-indigenous mud crab Dyspanopeus sayi (Smith, 1869), native to the western Atlantic, was recorded for the first time in a Sardinian lagoon. The first three specimens of this crab species were collected in the central area of the Santa Gilla lagoon on December 2013. Occurrence of the species was also recorded on December 2018 (102 specimens) and their main morphometric features were quantified. Although there are no certainties regarding the precise arrival date of this alien crab in Sardinia, its presence in the Santa Gilla lagoon might be related to the import of mussels for aquaculture purposes.

A live specimen of American lobster, Homarus americanus, was caught off Croatia, north Adriatic Sea. This is the first record of this species wild-caught in the Mediterranean. The origin of the caught specimen is unknown, yet possible pathways and potential impacts are discussed in the paper.

The Atlantic spadefish Chaetodipterus faber (Broussonet, 1782) belongs to the family Ephippidae Bleeker, 1859 and is a widely distributed species in the Western Atlantic. In this work we present the record of a single specimen of C. faber captured by a professional fisher in Argosaronikos Gulf, Greece. The present sighting, reported through the citizen science project “Is it Alien to you? Share it!!!”, constitutes the first record of this species in the Mediterranean Sea. Given the distance from the Strait of Gibraltar and the absence of any report from western Mediterranean and eastern Atlantic countries, we argue that the specimen is likely to have been released from an aquarium hobbyist. With this record, a total of 27 alien fish species have been likely introduced in the Mediterranean through this pathway, all after year 2000. An increasing trend has been observed and we urge national authorities and relevant stakeholders for their cooperation on increasing the awareness of aquarium trade industry, while we also highlight the effectiveness of citizen science as an early warning system for alien species in the Mediterranean.

The red drum Sciaenops ocellatus (Linnaeus, 1766) was introduced into China from Texas, United States for mariculture purposes nearly three decades ago. The present study provides the first evidence of small red drum juveniles living in a mangrove habitat of the Pearl River Estuary, Southern China. Twenty-eight specimens (4.5–8.0 cm standard length) were caught using traps in February 2016 and April 2016; identification was further confirmed by COI gene analyses. As a large marine predatory fish, the impact of the red drum on native species in Chinese waters is unknown, and the mechanisms of invasion and population establishment in the wild merit further investigations.

The Japanese soft-shelled clam Mya japonica Jay, 1857 is native to the north-western Pacific Ocean but has invaded the northeastern Pacific Ocean, North Atlantic Ocean, Barents Sea and Mediterranean Sea. Here, we confirm its presence in the southern hemisphere using mitochondrial COI, 16S rRNA and nuclear 28S rRNA gene sequences. These analyses permit us to distinguish it genetically from its equally invasive congener, M. arenaria Linnaeus, 1758. We found M. japonica to be well established in one location on the southeast coast of Tasmania.

The highly invasive New Zealand mud snail (Potamopyrgus antipodarum) has established a relatively recent population in central Pennsylvania. The purposes of the work described here were to determine the extent of the invasion, the rate of spread, and the relationship between the abundance of the snail and calcium ion concentration, pH, and conductivity. In two independent sampling efforts, we sampled Spring Creek in Centre County, Pennsylvania, at various times from 2014 to 2018. We also sampled tributaries of the stream as well as the larger watershed of Bald Eagle Creek. In addition, we established sites to monitor other streams that are likely to be frequented by recreational water users (a known snail dispersal agent). We found that compared to the geographic distribution in 2014, the snail increased its geographic range, and snail abundance increased at most locations. We also found evidence of expansion out of the Spring Creek watershed into the larger Bald Eagle Creek watershed at two locations in 2018. Snail abundance was positively related to pH and conductivity in 2017. We recommend that streams in central Pennsylvania be routinely monitored for the presence of this species, especially those regularly visited by recreational water users and that have chemical characteristics favorable to the NZMS.

The Australian redclaw crayfish, Cherax quadricarinatus, is a popular aquaculture crayfish that has been introduced around the world. Here we report the first occurrence of the species in the United States in Lake Balboa, Los Angeles, California. The impacts of this species are largely unknown, and further research is needed to determine the species’ effects on native ecosystems. Sampling is needed to evaluate the population status in Lake Balboa to determine to what extent the species has spread in the greater Los Angeles River basin.

First sighting of the non-indigenous spiny-cheek crayfish Faxonius limosus (Refinesque, 1817) in Estonia was registered in October 2017 in the pre-estuary of the Pärnu River which flows into the Baltic Sea. This indicates the continuing expansion of this species in Northern Europe. The detection site is about 70 km from the border of Latvia, a country where F. limosus is already present, but in the studied rivers which flow to the Gulf of Riga between the Pärnu River and Latvian border, no F. limosus was found. This suggests that a human-assisted introduction of the species into the Pärnu River is very likely.

The Black Acara, Cichlasoma bimaculatum (Linnaeus, 1758), was first reported as introduced to Florida in 1965. Native to Venezuela, Guyana, Suriname, western French Guiana, and northern Brazil, the species is now distributed throughout Florida’s southern peninsula. Examination of live and preserved acara from Central Florida, heretofore identified as Black Acara, reveal the presence of an additional acara species, the Chanchita, Cichlasoma dimerus (Heckel, 1840). The Chanchita is native to Bolivia, Paraguay, Uruguay, southern Brazil, and northeastern Argentina. Despite similarities, Black Acara and Chanchita can be distinguished by number of anal-fin spines, body and fin color, caudal-fin pattern, and head, nape, and upper-flank scale-rim pigment. The Chanchita is established in multiple Central Florida drainages with the earliest known record from July 27, 2000. The Chanchita has not been found to co-occur with the Black Acara. The presence of Chanchita in more than one Central Florida spring and the widespread distribution of this previously unreported introduced species may be of concern to natural resource managers.

The introduction and spread of non-native species poses a significant threat to the health of freshwater ecosystems, and has recently been identified as the single biggest danger to threatened species survival in Australia. Notwithstanding, the importation, trade and keeping of exotic and potentially invasive freshwater fishes in Australia is significant, resulting in greater propagule pressure and higher risk for deliberate or incidental release into native waterways. The jaguar cichlid (Parachromis managuensis) is an invasive cichlid that has established non-native populations in many countries throughout the world. In December 2014, the Department of Agriculture and Fisheries in Queensland was notified of an incursion of jaguar cichlids in a stormwater retention dam in the Pioneer River Catchment, Mackay, Queensland. Rotenone was applied to the dam in January 2015, and around 200 jaguar cichlid specimens at various life history stages were destroyed. Follow up surveys into mid-2015 did not detect the presence of any jaguar cichlid in the dam or in nearby creeks. In September 2017, the Department was notified of a wild capture of a mature jaguar cichlid in Fursden Creek, 1.5 km from the original incursion site. Follow up surveys in 2018/19 have also detected jaguar cichlid juveniles in surrounding tributaries, indicating successful establishment and naturalisation of the species in Australia for the first time.

In this article we report the first invasion of Rüppell’s weaver (Ploceus galbula) into the Palearctic biogeographic zone. This research documents the introduction and spread of Rüppell’s weaver in the Eastern Province, Saudi Arabia. Because the Rüppell’s weaver are not strong fliers, their introduction is almost certainly caused by escapees and deliberate releases of birds brought in by pet trade. Subsequently, Rüppell’s weavers were able to breed and spread, feeding on the seasonal crops, while exhibiting the ability to utilize variable food sources. After the first introduction in the Al-Qatif city, the weavers spread north and south. This report highlights the potential ecological, economic and social impacts of the weaver’s invasion in the Eastern Province of Saudi Arabia. Lastly, the importance of a comprehensive study assessing the effects the Rüppell’s weaver has in these invaded habitats is highlighted.