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Simple Summary: The round goby is considered one of the most widespread Ponto-Caspian invasive species, which poses a threat to ecosystems and food web alterations. While it is known for direct predation, its interactions with native higher predators and its feeding behaviour upon their presence remain unclear. Therefore, we investigated how the exposure to chemical alarm cues emitted by conspecifics and the odour of a native predator, the European eel, affects the round goby's feeding activity. Surprisingly, the gobies did not exhibit any pronounced threat sensitivity to both types of chemical stimuli, which was observed in unchanged food consumption probability and gut evacuation rates. The obtained outcomes suggest boldness, great efficiency in food processing, and a potential competitive advantage over native counterparts when colonising new ecosystems, irrespective of local higher predator presence. The round goby Neogobius melanostomus is a notoriously invasive fish originating from the Ponto-Caspian region that in recent decades has successfully spread across the globe. One of its primary impacts is direct predation; in addition, when entering new ecosystems, the round goby is likely to become a food resource for many higher native predators. However, little is known either about the indirect effects of predators on the round goby as prey or its feeding behaviour and activity. The non-consumptive effect of the presence of higher native predators presumably plays an important role in mitigating the impact of non-native round gobies as mesopredators on benthic invertebrate communities, especially when both higher- and mesopredators occupy the same habitat. We tested the food consumption probability and gut evacuation rates in round gobies in response to chemical signals from a higher predator, the European eel Anguilla anguilla. Gobies were placed individually in experimental arenas equipped with shelters and exposed to water from a tank in which (a) the higher predator had actively preyed on a heterospecific prey, earthworms Lumbricus sp. (the heterospecific treatment; HS); (b) the higher predator had fed on round gobies (the conspecific treatment; CS); or (c) the water was provided as a control treatment (C). To ensure exposure to the chemical stimuli, this study incorporated the application of skin extracts containing damaged-released alarm cues from the CS treatment; distilled water was used for the remaining treatments. No significant differences were observed in either the food consumption probability or gut evacuation rate in the tested treatments. Despite the lack of reaction to the chemical stimuli, round gobies did exhibit high evacuation rates (R = 0.2323 ± 0.011 h−1; mean ± SE) in which complete gut clearance occurred within 16 h regardless of the applied treatment. This rapid food processing suggests high efficiency and great pressure on resources regardless of the presence or not of a higher predator. These findings hint at the boldness of round gobies, which did not exhibit any pronounced threat sensitivity. This would seem to suggest great efficiency in food processing and a potential competitive advantage over local native species when colonising new ecosystems, irrespective of the presence of native predators. Our study did not detect any non-consumptive effect attributable to the higher predator, given that the feeding activity of the invasive round goby was not altered. [ABSTRACT FROM AUTHOR]

Ships' ballast water and sediments are vectors that contribute to the unintentional spread of aquatic non-native species globally. Ballast water management, as well as commissioning testing of ballast water management systems and compliance monitoring under the regulations of the International Maritime Organization (IMO) aimat minimizing the unwanted spread of organisms. This study compiles data for treated ballast water samples collected and analyzed from 228 ships during 2017-2023. The samples were collected from the ballast discharge line or directly from the ballast tank for enumeration of living organism concentrations in the categories of =50µm and <50 to =10µm -sized organisms, as well as indicator microbes in comparison to the ballast water performance standard of the IMO (Regulation D-2). In addition, several ship-specific factors were examined to infer potential factors affecting compliance rates. Nearly all ships were compliant with the ballast water performance standard for indicatormicrobes and <50 to =10µm -sized organisms, whereas almost half of all samples exceeded the limit of ten viable organisms m-3 for the =50µm -sized organisms. Compliance testing results did not differ significantly between sampling years, indicating that compliance rate did not change through time. The rate of compliance was higher for commissioning testing than compliance testing. Clear ship-or system-specific factors that lead to compliance or non-compliance were not detected, even though type of ballast watermanagement system, filter mesh size associated with the systemand source of ballast water affected compliance significantly either for the samples taken from the discharge line, or ballast tank. As compliance did not improve significantly over time, compliance testing of ships' ballast water should be undertaken to ensure that the systems remain operational after commissioning and ships meet requirements of the D-2 standard. Furthermore, the study outcomes promote further research on the efficiency of filter mesh sizes and different filtration units associated with ballast water management systems, to improve mechanical removal of larger organisms. Finally, as several ships exceeded the compliance limit by hundreds or thousands of living organisms, technological advancements and operational measures may be needed to improve the overall reliability of ballast water management. [ABSTRACT FROM AUTHOR]

Broadleaf water milfoil (Myriophyllum heterophyllum) is an emerging invasive alien plant in Europe, and thus a priority for European Union (EU)-level surveillance, monitoring, and eradication. This species is native to North America and threatens aquatic ecosystems by creating dense stands that can fill an entire water body, leading to high economic costs and the loss of native biodiversity. Although its presence in Portugal is not reported, the species has already been established in several European countries, including neighboring Spain. In this study, we assessed the risk of invasion by this species in mainland Portugal by jointly considering environmentally suitable areas and the risk of human-mediated introduction. Environmental suitability was estimated using MaxEnt, which relates the known species distribution to climate, topography, and soil variables. The model achieved a mean area under the curve value of 0.96 ± 0.008 and identified the mean temperature of the warmest quarter as the most relevant variable for explaining the species distribution (67.2 %). Predictions from the model indicated that the peaks of suitability values were distributed mainly in temperate climate regions along central and northern coastal areas in Portugal. The risk of introduction was estimated by mapping and calculating the spatial density of the aquarium stores. Jointly considering environmental suitability and risk of introduction, we observed that hotspots at risk of invasion are concentrated on the Portuguese central and northern coasts and in the two main metropolitan areas, Lisbon and Porto. Several risk hotspots fall within protected areas and sites designated under the EU Habitats Directive, comprising water bodies of high significance for maintaining local vegetation and fauna. Therefore, it is necessary to take measures to reduce the risk of invasion by this species, namely, surveillance and monitoring efforts confirming its absence in the national territory and preventing its future arrival.

In recent years, cyanobacterial invasions have increased in European temperate lakes. Climate warming is highlighted as a key driver of the distribution and establishment of alien cyanobacteria, and water bodies in poor ecological status, characterized by meso-eutrophic conditions, are underlined as a suitable habitat for invasion. The establishment of newly arrived species is directly related to fluctuating physicochemical factors such as temperature, and nutrient concentrations, especially phosphorus and nitrogen, or biotic factors such as competition. Cyanobacterial invasions can have profound ecological impacts, such as displacing native species, causing the biodiversity loss of local communities, and modifying the ecosystem’s cyanotoxins profile. This study presents the occurrence of four alien bloom-forming potentially toxic cyanobacteria - Chrysosporum bergii, Cuspidothrix isstaschenkoi, Raphidiopsis raciborskii and Sphaerospermopsis aphanizomenoides - in the northern parts of their current range in temperate Europe and provides insights into their ecology. Special attention was paid to the lakes of Lithuania (Simnas, Jieznas and Gineitiškės), which is the northernmost location of distribution zone for some alien cyanobacteria and provides as a dispersion route to Norther Europe via the continental area. We i) described dynamics of indigenous cyanobacteria community invaded by alien cyanobacteria; ii) assessed concentrations of cyanotoxins in field and culture samples, and suggested toxin producers; and iii) detailed the correlation between the biomass of alien cyanobacteria and environmental conditions. These species were found in three human-affected shallow hyper-eutrophic lakes during warm period of the year; however, their biomass was low. We assume that present temperatures do not limit the occurrence of these alien species but are insufficient for their successful proliferation. In addition, we provided the first evidence of anatoxin-a production by isolated strains of C. issatschenkoi in Lithuania. Alien cyanobacteria were detected at an early stage of their development, however, a rise in global temperatures and the spread of strains with toxigenic potential could lead to increased proliferation and further northward expansion of these alien species.

The attractiveness of a species influences human perceptions and attitudes toward it, while flagship species play a significant role in shaping public conservation interests. This research investigated how humans perceive the attractiveness of and their willingness to protect vertebrate and invertebrate aquatic representatives. The study focused on endangered and invasive fish and crayfish species presented to the participants through pictures shared via an online questionnaire. Participants rated the attractiveness of the species and indicated their willingness to protect them using a 7-point scale. The analysis was conducted based on 118 responses from men and women whose backgrounds varied in terms of their age, education, and knowledge regarding biological invasions. The findings indicate that the perceived attractiveness of a species was the primary factor influencing the participants' willingness to protect the species: the more attractive a species was rated, the greater the willingness to protect it. Overall, endangered fish and crayfish species received higher willingness-to-protect scores than invasive species, with crayfish species being perceived as significantly more attractive than fish. Using attractive or flagship aquatic species, such as crayfish, in the conservation efforts of endangered freshwater taxa can enhance public, stakeholder, and policymaker awareness, thereby potentially contributing to the conservation and restoration of freshwater ecosystems and the protection of native biota. [ABSTRACT FROM AUTHOR]

Ships’ ballast water and sediments are vectors that contribute to the unintentional spread of aquatic non-native species globally. Ballast water management, as well as commissioning testing of ballast water management systems and compliance monitoring under the regulations of the International Maritime Organization (IMO) aim at minimizing the unwanted spread of organisms. This study compiles data for treated ballast water samples collected and analyzed from 228 ships during 2017–2023. The samples were collected from the ballast discharge line or directly from the ballast tank for enumeration of living organism concentrations in the categories of ≥50µm and

The round goby Neogobius melanostomus is a notoriously invasive fish originating from the Ponto-Caspian region that in recent decades has successfully spread across the globe. One of its primary impacts is direct predation; in addition, when entering new ecosystems, the round goby is likely to become a food resource for many higher native predators. However, little is known either about the indirect effects of predators on the round goby as prey or its feeding behaviour and activity. The non-consumptive effect of the presence of higher native predators presumably plays an important role in mitigating the impact of non-native round gobies as mesopredators on benthic invertebrate communities, especially when both higher- and mesopredators occupy the same habitat. We tested the food consumption probability and gut evacuation rates in round gobies in response to chemical signals from a higher predator, the European eel Anguilla anguilla. Gobies were placed individually in experimental arenas equipped with shelters and exposed to water from a tank in which (a) the higher predator had actively preyed on a heterospecific prey, earthworms Lumbricus sp. (the heterospecific treatment; HS); (b) the higher predator had fed on round gobies (the conspecific treatment; CS); or (c) the water was provided as a control treatment (C). To ensure exposure to the chemical stimuli, this study incorporated the application of skin extracts containing damaged-released alarm cues from the CS treatment; distilled water was used for the remaining treatments. No significant differences were observed in either the food consumption probability or gut evacuation rate in the tested treatments. Despite the lack of reaction to the chemical stimuli, round gobies did exhibit high evacuation rates (R = 0.2323 ± 0.011 h−1; mean ± SE) in which complete gut clearance occurred within 16 h regardless of the applied treatment. This rapid food processing suggests high efficiency and great pressure on resources regardless of the presence or not of a higher predator. These findings hint at the boldness of round gobies, which did not exhibit any pronounced threat sensitivity. This would seem to suggest great efficiency in food processing and a potential competitive advantage over local native species when colonising new ecosystems, irrespective of the presence of native predators. Our study did not detect any non-consumptive effect attributable to the higher predator, given that the feeding activity of the invasive round goby was not altered.

Suckermouth armored catfish (Pterygoplichthys disjunctivus) is one of the most widespread invasive species in Vietnam. However, it is relatively unknown how the species underwent its divergent adaptations to varying local conditions and habitat types, an understanding of which is essential for managing its invasion in Vietnam. We addressed this by analyzing a large number of fish (662 samples) collected in lotic (Dinh River) and lentic (Suoi Trau Reservoir) habitats in southern Vietnam during one year. The allometric growth patterns estimated by von Bertalanffy growth functions were L t = 483 1 − e − 0.71 (t − 0.40) in Dinh River and L t = 346 1 − e − 1.01 (t − 0.62) in Suoi Trau Reservoir. The estimated fish ages were 2.9 to 4.2 years old with an average total length from 206.10 ± 2.09 mm in Suoi Trau Reservoir to 319.22 ± 3.29 mm in Dinh River. The percentage of fish with matured ovaries peaked in August (100%) and was lowest in February (<10%), indicating that these fish breed nearly all year round. The main reproductive season is April–October, with a peak in July–August, as indicated by the gonado-somatic index and monthly changes in the percentage of matured fish. The lengths at 50% maturity were 234.3 and 179.7 mm for females from lotic and lentic habitats, respectively. Lotic fish had a fecundity (4812 ± 383 oocytes/ind.) which was five times greater than that of lentic fish (841 ± 91 oocytes/ind.); however, the relative fecundity of the fish was not statistically different between the two habitats (≈13 oocytes/g). This result was consistent with the larger oocytes: 2.95 ± 0.04 and 2.58 ± 0.01 mm for fish from Dinh River and Suoi Trau Reservoir, respectively. The faster growth and bigger fish with higher fecundity in the lotic habitats suggest that their population growth can accelerate more quickly, potentially affecting local communities more than those in lentic habitats. Our study sheds light on substantial phenotypic divergences in the reproduction and growth of the suckermouth armored catfish between lotic and limnetic habitats in Vietnam. [ABSTRACT FROM AUTHOR]

Citizen science is emerging as a powerful tool for the early detection of biological invasions. The exotic pet trade has been deemed as the most significant cause of establishment for reptiles, and among them, turtles have the highest number of introduction events. In Europe, at least 13 species of alien freshwater turtles have been recorded in the wild. In Greece, only two species of alien turtles have been reported, namely the American pond slider Trachemys scripta and the Florida cooter Pseudemys floridana. In this study, we provide an updated checklist of the alien freshwater turtles recorded in Greece, using citizen science, personal observations, and literature. Our results provide the first records for the country of five species, namely the Florida red-bellied cooter Pseudemys nelsoni, the Eastern river cooter Pseudemys concinna, the Chinese stripe-necked turtle Mauremys sinensis, the Chinese soft-shelled turtle Pelodiscus sinensis, and the Common snapping turtle Chelydra serpentina and new localities for T. scripta. Similar to the myth of the Lernaean Hydra (i.e., for every head chopped off, more would regrow), the pet turtle trade has been proven to have multiple heads. [ABSTRACT FROM AUTHOR]

Submerged macrophyte Elodea canadensis Michx. is a non-native species to Turkey where it was first recorded in 1982. In this study, we aim to provide the current distribution of E. canadensis in Turkey with notes on its invasion history and ecology. We performed field studies to measure the physical and chemical parameters of the invaded lakes. Our study is based on new field works, herbarium specimen examination and literature survey. As a result of our findings, E. canadensis has invaded 15 wetlands in eight water basins of Turkey. Eleven of the invaded wetlands, including the largest freshwater lake of Turkey have protection forms ranging from national parks, nature parks to nationally/locally protected areas. Type of the wetlands are also diverse, like drainage canals, ancient pools, karstic, crater, tectonic and alluvial set lakes with trophic status from oligotrophic to eutrophic. Physico-chemical parameters measured in seven invaded wetlands are as follow: Water temperature between 15.5 and 22.3 °C, pH between 7.1 and 8.6, dissolved oxygen as 3.7–8,8 mg l-1, electrical conductivity as 230–610 µS cm-1, salinity between 0.1 and 0.29 ppt, and ammonium as 0.25–0.74 mg l-1. The altitude range of the colonized wetlands is between sea level and 2100 m a.s.l. Elodea canadensis forms single species stands in many sites, but we could totally record 22 accompanying macrophyte taxa in species rich habitats. Here we present the most comprehensive distribution and ecology data for E. canadensis in Turkey which could be used for further research and management to understand its future spread and effect on native vegetation. [ABSTRACT FROM AUTHOR]

The invasive Asian date mussel Arcuatula senhousia has now been recorded from the Shatt Al-Basrah Canal in the south of Iraq. High densities of up to 102 ind.m-2 were found on rocky substrates in the intertidal zone during March 2020. The species was confirmed based on morphological characters of the shell. We hypothesize that the initial introduction was associated with shipping, with secondary dispersion into the Shatt Al-Basrah canal. It is possible that the species could extend its distribution into the Shatt Al-Arab and northern Arabian Gulf naturally or by additional anthropogenic means. [ABSTRACT FROM AUTHOR]

This Special Issue intended to collect articles focusing on the assessment of the possible effects of climate changes on aquatic species inhabiting inland waters all over the world, including the possible synergistic effects in combination with other anthropogenic stressors. A total of six original articles were published that report on investigations of different freshwater ecosystems across the world, including the mountain streams of the Western United States and Northwest Italy, river basins of Northwest China and Central Italy, a larger lowland river in north Italy, and a high-elevation temporary pond in Central Italy. In most of these papers, special attention was devoted to the repercussions of the climate change and its effects on three important components of the biotic community: the fish, benthic macroinvertebrates, and zooplankton. According to the aims of this Special Issue, three of the articles offer new insight into the synergistic effects of global warming together with other anthropogenic stressors, including water exploitation and alien species invasions. In light of the studies' aim to highlight the effects of climate change, three papers provided analyses of environmental data collected through long-term monitoring. The scientific findings provided by these studies could help to create sound management strategies for freshwater biodiversity conservation. [ABSTRACT FROM AUTHOR]

Suckermouth armored catfish (Pterygoplichthys disjunctivus) is one of the most widespread invasive species in Vietnam. However, it is relatively unknown how the species underwent its divergent adaptations to varying local conditions and habitat types, an understanding of which is essential for managing its invasion in Vietnam. We addressed this by analyzing a large number of fish (662 samples) collected in lotic (Dinh River) and lentic (Suoi Trau Reservoir) habitats in southern Vietnam during one year. The allometric growth patterns estimated by von Bertalanffy growth functions were Lt=4831−e−0.71(t−0.40) in Dinh River and Lt=3461−e−1.01(t−0.62) in Suoi Trau Reservoir. The estimated fish ages were 2.9 to 4.2 years old with an average total length from 206.10 ± 2.09 mm in Suoi Trau Reservoir to 319.22 ± 3.29 mm in Dinh River. The percentage of fish with matured ovaries peaked in August (100%) and was lowest in February (

We examined the association between habitat parameters and gastropod communities across a number of freshwater ecosystems, whose biodiversity has been affected by increased mining activities over decades. Reservoirs inhabited by the New Zealand mud snail (Potamopyrgus antipodarum (Gray, 1843)) exhibited different abiotic conditions than waterbodies that were not, such as higher salinity indicators (max. conductivity 13400 μS/cm, TDS 7700 mg/l and chlorides 7200 mg/l), and degraded water quality. In such water bodies P. antipodarum density was high (max. 23686/m2). Further, invaded waters were inhabited by less diverse gastropod communities than reservoirs without P. antipodarum. The invader has established reproducing populations and were the dominant species (D 87.53%), or formed mono-specific assemblages, in the reservoirs. Our results indicate that P. antipodarum occurred in habitats whose conditions are unfavorable or less preferred by other species, such as those with high conductivity, and high concentrations of chlorides and calcium. Since this snail is known to inhabit water bodies with degraded water quality, we assumed that along with the progressing development of industries worldwide, this species will continue to spread to industrial areas and will inhabit increasing numbers of anthropogenically affected water environments. Our study contributes to the global understanding of the mechanisms involved in successful establishment in waters by P. antipodarum, and is especially novel in addressing its occurrence in anthropogenically created ecosystems. Our results showed that human impact is the cause of the trend in P. antipodarum populations, and compared habitats from the perspective of both abiotic parameters and community structure. Human activities can have a significant impact on water quality that can result in the permanent establishment of P. antipodarum populations, especially when the environment is not favorable for the native species. [ABSTRACT FROM AUTHOR]

Citizen science is emerging as a powerful tool for the early detection of biological invasions. The exotic pet trade has been deemed as the most significant cause of establishment for reptiles, and among them, turtles have the highest number of introduction events. In Europe, at least 13 species of alien freshwater turtles have been recorded in the wild. In Greece, only two species of alien turtles have been reported, namely the American pond slider Trachemys scripta and the Florida cooter Pseudemys floridana. In this study, we provide an updated checklist of the alien freshwater turtles recorded in Greece, using citizen science, personal observations, and literature. Our results provide the first records for the country of five species, namely the Florida red-bellied cooter Pseudemys nelsoni, the Eastern river cooter Pseudemys concinna, the Chinese stripe-necked turtle Mauremys sinensis, the Chinese soft-shelled turtle Pelodiscus sinensis, and the Common snapping turtle Chelydra serpentina and new localities for T. scripta. Similar to the myth of the Lernaean Hydra (i.e., for every head chopped off, more would regrow), the pet turtle trade has been proven to have multiple heads.

Aquatic invasions are one of the major threats for freshwater ecosystems. However, in developing countries, knowledge of biological invasions, essential for the implementation of appropriate legislation, is often limited if not entirely lacking. In this regard, the identification of potentially invasive nonnative species by risk screening, followed by a full risk assessment of the species ranked as higher risk, enables decision-makers to be informed about the extent of the threats posed to the recipient (risk assessment) area. In this study, 32 non-native extant and horizon fish species were screened for their risk of invasiveness under current and predicted climate conditions for the South Caucasus - a biodiversity and geopolitical hotspot that includes the countries of Armenia, Azerbaijan and Georgia. Overall, the number of very high-risk species increased from four (12.5%) under current climate conditions to 12 (37.5%) under predicted climate conditions. The highest-risk species under both conditions included the already established gibel carp Carassius gibelio and topmouth gudgeon Pseudorasbora parva, the locally translocated pikeperch Sander lucioperca and the horizon North African catfish Clarias gariepinus. Under predicted climate conditions, a very high risk of invasiveness was predicted also for the translocated threespined stickleback Gasterosteus aculeatus and Eurasian perch Perca fluviatilis, for the already established eastern mosquitofish Gambusia holbrooki, ruffe Gymnocephalus cernua, sharpbelly Hemiculter leucisculus and Nile tilapia Orechromis niloticus, and for the horizon pumpkinseed Lepomis gibbosus and largemouth bass Micropterus salmoides. Future research on the non-native species in the South Caucasus should be conducted both country- and region-wide and should account not only for the high biodiversity, but also for the critical geopolitical situation affecting the study area. [ABSTRACT FROM AUTHOR]

The freshwater rotifer Kellicottia bostoniensis (Rousselet, 1908), native from North America, has been considered invasive in European, Russian and South American waterbodies. More than reporting its presence, for the first time, in Araguaia River, which plays critical role in a set of floodplain systems in the Brazilian savanna, we aim to understand how this invader react to new physical, chemical and hydrodynamics conditions, which can be helpful for predicting its invasiveness and colonization success in other similar non-native ranges. We use population data of K. bostoniensis and environmental variables surveyed across the meandering middle-stretch of the Araguaia River. The highest frequencies of K. bostoniensis were registered in sites of lower mean temperatures, higher pH and dissolved oxygen at sites with higher hydrodynamics. However, the highest abundance was found in a backwater site, a more lentic habitat in which total body size was slightly higher than those with lotic conditions. Both the abundance values and body length were the lowest registered in non-native areas, suggesting the initial phase of the invasion process. Also, the trade-off between abundance and body size may allow population to persist in flowing water conditions, thus playing fundamental role in population recruitment and dispersal, favoring the propagation of this organism in the river curse and adjacent environments. Specifically, stepping stones created by the river meanders would increase population growth and the rapid spread of K. bostoniensis through Araguaia River. Due to its wide environmental tolerance, morphological plasticity and high dispersal ability, we further anticipate continued dispersion of K. bostoniensis to other Brazilian basins highlighting the need for persistent monitoring upstream and downstream of this freshwater ecotone. [ABSTRACT FROM AUTHOR]

Dreissenid (zebra and quagga) mussels are spreading across North America and having an impact on freshwater ecosystems, through bottom-up impacts. Lakes in British Columbia are known to be at risk for mussel invasion due to favourable water chemistry and significant cross-border boat movements. This project uses Ecopath with Ecosim (EwE) to model a hypothetical mussel invasion into Shuswap Lake: one of the most popular lakes for recreation and one of the most productive sockeye lakes in the province. A model of the ecosystem was fit to available data and then projected forward to examine the effects from three different scenarios: no invasion, a base mussel invasion scenario resulting in a carrying capacity of 5 g∙m-2 and 15 g∙m-2 of zebra and quagga mussels, respectively, and a high density invasion scenario resulting in a combined carrying capacity of 40 g∙m-2 of Dreissenid mussels. The greatest ecosystem impacts resulted in declines in large piscivorous rainbow trout and lake trout, followed by non-anadromous kokanee salmon, with little effect observed on anadromous sockeye salmon. Two mechanisms limit the predicted impact of mussels in the study system: (1) paucity of shallow water habitat, limiting the scope for invasion; and (2) movements by fish in and out of the system. This second mechanism includes some resident species that rear for up to three years upstream of the lake, as well as anadromous species, which spend most of their life in the marine environment. While most of the effects are observed on recreationally important species, there is also the possibility of mussels spreading from this system into others within the same watershed, reiterating the importance of preventing the invasion and spread of Dreissenid mussels. [ABSTRACT FROM AUTHOR]

Broadleaf water milfoil ( Myriophyllum heterophyllum ) is an emerging invasive alien plant in Europe, and thus a priority for European Union (EU)-level surveillance, monitoring, and eradication. This species is native to North America and threatens aquatic ecosystems by creating dense stands that can fill an entire water body, leading to high economic costs and the loss of native biodiversity. Although its presence in Portugal is not reported, the species has already been established in several European countries, including neighboring Spain. In this study, we assessed the risk of invasion by this species in mainland Portugal by jointly considering environmentally suitable areas and the risk of human-mediated introduction. Environmental suitability was estimated using MaxEnt, which relates the known species distribution to climate, topography, and soil variables. The model achieved a mean area under the curve value of 0.96 ± 0.008 and identified the mean temperature of the warmest quarter as the most relevant variable for explaining the species distribution (67.2 %). Predictions from the model indicated that the peaks of suitability values were distributed mainly in temperate climate regions along central and northern coastal areas in Portugal. The risk of introduction was estimated by mapping and calculating the spatial density of the aquarium stores. Jointly considering environmental suitability and risk of introduction, we observed that hotspots at risk of invasion are concentrated on the Portuguese central and northern coasts and in the two main metropolitan areas, Lisbon and Porto. Several risk hotspots fall within protected areas and sites designated under the EU Habitats Directive, comprising water bodies of high significance for maintaining local vegetation and fauna. Therefore, it is necessary to take measures to reduce the risk of invasion by this species, namely, surveillance and monitoring efforts confirming its absence in the national territory and preventing its future arrival., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

This Special Issue intended to collect articles focusing on the assessment of the possible effects of climate changes on aquatic species inhabiting inland waters all over the world, including the possible synergistic effects in combination with other anthropogenic stressors. A total of six original articles were published that report on investigations of different freshwater ecosystems across the world, including the mountain streams of the Western United States and Northwest Italy, river basins of Northwest China and Central Italy, a larger lowland river in north Italy, and a high-elevation temporary pond in Central Italy. In most of these papers, special attention was devoted to the repercussions of the climate change and its effects on three important components of the biotic community: the fish, benthic macroinvertebrates, and zooplankton. According to the aims of this Special Issue, three of the articles offer new insight into the synergistic effects of global warming together with other anthropogenic stressors, including water exploitation and alien species invasions. In light of the studies’ aim to highlight the effects of climate change, three papers provided analyses of environmental data collected through long-term monitoring. The scientific findings provided by these studies could help to create sound management strategies for freshwater biodiversity conservation.

Infection of non-indigenous pumpkinseed (Lepomisgibbosus, Centrarchidae) with the bothriocephalidean cestode Bothriocephalusclaviceps (Cestoda: Bothriocephalidae) was confirmed at several sites in the lower Oder river basin in Poland. The preferred host for this cestode species is the European eel (Anguillaanguilla), with a wide range of other fish species serving as paratenic hosts. The pumpkinseed showed a relatively high prevalence and abundance of larvae, along with several mature and gravid specimens, thereby confirming development of B.claviceps to the adult stage in an alternative host. As such, the pumpkinseed may represent an additional definitive host for this cestode, in addition to its role as a paratenic host, as previously recorded in other European regions. Our results indicate that inclusion of pumpkinseed as an additional definitive host in the cestode's life cycle, high infection of pumpkinseed with B.claviceps larvae and inclusion of pumpkinseed in the eel's diet could potentially lead to increased parasite pressure on native fish hosts. Further comparative studies or experimental testing will be required to confirm this. [ABSTRACT FROM AUTHOR]

Desiccation resistance is a key trait determining the distribution of aquatic insects, their potential for overland dispersal, and survival during drought periods in temporary waterbodies, as well as the spread of invasive species. Passive dispersal by waterbirds is considered to be a key process favouring the spread of invasive species and is more likely to occur for insects with eggs that are resistant to desiccation or gut passage.We investigated the hypothesis that the eggs of the alien boatman Trichocorixa verticalis verticalis are resistant to desiccation and digestion and thus able to disperse via waterbirds.We conducted experiments to test for egg resistance to desiccation in still air and under moving air conditions, to simulate bird flight. Oviposition on greater flamingo (Phoenicopterus roseus) legs and wetland plants was tested in the laboratory and in the field. Resistance of eggs to simulated gut passage was studied, as was the viability of eggs recovered from Eurasian coot (Fulica atra) droppings in the field.Only a fraction of eggs hatched after 8 hr of exposure to still air at 15°C (4% of exposed eggs), and after 2 hr exposure to air flow conditions at 20°C (8%). Oviposition on flamingo legs was confirmed in the laboratory but not in the field. However, oviposition rates were higher on plant stems than on flamingo legs. Digestion simulations showed very low resistance to chemical treatment and no resistance to scarification, and eggs recovered from coot droppings did not hatch.Our experiments demonstrated that T. v. verticalis cannot be considered to have eggs resistant to desiccation or gut passage. However, the dispersal of eggs on legs of flamingos or other waterbirds may occur as rare events. This epizoochory of eggs could potentially contribute to the expansion and gene flow of T. v. verticalis around the Mediterranean region. [ABSTRACT FROM AUTHOR]

Aim: Ecological niche models (ENMs) are widely used to address urgent real‐world problems such as climate change effects or invasive species; however, the generality of models when projected through space and/or time, that is transferability, remains a key challenge. Here, we explored the effects of complex predictors and feature selection on ENM transferability in a widely employed algorithm, Maxent, using five globally invasive freshwater species as case studies. Location: Global. Methods: We modelled the global distributions of five notorious freshwater invasive species (African sharptooth catfish Clarias gariepinus, Mozambique tilapia Oreochromis mossambicus, American bullfrog Lithobates catesbeianus, red swamp crayfish Procambarus clarkii, and Australian redclaw crayfish Cherax quadricarinatus), using three predictor datasets of varying complexities derived from two commonly used climatic data sources (WorldClim and IPCC) and three methods of model tuning that differentially incorporated feature selection. Spatially explicit transferability assessments were then conducted using a suite of evaluation metrics previously used to quantify Maxent model performance. Results: We show that in the absence of detailed biological knowledge of focal species, simpler predictor datasets produce models that are more accurate than those calibrated using comprehensive "bioclimatic" datasets. Additionally, we find that tuning models for both optimal regularization parameters as well as feature‐class combinations led to the greatest increases in transferability and geographic niche conservatism. Results indicate a tenuous link between model transferability and Akaike's information criterion corrected for small sample sizes (AICc), suggesting that the indiscriminate use of AICc as an estimate of model parsimony may lead to erratic model performance. Main conclusions: Our findings demonstrate that methodological considerations can drastically affect the reliability of spatial and possibly temporal projections, which has severe implications when ENMs are used to infer species' niches, and quantify ecological or evolutionary change across impacted landscapes. [ABSTRACT FROM AUTHOR]

Dreissenid (zebra and quagga) mussels are spreading across North America and having an impact on freshwater ecosystems, through bottom-up impacts. Lakes in British Columbia are known to be at risk for mussel invasion due to favourable water chemistry and significant cross-border boat movements. This project uses Ecopath with Ecosim (EwE) to model a hypothetical mussel invasion into Shuswap Lake: one of the most popular lakes for recreation and one of the most productive sockeye lakes in the province. A model of the ecosystem was fit to available data and then projected forward to examine the effects from three different scenarios: no invasion, a base mussel invasion scenario resulting in a carrying capacity of 5 g·m-2 and 15 g·m-2 of zebra and quagga mussels, respectively, and a high density invasion scenario resulting in a combined carrying capacity of 40 g·m-2 of Dreissenid mussels. The greatest ecosystem impacts resulted in declines in large piscivorous rainbow trout and lake trout, followed by non-anadromous kokanee salmon, with little effect observed on anadromous sockeye salmon. Two mechanisms limit the predicted impact of mussels in the study system: (1) paucity of shallow water habitat, limiting the scope for invasion; and (2) movements by fish in and out of the system. This second mechanism includes some resident species that rear for up to three years upstream of the lake, as well as anadromous species, which spend most of their life in the marine environment. While most of the effects are observed on recreationally important species, there is also the possibility of mussels spreading from this system into others within the same watershed, reiterating the importance of preventing the invasion and spread of Dreissenid mussels. [ABSTRACT FROM AUTHOR]

Reducing the abundances of invasive species by removals aims to minimize their ecological impacts and enable ecosystem recovery. Removal methods are usually selective, modifying phenotypic traits in the managed populations. However, there is little empirical evidence of how removal‐driven changes in multiple phenotypic traits of surviving individuals of invasive species can affect ecosystem functioning and recovery. Overcoming this knowledge gap is highly relevant because individuals are the elemental units of ecological processes and so integrating individual‐level responses into the management of biological invasions could improve their efficiency. Here we provide novel demonstration that removals by trapping, angling and biocontrol from lakes of the globally invasive crayfish Procambarus clarkii induced substantial changes in multiple phenotypic traits. A mesocosm experiment then revealed that these changes in phenotypic traits constrain recovery of basic ecosystem functions (decomposition of organic matter, benthic primary production) by acting in the opposite direction than the effects of reduced invader abundance. However, only minor ecological impacts of invader abundance and phenotypic traits variation remained a year after its complete eradication. Our study provides quantitative evidence to an original idea that removal‐driven trait changes can dampen recovery of invaded ecosystems even when the abundance of invasive species is substantially reduced. We suggest that the phenotypic responses of invaders to the removal programme have strong effects on ecosystem recovery and should be considered within the management of biological invasions, particularly when complete eradication is not achievable. [ABSTRACT FROM AUTHOR]

The Puelo and Petrohué rivers were surveyed between April 2016 and February 2017 to assess the presence and seasonal abundance of Didymosphenia geminata in the wild aquatic systems of these two important rivers in southern Chile. Didymo was reported in the Puelo River in 2012, while it was declared absent from the Petrohué River before this study commenced in the fall of 2016. Results showed that cells of D. geminata were recorded in both rivers, in the Phytobenthos as well as in the water column. However, the classical mucilage which characterizes this plague was only recorded in one of the sampled rivers (Puelo). The mucilage was not recorded in any of the sections sampled in the Petrohué River, which was attributed to the high concentration of phosphorous present in the system. The concentration of phosphorous recorded throughout the study in the Puelo River was low. However, differences in the recorded presence or absence of D. geminata between sampling sites on the Petrohué River was mainly attributable to the availability of incident sunlight. This study records for the first time the presence of D. geminata in the Petrohué River. [ABSTRACT FROM AUTHOR]

• Invasive species as indicator and a tool of degraded aquatic systems. • Huge differences in invader density between aquatic systems under anthropopressure. • Identifying a group of environmental factors favoring P. antipodarum colonization. • Strong need to include its spread reduction in industrial areas worldwide in management priorities. • Control and reduction the number of created anthropogenic water bodies. Global changes in climate and human impact favour invasions of aquatic organisms. Along with habitat modification, the abundance of invasive species might increase, leading to their greater impact on ecosystems functioning in disturbed areas. The appearance of species, which are drivers for ecosystem pollution are useful tool for the indication of some environmental changes in the area. We examine the occurrence of P. antipodarum populations, a global invader that established rivers, oxbow lakes, dam reservoirs, sand pits, gravel pits, and subsidence ponds in Poland (Central Europe). The research aims were to determine the extent of invasion in anthropogenically impacted habitats and the relationship between the abundance of aquatic invertebrates and oxygen concentration, pH, N-NO2, N-NO3, chlorides, and ammonia. This investigation helps elucidate the potential of invader to adapt to adverse environmental conditions in aquatic systems in which it was found dominant. The abundance of P. antipodarum showed an unimodal distribution, being higher in disturbed conditions. In snail communities it was a supereudominant or eudominant species in rivers, gravel pits, sand pits and subsidence ponds. Its relative abundance was the highest in gravel pits, in which it constituted more than 50 percent of benthic fauna. We demonstrated that environmental disturbances and pollution increase the vulnerability of water biocoenoses to invasions and the origin of free niches and that P. antipodarum is an indicator of degraded water systems. Results support the management of aquatic systems colonized by invasive species and highlight the need to assess the level of pollution discharged to prevent their dispersion. Management priorities must include the reduction or halt of invader spread because new aquatic environments are and will be created in industrial areas of the world. [ABSTRACT FROM AUTHOR]

Biological invasions threaten biodiversity on a global scale, therefore, developing predictive methods to understand variation in ecological change conferred is essential. Trophic interaction strength underpins community dynamics, however, these interactions can be profoundly affected by abiotic context, such as substrate type. The red swamp crayfish (Procambarus clarkii) has successfully invaded a number of freshwater ecosystems. We experimentally derive the Functional Response (FR) (density dependent predation) of the red swamp crayfish preying upon both a benthic prey; chironomid larvae, and a pelagic prey; Daphnia magna, on a no substrate control, sand, and gravel substrates to determine whether (1) there is a higher impact on prey that are benthic, and (2) whether the presence of different substrate types can dampen the interaction strength. We apply and demonstrate the utility of the Functional Response Ratio (FRR) metric in unravelling differences in ecological impact not obvious from traditional FR curves. Procambarus clarkii is capable of constantly utilising high numbers of both benthic and pelagic prey items, showing a Type II functional response under all scenarios. The presence of gravel and sand substrate each independently decreased the magnitude FR upon D. magna. Though, with regards to chironomid larvae the FR curves showed no difference in magnitude FR, the FRR reveals that the highest impact is conferred when foraging on sand substrate. This reinforces the need for impact assessments to be contextually relevant. [ABSTRACT FROM AUTHOR]

Invasive African clawed frog Xenopus laevis (Daudin, 1802) are considered a major threat to aquatic environments. Beginning in the early 1970s, invasive populations have now been established throughout much of central Chile. Between September and December 2015, we studied a population of X. laevis from a small pond in Viña del Mar, where we estimated the population size and evaluated the use of hand nets as a method of control. First, by means of a non-linear extrapolation model using the data from a single capture session of 200 min, a population size of 1,182 post-metamorphic frogs (range: 1,168-1,195 [quadratic error]) and a density of 13.7 frogs/m2 (range: 13.6-13.9) of surface water were estimated. Second, based on 10 capture-and-removal sessions of 60-min and separated by approximately 2 weeks each, a total of 2,184 post-metamorphic frogs were removed, but the number of captured individuals did not significantly decrease over time. Additionally, using novel records of its occurrence, we updated the distribution range of X. laevis in Chile, estimated at 36,055 km2, which is 1.7 to 3.5 times higher than previously assessed. Our results indicate that invasive X. laevis can reach extremely high densities, and removal of individuals in large numbers was not useful in reducing its abundance. This study shows that control and eradication of X. laevis from invaded areas proves extremely difficult, particularly when populations are wellestablished and/or expanding, as occurs in Chile. Our study reports the first record of X. laevis invading rivers of north Chile, 380 km north of previously reported. A management plan is urgently needed to prevent its further spread, and subsequent impacts on biodiversity. We propose our model and methodology as a tool to estimate and compare X. laevis densities, while suggesting the need to explore other control techniques in order to identify cost-effective strategies to contain the spread of X. laevis into new areas. [ABSTRACT FROM AUTHOR]

The round goby, Neogobius melanostomus, is a Ponto-Caspian fish species currently found in many parts of Europe, including the North Sea riverine deltas. The objective of this study was to examine the parasite community of fish caught in the lower Elbe (Süderelbe – tidal zone; Geesthacht – non-tidal) in Germany and compare it with published data from the upper Elbe (Ústí nad Labem) in the Czech Republic. Twelve parasite taxa were recorded in the lower Elbe, six in the Süderelbe and nine near the city of Geesthacht. Süderelbe fish were mainly infected with Angullicola crassus larvae, while gobies from Geesthacht – with glochidia and sporadically occurring Pomporhynchus laevis, and the opposite situation was observed at Ústí nad Labem. It appears that a large tidal weir at Geesthacht significantly contributes to the division of the round goby population, with the Geesthacht parasite community being more similar to that at Ústí nad Labem than the one from the Süderelbe, thus increasing the likelihood that shipping from Hamburg was the introduction vector to Ústí nad Labem. We also recorded Acanthocephalus rhinensis in the Elbe for the first time, and in a new host – the round goby. Thus, round gobies may represent a new vector for the introduction of this parasite along the Elbe. [ABSTRACT FROM AUTHOR]

Recognizing common reporting patterns of aquatic invasive Zebra mussels ( Dreissena polymorpha , ZM) and Eurasian watermilfoil ( Myriophyllum spicatum , EWM) helps to better understand invasions. We hypothesize that confirmed invasions may be confounded by human population density, leading to overrepresentation of invasions in highly populated areas and underrepresentation in less populated areas. Here we recognize dispersal patterns of confirmed ZM and EWM invasions in Minnesota, USA, using spatial clustering and directionality tests, while adjusting for human density. By 2015, 125 (0.68%) and 304 (1.65%) of 18,411 Minnesota waterbodies were reported to have ZM and EWM, respectively. A multivariate multinomial model of the scan test was used to identify clustering of invasions. The resulting 23 clusters included 13 with either or both ZM and EWM, and most clusters (11/13) occurred in areas with >10 people per square kilometer. Whereas, among the 10 clusters without invasion, nine were from less populated areas. The standard deviation ellipse and the spatiotemporal directionality tests indicated a northwestern trend of invasions, which is in the same direction as the I-94 interstate highway connecting urban centers. Results suggested that confirmed ZM and EWM invasions are potentially confounded by human densities, which is explained by varying human impact on either or both dispersal and reporting of invasions. Considering this impact of human density, we suggest that a combination of passive and targeted surveillance, where the magnitude of efforts are stratified by the human densities, may provide insight into the true invasion status and its progression in the Great Lakes region. [ABSTRACT FROM AUTHOR]

Biological invasions are a global environmental problem. They have resulted in enormous ecological and economic consequences worldwide, and they are among the greatest threats to biodiversity and ecosystem function. Spartina alterniflora, an invasive plant, has caused great ecological influence since it was introduced to China over 30 years ago. According to supervised classification and visual interpretation of three remote-sensing images (2002, 2006 and 2010), we attained the spatial population distribution of S. alterniflora in Xiangshan Bay, Ningbo, Zhejiang province. To explore the topic further, dynamic change processes were also analyzed using the IDRISI software and their spatial distributions in 2010 and 2014 predicted using a CA-Markov model. It was found that compared with remote-sensing image interpretation maps in 2010 and 2013, accuracy verification yielded overall Kappa coefficients of 81.99% and 85.57% respectively, indicating a good predictive result from the CA-Markov model. Therefore, the model can be used for long-term forecasting such as determining the dynamic change processes and evolution trends of S. alterniflora in the Xiangshan area over the next 20 years. This can in turn provide guidance for effective management and control of invasive plant populations such as S. alterniflora. [ABSTRACT FROM AUTHOR]

The rate of aquatic invasions by planktonic organisms has increased considerably in recent decades. In order to effectively direct funding and resources to control the spread of such invasions, a methodological framework for identifying high-risk transport vectors, as well as ruling out vectors of lesser concern will be necessary. A number of estuarine ecosystems on the North American Pacific Northwest coast have experienced a series of high impact planktonic invasions that have slowly unfolded across the region in recent decades, most notably, that of the planktonic copepod crustacean Pseudodiaptomus inopinus. Although introduction of P. inopinus to the United States almost certainly occurred through the discharge of ballast water from commercial vessels originating in Asia (the species’ native range), the mechanisms and patterns of subsequent spread remain unknown. In order to elucidate the migration events shaping this invasion, we sampled the genomes of copepods from seven invasive and two native populations using restriction-site associated DNA sequencing. This genetic data was evaluated against spatially-explicit genetic simulation models to evaluate competing scenarios of invasion spread. Our results indicate that invasive populations of P. inopinus exhibit a geographically unstructured genetic composition, likely arising from infrequent and large migration events. This pattern of genetic patchiness was unexpected given the linear geographic structure of the sampled populations, and strongly contrasts with the clear invasion corridors observed in many aquatic systems. [ABSTRACT FROM AUTHOR]

Abstract: The vast majority of global freshwater ecosystems are small lakes with less than 100 m2 surface area. These lakes are often unconnected to other water bodies but frequently host fish populations. Existing explanations for how fish colonize such remote habitats often involve birds as vectors transporting fish eggs as propagules. In this study, we aim to quantify the prevalence of these explanations among relevant societal groups as well as their scientific knowledge basis. We analyzed entries in online blogs and forums and surveyed the opinions of local stakeholders and decision makers using a questionnaire. To collect published scientific knowledge, we conducted a structured literature review. Our results reveal a discrepancy between commonly found beliefs and the empirical knowledge supporting those beliefs: Dispersal of fish eggs by water birds was overall the most frequent explanation online and in the questionnaire. In the scientific literature, however, we found hardly any empirical research on passive fish egg dispersal. We propose research directions for how to close this gap of knowledge and suggest that future empirical studies on passive fish egg dispersal may be inspired by existing work on passive dispersal in aquatic invertebrates. Mitigating the belief‐evidence discrepancy on fish dispersal will be essential to better understand the patterns of fish biodiversity across landscapes, to counteract its losses, and inform management strategies for invasive fish species. [ABSTRACT FROM AUTHOR]

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There is a risk of ‘ecological surprises’ if multiple potentially interacting stressors are managed individually, which is a question attracting significant current interest. Habitat degradation and species introductions are major threats to global biodiversity, and riverine fish are among the most threatened taxa in the world. Our interest was whether the presence of non-native species can affect native fish sensitivity to water quality deterioration in a large region in northeastern Spain (99,700 km 2 , 15 catchments, 530 sites). We used a ‘base model’ with geographical and hydro-morphological variables, which are the major shaping factors in rivers. We tested whether water pollution, non-native species, or their interaction provided an improved understanding of patterns of distributions and health measurements of the twelve most common native species. There was little evidence that variation in native species abundance, where they occurred, the presence of diseases and changes in mean fish length or body condition was affected by water deterioration, the presence of non-native species, or their interaction. The disease rate and occurrence of native species might be affected, to a minor degree, by water quality changes and the presence of non-native species. Environmental conditions between sites with and without non-native fish differed in the condition of riparian areas and in water quality. Based on presence-absence data and changes in abundances through weighted average equations we also derived potential safe levels of salinization, nutrient pollution, and pH for the native fish. Overall, additive effects of stressors prevail over interactions, and the restoration of natural hydro-morphology in rivers is likely to be the most effective management approach to improving the prospects for the native fish fauna. [ABSTRACT FROM AUTHOR]

Two North American species of mosquitofish, the Western (Gambusia affinis Baird and Girard, 1853) and Eastern mosquitofish (G. holbrooki Girard, 1859), rank amongst the most invasive freshwater fishes worldwide. While the existing literature suggests that G. affinis was introduced to mainland China, empirical evidence supporting this assumption was limited, and the possibility remained that both species were introduced during campaigns attempting to reduce vectors of malaria and dengue fever. We used combined molecular information (based on phylogenetic analyses of sequence variation of the mitochondrial cytochrome b gene) and morphometric data (dorsal and anal fin ray counts) to confirm the presence of only one species, G. affinis, across ten sampling sites in mainland China. [ABSTRACT FROM AUTHOR]

We document the distribution of Didymosphenia geminata in central-southern Chilean rivers and identify the chemical and physical factors associated with its presence/absence (p/a). Repeated surveys in five successive years provided evidence that D. geminata could be nearing a biogeographic equilibrium in the region. D. geminata databases from extensive biological and environmental surveys in 187 rivers, within ten catchments, south of 38°S commenced in November 2010 and ran through May 2013. In addition, data from two other field surveys were used. The sites evenly distributed latitudinally were climatically characterized. The recent sampling program, following a published species distribution model, was designed to explore D. geminata distribution within thirteen catchments (34°S–48°S). An extensive river survey in 2014 (spring-summer) and in 2015 (autumn) included the p/a, and relative abundance of D. geminata cells in phytobenthos and in the drift. These p/a results showed that the probability of re -encountering D. geminata cells at sites where the species was previously found was significantly high while the probability of finding D. geminata cells at sites previously without the species was significantly low. This suggests that the distribution of D. geminata cells among suitable habitats was nearing completion. The relative abundance of D. geminata cells in the phytobenthos versus in the drift indicates seasonality with higher proportion of cells in the phytobenthos during the spring-summer than during the autumn. During the final surveys, principal component analysis of chemical and physical characteristics of rivers showed significant differences between rivers with and without D. geminata . Based on our observations of the distribution of D. geminata cells among rivers with suitable habitat conditions and the fluctuating rate of spread between rivers, we conclude that D. geminata is probably in the ending stage of its spatial demographic expansion in Chile surmounting the different barriers of the invasive process. [ABSTRACT FROM AUTHOR]

Dinoflagellates of the genus Ceratium are predominantly found in marine environments, with a few species in inland waters. Over the last decades, the freshwater species Ceratium hirundinella and Ceratium furcoides have colonized and invaded several South American basins. The purpose of this study was to create a distribution model for the invasive dinoflagellate C. furcoides in South America in order to further investigate the basins at potential risk, as well as the environmental conditions that influence its expansion. This species is known to develop blooms due to its mobility, resistance to sedimentation, and optimized use of resources. Although nontoxic, blooms of the species cause many problems to both the natural ecosystems and water users. Potential distribution was predicted by using a maximum entropy algorithm (MaxEnt). Model was run with 101 occurrences obtained from the scientific literature, and climatic, hydrological and topographic variables. The developed model had a very good performance for the study area. The most susceptible areas identified were mainly concentrated in the basins between southeastern Brazil and northeastern Argentina. Besides already affected regions, new potentially suitable areas were identified in temperate regions of South America. The information generated here will be useful for authorities responsible for water and watershed management to monitor the spread of this species and address problems related to its establishment in new environments. [ABSTRACT FROM AUTHOR]

A diverse array of molecular markers and constantly evolving analytical approaches have been employed to reconstruct the invasion histories of the most notorious invasions. Detailed information on the source(s) of introduction, invasion route, type of vectors, number of independent introductions and pathways of secondary spread has been corroborated for a large number of biological invasions. In this review, I present the promises and limitations of current techniques while discussing future directions. Broad phylogeographic surveys of native and introduced populations have traced back invasion routes with surprising precision. These approaches often further clarify species boundaries and reveal complex patterns of genetic relationships with noninvasive relatives. Moreover, fine-scale analyses of population genetics or genomics allow deep inferences on the colonization dynamics across invaded ranges and can reveal the extent of gene flow among populations across various geographical scales, major demographic events such as genetic bottlenecks as well as other important evolutionary events such as hybridization with native taxa, inbreeding and selective sweeps. Genetic data have been often corroborated successfully with historical, geographical and ecological data to enable a comprehensive reconstruction of the invasion process. The advent of next-generation sequencing, along with the availability of extensive databases of repository sequences generated by barcoding projects opens the opportunity to broadly monitor biodiversity, to identify early invasions and to quantify failed invasions that would otherwise remain inconspicuous to the human eye. [ABSTRACT FROM AUTHOR]

Aquatic invasive species are a major threat to native freshwater ecosystems and cause enormous ecological and economic damage worldwide. Didymosphenia geminata (Lyngbye) M. Schmidt is an emerging invasive aquatic species that is spreading aggressively in Southern South America. Using niche analysis and species distribution models (SDMs), we examined niche requirements of D. geminata using climatic, topographic, and biological variables. We compared the realized niche of the species in the United States (US) with the niche in Chile. Within Chile, we also examined the environmental conditions (environmental envelopes) of rivers with and without this alga, to assess whether this species has the potential to colonize more rivers. Finally, we compared the SDMs from the US and Chile projected to Chile. Results showed that the potential distribution of D. geminata varied significantly between US and Chile. The US-based model predicted a geographic distribution in Chile which ranged from 32° to 55° S latitude while the Chile-based model predicted suitable habitats only from 36° to 48° S, and not so in the coastal ranges nor in Southern Patagonia (~ 52-55°S). In Chile, we found no differences in the environmental envelopes of the invaded and uninvaded rivers, thus suggesting that this species has even more suitable habitats to invade. These results can be used for prioritizing survey sites in Southern Chile for an early detection and management of D. geminata and for the conservation of native flora and fauna in freshwater ecosystems in Chile. [ABSTRACT FROM AUTHOR]

The socio-economic impacts of the free-floating aquatic plant water hyacinth, Eichhornia crassipes (Pontederiaceae), on aquatic systems are well documented, yet the impacts on aquatic biodiversity, particularly invertebrate biodiversity, are less well understood. This study aimed to determine whether the presence of water hyacinth altered the diversity and assemblage structure of benthic macroinvertebrates in a conservation area. The benthic macroinvertebrate assemblage was sampled over 1 year at five sites under water hyacinth mats and at five sites without water hyacinth at Lake Nsezi-Nseleni River in the vicinity of Richards Bay, KwaZulu-Natal, South Africa. Artificial substrates were placed beneath water hyacinth mats or in the open water to allow for colonization by freshwater macroinvertebrates, and left for a period of 6 weeks, repeated on seven occasions. Twenty nine families comprising 18,797 individuals were collected, 817 (13 families) individuals were from under water hyacinth mat sites compared to 17,980 (27 families) individuals from open water sites. Ninety-eight percent of individuals collected were, however, the invasive snail, Tarebia granifera. Open water samples were separated from samples beneath the water hyacinth mat by non-metric Multidimensional Scaling, indicating reduced biodiversity associated with the presence of water hyacinth. Exclusion of the dominant Thiaridae from the analysis did not alter the groupings. Family richness(s) and abundance ( N) were significantly higher in open water communities(S: H = 21.09; P = 0.0001; N: H = 22.58; P = 0.00001), while evenness ( J') was higher under water hyacinth mats (H = 20.13; P = 0.0002). The presence of water hyacinth had a significantly negative impact on aquatic macroinvertebrate biodiversity in a conservation area, and therefore the control of this invasive aquatic plant must play a major role in catchment management. [ABSTRACT FROM AUTHOR]

Paracaprella pusilla Mayer (Fauna und Flora des Golfes von Neapel 17:1–55, 1890 ), originally described from Brazil, is one of the most abundant caprellid amphipod species in tropical and subtropical seas around the world. During a survey of caprellid amphipods from marinas along the Balearic Island (Western Mediterranean Sea) carried out between November 2011 and August 2012, we found two established populations of P. pusilla in Mallorca and Ibiza, respectively. So far, its occurrence in European waters was reported only from southwestern Spain in 2010. This record represents a northward range expansion of the species’ distribution, which is found for the first time in the Mediterranean. This is also the first record of the genus Paracaprella in the Mediterranean Sea. The most probable introduction vector was ship fouling. We also found the invasive caprellid Caprella scaura Templeton (Trans Entomol Soc Lond 1:185–198, 1836 ) in Mallorca and Menorca, which is recorded for the first time in the Balearic Islands, confirming its rapid expansion along the Mediterranean. When comparing reproductive traits between both alien species, we found that P. pusilla has a higher fecundity than C. scaura for the same female size. Taking into account this evidence, the species may be expected to appear in other Mediterranean and adjacent areas. [ABSTRACT FROM AUTHOR]

Although exotic species of Ostracoda have been recorded from various sites in Europe, none of them have a widespread European distribution. Reviews of existing literature, examination of specimens, and sampling in Spain and Japan has greatly expanded the known distribution of the candonid ostracode Fabaeformiscandona subacuta (Yang, 1982). We herein present new reports of its presence in mainland eastern Asia, Australia, and South America, and we review its distribution on the Iberian Peninsula. Although this species is globally widespread, we hypothesize that it is an invasive species on the Iberian Peninsula in light of the following facts: it is not known from other European countries, its known global distribution is extremely disjunct, it has not been found during palaeo-limnological investigations of European lakes, and on the Iberian Peninsula it is almost exclusively found in artificial, intensely human-impacted habitats, mostly in reservoirs and ricefields. [ABSTRACT FROM AUTHOR]

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We built a family of hierarchical risk models for the spread of invasions by the spiny waterflea ( Bythotrephes longimanus) in lakes in Ontario, Canada. Knowledge of covariates determining lake invasibility and ability to predict risk of future invasions may help to develop management policy and slow the invasions in the future. The models are based on two component submodels. The first component was a stochastic gravity submodel for the propagule pressure between lakes via recreational boaters. The second component was a submodel for establishment risk, given that the invader has already been introduced to a lake. This component was a logistic regression model, incorporating up to 17 measured covariates that describe the physical and chemical condition of the lake. Variants of the risk model, each incorporating different subsets of the covariates, were calibrated using presence/absence data from a 300-lake survey conducted in 2005-2006 by the Canadian Aquatic Invasive Species Network (CAISN). The predictive capacity of the best model was high, giving AUC values close to 0.94. Of the model covariates considered, the most important predictors of existing invasions were propagule pressure and lake pH, and, to lesser extents, phosphorus (P) and lake elevation. Our fitting of the propagule pressure submodel demonstrated a significant Allee effect for Bythotrephes. Our development of the establishment risk predictor showed that it is essential to account for temporal variability in lake physico-chemistry. We demonstrated that invasions of lake networks by the spiny waterflea follow highly predictable patterns which can be understood with a properly calibrated, hierarchical risk model. [ABSTRACT FROM AUTHOR]

Aquatic plant invasions are often associated with long-distance dispersal of vegetative propagules and prolific clonal reproduction. These reproductive features combined with genetic bottlenecks have the potential to severely limit genetic diversity in invasive populations. To investigate this question we conducted a global scale population genetic survey using amplified fragment length polymorphism markers of the world’s most successful aquatic plant invader – Eichhornia crassipes (water hyacinth). We sampled 1140 ramets from 54 populations from the native (South America) and introduced range (Asia, Africa, Europe, North America, Central America and the Caribbean). Although we detected 49 clones, introduced populations exhibited very low genetic diversity and little differentiation compared with those from the native range, and ∼80% of introduced populations were composed of a single clone. A widespread clone (‘W’) detected in two Peruvian populations accounted for 70.9% of the individuals sampled and dominated in 74.5% of the introduced populations. However, samples from Bangladesh and Indonesia were composed of different genotypes, implicating multiple introductions to the introduced range. Nine of 47 introduced populations contained clonal diversity suggesting that sexual recruitment occurs in some invasive sites where environmental conditions favour seedling establishment. The global patterns of genetic diversity in E. crassipes likely result from severe genetic bottlenecks during colonization and prolific clonal propagation. The prevalence of the ‘W’ genotype throughout the invasive range may be explained by stochastic sampling, or possibly because of pre-adaptation of the ‘W’ genotype to tolerate low temperatures. [ABSTRACT FROM AUTHOR]