In the Laurentian Great Lakes, the invasive form of Phragmites australis (common reed) poses a threat to highly productive coastal wetlands and shorelines by forming impenetrable stands that outcompete native plants. Large, dominant stands can derail efforts to restore wetland ecosystems degraded by other stressors. To be proactive, landscape-level management of Phragmites requires information on the current spatial distribution of the species and a characterization of areas suitable for future colonization. Using a recent basin-scale map of this invasive plant’s distribution in the U.S. coastal zone of the Great Lakes, environmental data (e.g., soils, nutrients, disturbance, climate, topography), and climate predictions, we performed analyses of current and predicted suitable coastal habitat using boosted regression trees, a type of species distribution modeling. We also investigated differential influences of environmental variables in the upper lakes (Lakes Superior, Michigan, and Huron) and lower lakes (Lakes St. Clair, Erie, and Ontario). Basin-wide results showed that the coastal areas most vulnerable to Phragmites expansion were in close proximity to developed lands and had minimal topographic relief, poorly drained soils, and dense road networks. Elevated nutrients and proximity to agriculture also influenced the distribution of Phragmites. Climate predictions indicated an increase in suitable habitat in coastal Lakes Huron and Michigan in particular. The results of this study, combined with a publicly available online decision support tool, will enable resource managers and restoration practitioners to target and prioritize Phragmites control efforts in the Great Lakes coastal zone.

Recent records of the invasive ctenophore Mnemiopis leidyi A. Agassiz, 1865 in the North Sea are a cause for concern due to the detrimental effects this invader has had on fish stocks in the Black and Caspian seas. The North Sea is a major fishing ground and has spawning and nursery areas for many important fish species. These may be affected by competition and predation from Mnemiopsis leidyi, so it is important to determine whether the species, having been introduced, is likely to become established and produce blooms. This study applies temperature, salinity, and food constraints to data from the GETM-ERSEM-BFM model to evaluate the suitability of the North Sea for survival and reproduction of this invasive species. Large parts of the North Sea were found to be suitable for Mnemiopsis leidyi reproduction in summer months, although in most areas the suitable time window would not allow completion of more than two life cycles. The highest risk areas were in southern coastal and estuarine regions and in the Skagerrak and Kattegat, due to a combination of high temperatures and high food concentrations. Importantly, food was found to limit winter survival and so may restrict the overwintering population. Continued monitoring of this species, especially in areas predicted to be at a high risk, will be essential to determine whether it is likely to become a problem in the North Sea.

We investigated the abundance, trophic position, and linkages to basal energy sources of the non-indigenous prawn Palaemon elegans in shallow (0.5–1.6 m) stony habitats of the exposed coast of the SE Baltic Sea. Prawn abundance at the site with artificial stone was higher than that in the natural stony habitats. Stable isotope analysis (SIA) suggested similarity in feeding between different size classes of P. elegans. However, SIA of stomach contents showed greater variability of ingested food among large individuals (body length > 25 mm). Trophic position was estimated at 3.0 ± 0.8 suggesting the prevalence of animal prey in the assimilated diet of P. elegans. However, filamentous green algae was also consumed by large-sized individuals, as indicated by their isotopic signature and the elemental (C:N) ratio of their stomach contents. Modeling of the contribution of Cladophora and particulate organic matter, as basal food sources, to the diet of P. elegans (two end-member mixing model) revealed that only 40% of the assimilated biomass was derived from macroalgae, either directly or through intermediate consumers. This finding suggests that pelagic production was the main carbon source supporting prawn’s nutrition. In an experimental study, P. elegans readily consumed mysids, suggesting that this prey may be the prawn’s link to the pelagic food chain.

This paper represents the first attempt to study the microfungal flora contained in the digestive system of the most widespread aquatic invasive invertebrate in the world: Procambarus clarkii (Cambaridae, Decapoda). Understanding its bioinvasion, in terms of ecological risk and environmental impact, requires a multidisciplinary approach that considers consequences on all levels, from macroscopic to microscopic. In this study, we investigated both the population dynamics and the dietary habits of the red swamp crayfish captured within a natural biotope in Northern Italy. The diet was mainly based on plant detritus. The analysis of microfungal flora in the crayfish stomach revealed a fairly constant composition, unrelated to season and diet. Since most of the fungi were associated with detritus and some species were particularly frequent, we formulate the hypothesis that the fungi may be selected to decompose plant material in the digestive tract, thus providing a source of energy to the crayfish. Procambarus clarkii is also shown to be a potential vector of plant diseases as some of the 45 isolated fungal taxa are potentially phytopathogenic.

After going unreported in the northwestern Atlantic Ocean for 18 years (1988 to 2006), the Asian tiger shrimp, Penaeus monodon, has recently reappeared in the South Atlantic Bight and, for the first time ever, in the Gulf of Mexico. Potential vectors and sources of this recent invader include: 1) discharged ballast water from its native range in Asia or other areas where it has become established; 2) transport of larvae from established non-native populations in the Caribbean or South America via ocean currents; or 3) escape and subsequent migration from active aquaculture facilities in the western Atlantic. This paper documents recent collections of P. monodon from the South Atlantic Bight and the Gulf of Mexico, reporting demographic and preliminary phylogenetic information for specimens collected between North Carolina and Texas from 2006 through 2012. The increased number of reports in 2011 and 2012, ranging from 102 mm to 298 mm total length, indicates that an adult population is present in densities sufficient for breeding, which is indicative of incipient establishment. Based on these reports of P. monodon, its successful invasion elsewhere, and its life history, we believe that this species will become common in the South Atlantic Bight and Gulf of Mexico in less than 10 years. Penaeus monodon is an aggressive predator in its native range and, if established, may prey on native shrimps, crabs, and bivalves. The impacts of an established P. monodon population are potentially widespread (e.g., alterations in local commercial fisheries, direct and indirect pressures on native shrimp, crab and bivalve populations, and subsequent impacts on the populations of other predators of those organisms) and should be considered by resource managers. The impacts of P. monodon on native fauna and the source(s) or vector(s) of the invasion, however, remain unknown at this time.

Approximately ten to 15 generations after first inoculation, two invasive goby species Neogobius melanostomus and Ponticola kessleri have dispersed and established rapidly the upper Danube River. Population genomic amplified length polymorphism (AFLP) data show that the genome of the more recent newcomer, i.e. the globally invasive N. melanostomus, is significantly differentiated to a comparatively large degree (~ 5%) and exhibits pronounced small-scale population structure along a recently invaded 200 km river section. MtDNA haplotype identity over N. melanostomus samples suggests that an admixture of phylogenetically strongly differentiated source populations is unlikely. Fine-scaled local genetic population structure of N. melanostomus as deduced from Bayesian assignment tests suggest a trisection of the upper Danube instead of a clinal pattern: one downstream sample is assigned together with distant upstream samples to one population cluster. A second cluster comprises central samples, whereas two samples from the margins of this central region appear to have mixed ancestry. AFLP genome scan results indicate this population structure is strongly correlated with extrinsic (geographic) parameters, i.e. migration barriers of anthropogenic origin. However, divergence of at least one AFLP locus correlates positively with a proxy for trophic differentiation, i.e. variation of white muscle δ15N stable isotope signature. In contrast to N. melanostomus, no significant population differentiation was detectable in P. kessleri along the analyzed invasion pathway. In genome scans of P. kessleri, variation of a single locus is strongly positively correlated with an extrinsic parameter combination but not with any ecological parameter.

Invasive species have the ability to rapidly and extensively alter native ecosystems, and there is accumulating evidence to suggest that the introduction of invasive hosts can have influences on parasite transmission in native communities. In 2002, the aquatic snail Bithynia tentaculata was discovered in the Upper Mississippi River (UMR) where it now co-occurs with several native snails and their parasites. The goal of this study was to determine the competencies of a native snail (Physa gyrina) and an invasive snail (B. tentaculata) after controlled exposure to a native parasite species (Echinostoma revolutum). Results of our laboratory experiment indicated no difference in either the prevalence or intensity of infection between native and invasive snails, which was unexpected given past work on B. tentaculata. In addition, infection had no discernible influence on host life-history traits such as growth and survival. Together, these results may have a number of consequences for hosts and parasites within the UMR region. First, the presence of an additional competent host in the snail assemblage may reduce infection risk for native snail species through parasite dilution. Second, the occurrence of a competent invasive host may increase the transmission of E. revolutum to native definitive host species such as waterfowl and mammals. Ultimately, a better understanding of how native parasites cycle through the UMR snail assemblage could allow us to better predict: 1) transmission/invasion outcomes in the UMR and 2) the potential alterations that may occur in ecosystems at high risk of B. tentaculata invasion.

We present a comprehensive overview of distribution data of non-indigenous mollusc species in Lithuanian inland waters. The data are based on our own observations obtained during 2007–2013 as well as on published and unpublished records from the last 80 years. Four non-indigenous species have been reported to occur in Lithuanian freshwaters: Dreissena polymorpha, Lithoglyphus naticoides, Potamopyrgus antipodarum and Physella acuta. The last species, however, has not been found in Lithuania since the 1950s. D. polymorpha is the most widespread non-indigenous mollusc species in Lithuania. It was observed in 159 out of 226 investigated localities. The other species are less common. L. naticoides was recorded in 43 sites, whereas P. antipodarum was found in 35 localities. In addition to the possible reappearance of P. acuta, four more mollusc species which are currently absent from Lithuanian freshwaters have been reported as non-indigenous from neighbouring countries and thus might potentially invade Lithuanian inland waters in the future.

The colonial tunicate Didemnum vexillum Kott, 2002, was introduced to New England in the 1980s and by 2000 it was widespread. This highly invasive species spreads by larval release and fragmentation. We tested the ability of D. vexillum fragments to reattach to natural (eelgrass Zostera marina (Linnaeus, 1753)) and artificial (plastic container) substrates during late fall and early winter. On average, 77% of D. vexillum fragments reattached to eelgrass and plastic in water temperatures between 6 and 10°C. Eelgrass appeared to facilitate D. vexillum reattachment success in early winter but this tendency should be further investigated.

Between mid-December 2011 and mid-January 2012 an unusual mixture of ctenophores was observed and collected at Kerteminde harbor (Great Belt, Denmark). In addition to native zooplanktivorous species Pleurobrachia pileus (O.F. Müller, 1776) and Bolinopsis infundibulum (O.F. Müller, 1776), non-native zooplanktivorous Mnemiopsis leidyi A. Agissiz, 1865 and their predator Beroe cucumis Fabricius, 1780 that had earlier been recorded in the area, two more predators on zooplanktivorous ctenophores were recorded in inner Danish waters: Beroe ovata sensu Mayer and Beroe gracilis Künne, 1939. The identity of B. ovata was confirmed using nuclear marker 18S. Identification of B. gracilis was based on morphology. The presence of the observed mixture of ctenophores in Great Belt may predict future faunal changes in Danish and perhaps other temperate coastal waters.