This review examines the ecological, economical, and public health significance of chironomids and provides examples of chironomid invasions via international shipping and the subsequent local and regional impacts. Dispersal and adaptation mechanisms as facilitators of chironomid invasions are presented, and control methods are discussed. Impacts ranged from increased nuisance occurrences to agricultural disruption. Anthropogenic activities including pollution-related decimation of aquatic benthic communities might allow introduction of invasive chironomids. Chironomids can inhabit many environments, including eutrophic lakes and wastewater treatment areas, and may accumulate contaminants in high concentrations. Health concerns include the association of chironomid egg masses with Vibrio cholerae, roles of chironomids as vectors for avian botulism, and effects of chironomid chemicals as human allergens. Therefore, the presence of new chironomid species in an environment may present threats to public health and local ecosystems.

Unravelling how a multiplicity of global change factors might influence the expansion of alien plants is a major goal of invasion biology. We explored the association of climatic conditions (i.e. annual rainfall and average minimum temperature during the coldest months) and water quality (orthophosphate, nitrate concentrations and electrical conductivity), with blooms of the invasive fern Azolla filiculoides Lam. in the Doñana marshland (SW Spain), one of the most extensive wetlands in Europe. Azolla was first detected in Doñana in 2001. Its annual cover has been quantified since then through remote sensing. In the last decade there has been a considerable increase of orthophosphate and yearly fluctuations of nitrate. The first orthophosphate increase coincided with the presence of Azolla in Doñana. Since then, there has been a positive relationship between inter-annual variation in Azolla cover and minimum temperature during the coldest months. Our study shows that the Doñana marshland is facing rapid eutrophication and invasion by Azolla, most notably in years with high temperatures during the winter.

The Asian copepod Pseudodiaptomus forbesi has recently become established in the Columbia River. However, little is known about its ecology and effects on invaded ecosystems. We undertook a 2-year (July 2009 to June 2011) field study of the mesozooplankton in four reservoirs in the Columbia and Snake Rivers, with emphasis on the relation of the seasonal variation in distribution and abundance of P. forbesi to environmental variables. Pseudodiaptomus forbesi was abundant in three reservoirs; the zooplankton community of the fourth reservoir contained no known non-indigenous taxa. The composition and seasonal succession of zooplankton were similar in the three invaded reservoirs: a bloom of rotifers occurred in spring, native cyclopoid and cladoceran species peaked in abundance in summer, and P. forbesi was most abundant in late summer and autumn. In the uninvaded reservoir, total zooplankton abundance was very low year-round. Multivariate ordination indicated that temperature and dissolved oxygen were strongly associated with zooplankton community structure, with P. forbesi appearing to exhibit a single generation per year. The broad distribution and high abundance of P. forbesi in the Columbia–Snake River System could result in ecosystem level effects in areas intensively managed to improve conditions for salmon and other commercially and culturally important fish species.

Rapid range expansion is one of the major attributes of invasion success. During range expansion, dispersing individuals face a novel environment where trade-offs between benefits of reduced conspecific density and pressure from niche competitors may differentially affect life-history traits essential for population growth. In this study, we examined differences in sex ratio, body condition, physiological condition and capacity for energetic investment into reproduction along an actively expanding range of one of the most successful crayfish invaders in Europe, the signal crayfish (Pacifastacus leniusculus). In the examined invasive range, signal crayfish faces competition by a native crayfish, Astacus leptodactylus. By comparing measured parameters between invasion fronts and invasion core sites, we analyzed whether the potential benefits of dispersal to areas with low conspecific density are outweighed by the competitive pressure from a native crayfish. Caught signal crayfish of both sexes from invasion fronts were in a better body condition compared to those from the invasion core, while females from invasion fronts also exhibited better energetic status of hepatopancreas and gonads. At the same time, A. leptodactylus from the contact zones at invasion fronts were in poorer body condition compared to those outside the invaded range. Thus, interspecific competition at invasion fronts affected the native A. leptodactylus more strongly than the signal crayfish, which still benefited from the reduced conspecific density in the presence of a competitor. This study highlights the importance of examining trait variability as invader advances its range, since a shift between the rate of population growth and counteracting pressure from other niche competitors could represent one of the crucial determinants of a lag between establishment and expansion of invasive species.

Along the French coast of the English Channel, Hemigrapsus sanguineus (De Haan, 1835) is abundant under boulders on exposed shores that have high-energy hydrodynamic conditions in the intertidal zone. However, small individuals (< 6 mm) are rare in the muddy gravel sediments under boulders and the settlement habitat for post-larvae is largely unknown. This study explored whether mussel beds could represent a settlement zone for H. sanguineus. At the end of the summer of 2013, there were many post-larvae and small crabs in some mussel beds, with up to 528 individuals/m². However, at one location, no juveniles of H. sanguineus were found in mussel bed habitat despite the presence of adults on the same shore. We conclude that mussel beds are an important habitat for the settlement of juvenile crabs.

The western tubenose goby (Proterorhinus semilunaris) is one of several Ponto-Caspian gobiid species currently extending their distribution range over Europe. As part of an ongoing study, we examined the annual dynamics of an established tubenose goby population from the River Dyje (Czech Republic, Danube basin), 13 years after its first occurrence. Monthly monitoring (February 2011-January 2012) confirmed that the species dominates the local fish assemblage (more than two thirds of fish caught) and is the only species captured every month. The population is female-dominated from March-August and displays a 1:1 sex-ratio from September on. Tubenose gobies in the Dyje are characterised by rapid reproduction and early maturation, with all 0+ fish ready to spawn at the start of the next spawning season. Females display significantly higher GSI but lower body condition and a shorter life-span than males. Female life-span was almost strictly annual, while males were more likely to survive to a second spawning season. This study is unique in presenting results for a tubenose goby population with long-term absence of other potentially competing gobiid species. These results provide new baseline data for future tubenose goby studies in areas both with and without competitors.

The American bullfrog (Lithobates catesbeianus) is a globally distributed invasive species that was introduced to the Yellowstone River floodplain of Montana. Knowledge about floodplain habitat features that allow for bullfrog persistence and spread will help identify effective control strategies. We used field surveys in 2010, 2012 and 2013 to describe bullfrog spread in the Yellowstone River floodplain and the habitat features that are associated with bullfrog occupancy and colonization. Bullfrogs in our study area expanded from ~ 60 km in 2010 to 106 km in 2013, and are spreading to up- and downstream habitats. The number of breeding sites (i.e., presence of bullfrog eggs or larvae) increased from 12 sites in 2010 to 45 sites in 2013. We found that bullfrogs were associated with deeper waters, emergent vegetation and public-access sites, which are habitat features that characterize permanent waters and describe human-mediated introductions. Control strategies that reduce the hydroperiod of breeding sites may help to limit bullfrog persistence and spread, while an increase in public outreach and education may help prevent further bullfrog introductions at public-access sites.

The red-eared slider turtle, Trachemys scripta elegans, is among the most over-exploited animals and is still exported annually from the USA all over the world. Once introduced into its new environment, feral populations may arise and pose threats to local biodiversity and ecosystem functioning. In France, it is in fact considered as a risk for the Mediterranean pond turtle, Mauremys leprosa, and the European pond turtle, Emys orbicularis, as they may compete for resources and habitat. Freshwater turtles are also host to a variety of parasites including protozoans and helminths. When introduced turtles escape, parasites may spread to native species. The objective of this study was to document the extent of platyhelminth invasions from T. s. elegans to natural M. leprosa populations in northern Spain and southern France and to evaluate the risks that parasite host-switching may pose on indigenous freshwater turtle species. From DNA barcoding analysis based on the sequencing of the Cytochrome c Oxidase I gene, the Bayesian tree and p-distance comparisons of closely related haplotypes revealed a greater polystome richness within M. leprosa than expected, suggesting that host switching may take place in natural environments. Because these parasites most typically infest American turtles like Chrysemys picta marginata and Graptemys pseudogeographica in their natural home range and because parasites were also found within T. s. elegans feral populations, it is suggested that the red-eared slider would serve as a carrier for a variety of not strictly host-specific polystomes that are transmitted to M. leprosa throughout the south of France. The global trade in freshwater turtles thus provides opportunity for parasites to be transported to new destinations which could impact the physiology, behavior and survival of native turtle species.

Herein we provide first genetic evidence that Dreissena bugensis Andrusov, 1897 has reached the German Danube system. The occurrence of this species at several sampling sites along a 152 km river stretch of the upper Danube River thereby proved to be wrongly estimated by using solely shell morphology features for species identification. 17.5% of the dreissenid specimens (Dreissena bugensis, N=26, Dreissena polymorpha, N=34), identified according to exterior shell characteristics, were assigned to the wrong species. In contrast to RFLP identification, comparisons of shell dimension measurements by discriminant function analysis were not able to fully identify the two species, with correct classification rates between 61.1% and 94.4%, confirming their high morphological plasticity. The results of this study suggest that species records of dreissenid mussels should generally be genetically verified.

Specimens of Abudefduf sp. collected in the Levantine region were previously assumed to be the Lessepsian-immigrant Indo-Pacific sergeant Abudefduf vaigiensis (Quoy and Gaimard, 1825). Using phylogenetic analysis of mitochondrial genes cytochrome c oxidase I (COI) and 16S rRNA probed in 10 individuals sampled in the Mediterranean Israel and on 10 individuals sampled in the Red Sea, we established that Atlantic-origin sergeant major Abudefduf saxatilis (Linnaeus, 1758) now occurs along the eastern Mediterranean in shallow coastal rocky habitats. This study showed that misidentifications resulting from phenotypic plasticity and conservative morphological analysis may lead to wrong conclusions regarding the biogeography of studied species. In this respect, molecular tools are necessary to rule between the Lessepsian and Atlantic origin of non-indigenous cryptic species.

In this study, we compiled existing records of fouling marine non-native species in Scotland, and created a national checklist of these species. We then targeted a selection of these species (excluding those that could not be reliably identified) in a rapid assessment survey of 27 harbours in the north of Scotland. Collation of existing records revealed that 23 fouling marine non-native species were known to be present in Scotland. The geographic distribution of these records was not uniform, and they were largely underrepresented in the north and east of mainland Scotland, likely as result of lack of survey effort. In the rapid assessment survey of north Scotland, 9 out of 18 targeted species were found: Austrominius modestus (Darwin, 1854); Botrylloides violaceus Oka, 1927; Caprella mutica Schurin, 1935; Codium fragile fragile (Suringar) Hariot, 1889; Corella eumyota Traustedt, 1882; Heterosiphonia japonica Yendo, 1920; Neosiphonia harveyi (Bailey) Kim, Choi, Guiry and Saunders, 2001; Schizoporella japonica Ortmann, 1890; and Tricellaria inopinata d'Hondt and Occhipinti Ambrogi, 1985. The non-native bryozoan Bugula simplex Hincks, 1886, which was not targeted, was also found, and this constituted the first confirmed Scottish record. The surveys provided 60 new records and extended the northward national range for most of the species found. The number of fouling non-native species in the surveyed harbours was positively associated with the presence of floating structures and vessel activity indices. Our study presents an overview of the current status of fouling marine non-native species in Scotland, and the results of the first comprehensive survey of these species in the north of Scotland. The latter provides a baseline dataset for monitoring future changes, which may occur as a result of the development of the wave and tidal energy industry in the north of Scotland. The wave and tidal energy industry has the potential to facilitate the invasion of fouling marine non-native species through the provision of habitat and by increasing vector activity.