Failure to diverge in African Great Lakes: The case of Dolicirroplectanum lacustre gen. nov. comb. nov. (Monogenea,Diplectanidae) infecting latid hosts

Speciation of fish in the African Great Lakes has been widely studied. Surprisingly, extensive speciation in parasites was only recently discovered in these biodiversity hotspots, notably in monogeneans (Platyhelminthes) from Lake Tanganyika. Diplectanum is a monogenean genus of which only a single species is known from the Great Lakes: Diplectanum lacustre (Diplectanidae) living on lates perches (Latidae) of Lake Albert. Despite their primary marine origin, latids have diversified in African freshwaters including several Great Lakes. In better-studied marine diplectanid species, incongruence between morphological and genetic differentiation was documented. As freshwater systems provide more opportunities for speciation than the marine realm, we ask whether diplectanids of Lates spp. of the Great Lakes underwent similar diversification as their hosts. Fresh and museum specimens of five African latid species (Lates angustifrons, L. mariae, L. microlepis, L. niloticus, L. stappersii) were examined for the presence of monogenean gill parasites. Monogeneans were characterised morphologically via morphometrics of sclerotised structures and genetically using nuclear and mitochondrial markers. Continuous morphological variation was documented in these parasites. In addition, the genetic distance, based on the COI region, between parasites of geographically isolated host species did not reach the level typically associated with distinct diplectanid species. Therefore, a single species of a newly described genus, Dolicirroplectanum lacustre gen. nov. comb. nov. is suggested to infect latid species in the examined basins. We discuss this parasite’s failure to diverge in the light of the congruence between the rate of molecular evolution in COI and host historical distribution.     

Quagga mussel (Dreissena rostriformis bugensis) selective feeding of phytoplankton in Saginaw Bay

Experiments from May to December measuring selective grazing and egestion of different phytoplankton taxa in natural Saginaw Bay (Lake Huron) seston by shallow-water morph quagga mussels (Dreissena bugensis rostriformis) showed that the mussels were highly selective filter feeders and that their net clearance rates on different species ranged widely, resulting in food consumption that was strongly driven by seasonal phytoplankton dynamics. Overall, net clearance rates by quagga mussels on the entire phytoplankton assemblage were similar to those observed for zebra mussels (Dreissena polymorpha) during the 1990s. Phytoplankton taxon, rather than size, was more important to food selection since quagga mussels cleared similar sized but different species of algae at very different rates. In contrast to many studies with zebra mussels, larger-sized algae such as Dinobryon divergens, Aulacoseira italica, Fragilaria crotonensis, and Anabaena were cleared at high rates and rejected at lower rates than many smaller species within the same broad taxonomic group. We suspect that these differences between dreissenid species do not stem from species differences but methodological factors and phytoplankton composition of systems studied. Small-sized diatoms, green algae with thick cell walls (Scenedesmus and Oocystis), and colonial cyanobacteria with gelatinous sheaths (Aphanocapsa, Chroococcus, and Microcystis) were cleared at low rates and rejected in high proportion in pseudofeces or feces during all seasons. We describe the likely mechanisms of pre- and post-ingestive behavior that explain these differences, which relate to phytoplankton size, morphology, cell wall characteristics, and chemical composition. Changes in the Great Lakes phytoplankton communities are consistent with mussel grazing preferences.     

Diatoms from the Great Lakes. I. Rare or Poorly known Species of the Genera Diploneis,Oestrupia and Stauroneis

Eleven taxa of diatoms occurring in the Great Lakes which have not been adequately treated in the North American literature are briefly described and figured. Taxa treated include 4 species of Diploneis, 1 species and one variety of Oestrupia, and 1 species and 4 infraspecific taxa of Stauroneis. The presently known distribution of these entities in the Great Lakes and their ecological and distributional affinities are discussed.     

The lobed-lipped species of Haplochromis (Teleostei,Cichlidae) from Lake Edward,two instead of one

Thickened lips have evolved several times within the cichlid flocks of the East African Great Lakes. This distinct and easily recognisable phenotype is a model trait to study convergent evolution. Lake Edward (Eastern Africa) contains a unique cichlid assemblage, which has remained largely understudied. Hitherto, only one cichlid species with lobed lips, Haplochromis labiatus, was known from this lake. This species has a blunt snout and rounded and mostly retrognathous jaws. However, we found specimens with lobed lips, but with acute snouts and slender and mostly prognathous jaws. These belong to a species, hitherto unknown to science: H. lobatus sp. nov. Both species occur sympatrically. We evaluated the morphological diversity within these species by investigating a total of 112 specimens using traditional and geometric morphometric approaches. Both species are formally (re)described and show a relatively large variation in their trophic morphologies, which complicates identification. Both have a small gape, stout outer teeth that strongly decrease in size laterad, and a lower jaw set anteriorly with procumbently-implanted outer teeth. Haplochromis labiatus differs from H. lobatus sp. nov. by a straight to convex vs. straight to concave head, a slightly shorter and broader lower jaw (27.7–34.3 vs. 31.2–40.7% HL; 71.4–92.4 vs. 48.5–70.5% LJL), and lobed lips that are thickened uniformly over their whole lengths vs. medially enlarged. Gut content observations revealed that both species have an insectivorous diet. While both exploit similar food sources, their morphological differences presumably prevent them from entering into direct ecological competition.     

Diatoms from the Great Lakes. II. Some Rare or Poorly Known Species of the Genus Navicula

Twenty-one taxa of the diatom genus Navicula which are known to occur in the Great Lakes but have not been adequately treated in the North American literature are described and figured. The observed Great Lakes distribution and ecological affinities of these entities are discussed.     

Diatom responses to 20th century shoreline development and climate warming in three embayments of Georgian Bay,Lake Huron

We used high-resolution diatom-based paleolimnological techniques to assess the effects of shoreline development and recent climate warming on three large embayments of Georgian Bay, Lake Huron (two impacted and one minimally impacted by shoreline development). The sedimentary diatom assemblages recorded subtle shifts at the impacted sites (North and South Bays) as a result of the establishment of permanent settlements and recreational resorts around the turn of the 20th century. No turn-of-the-century changes were observed at the reference site (Tadenac Bay). The abrupt increase in epiphytic Cocconeis placentula and benthic fragilarioid taxa during the ~1950s at the shallower impact site (South Bay) was likely due to increased habitat provided by macrophytes. The increase in relative abundances of pennate (Asterionella formosa and Fragilaria crotonensis) and/or small centric (Cyclotella ocellata, C. comensis, and C. gordonensis) planktonic diatoms across the three sites after the 1970s suggests that recent warming-mediated changes to thermal properties (and related effects) are driving biological changes in these embayments. These recent diatom compositional changes are consistent with similar trends reported across Ontario and the Laurentian Great Lakes, where warming and its effects on aquatic ecosystem processes often favor small-celled centric diatoms. Differences in the timing and nature of diatom responses to similar environmental stressors across the three embayments highlight the importance of understanding site-specific characteristics when interpreting changes in diatom assemblages in paleolimnological records from the Laurentian Great Lakes.     

Using Microfossil Remains in Lake Sediments to Examine the Invasion of Eubosmina coregoni (Cladocera,Bosminidae) in Lake of the Woods,Ontario, Canada

Many nonindigenous species (NIS) present in the Laurentian Great Lakes are expanding their ranges to inland lakes and streams. This study used cladoceran microfossils to examine the invasion history of Eubosmina coregoni, the first known nonindigenous zooplankter to invade Lake of the Woods (LOW), Ontario, Canada. Sediment cores from 16 sites in LOW were used to analyze broad-scale presence/absence of E. coregoni prior to human development (bottom sediment samples) in comparison with present-day distribution (top sediment samples). E. coregoni had the highest relative abundance in the northern and eastern regions of LOW and the abundance of all cladoceran remains was low in the southern region of the lake. A long core (time core) from Clearwater Bay provided a more detailed historical account of E. coregoni's abundance in the northern region of LOW, indicating that E. coregoni was first detected in the lake in the early 1990s, approximately 25 years after it was discovered in the Laurentian Great Lakes. Results obtained in this study have illuminated temporal and spatial patterns of colonization of this inland water body. Study of the early invasion dynamics of NIS in these inland lakes may aid in the prevention of future invasions of taxa that have already altered the food web dynamics in the Laurentian Great Lakes.     

Exotic and Invasive Aquatic Plants in Great Lakes Coastal Wetlands: Distribution and Relation to Watershed Land Use and Plant Richness and Cover

We use data from inundated-area surveys of 58 coastal wetlands spanning a gradient of anthropogenic impacts across all five Laurentian Great Lakes to describe the distribution of nine exotic and invasive taxa of aquatic plants. We found plants that were exotic or have invasive strains to be substantially more prevalent in wetlands in Lakes Erie and Ontario than in Lakes Superior and Huron, with Lake Michigan wetlands intermediate. Najas minor (slender naiad), Butomus umbellatus (flowering rush), and Hydrocharis morsus-ranae (European frogbit) were restricted to the lower lakes and rarely dominant. Myriophyllum spicatum (Eurasian milfoil), Potamogeton crispus (curly pondweed), Lythrum salicaria (purple loosestrife), Phalaris arundinacea (reed canary grass), Phragmites australis (common reed), and Typha sp. (cattail) were more widespread and except for P. crispus, often among the dominant taxa. None of the submerged or floating-leaf exotic taxa were associated with altered total plant cover or richness, although M. spicatum, P. crispus, and native Stuckenia pectinatus (sago pondweed) were positively associated with agricultural intensity in the watershed (a surrogate for nutrient loading). Emergent P. australis, L. salicaria, and Typha were more likely to be present and dominant as agricultural intensity increased, and were associated with elevated emergent cover and decreased emergent genera richness. Effects of dominant taxa on plant cover and richness were readily detected using ordinal data from 100 m inundated segments but were harder to discern with data aggregated to the wetland scale. The sum of shoreline-wide abundance scores for four easily identified taxa (S. pectinata, P. australis, Typha, and L. salicaria) is proposed as a rapidly-measured indicator of anthropogenic disturbance across the Great Lakes.     

What's in a name? Taxonomy and nomenclature of invasive gobies in the Great Lakes and beyond

The species identities, scientific names, and relationships of Eurasian gobies that invaded the Laurentian Great Lakes – and other species that are predicted to invade in the future – are evaluated here using recently resolved DNA characters. The Round Goby and the Freshwater Tubenose Goby entered the Great Lakes ca. 1990 via ballast water originating from Black Sea ports. The Round Goby spread extensively throughout the Great Lakes and adjacent rivers, whereas the Freshwater Tubenose Goby recently began to expand its range. Both species also are widely invasive in Eurasia, dispersing via canals and shipping. Several of their relatives – the Monkey, Racer, and Bighead gobies – also are invasive in Eurasia, and are predicted to invade the Great Lakes. We discuss results from phylogenetic analyses of DNA sequences from 4 mitochondrial and nuclear gene regions, and provide a revision of their scientific nomenclature. The Freshwater Tubenose Goby was redefined as Proterorhinus semilunaris, which is markedly different and distinctive from the Marine Tubenose Goby Proterorhinus marmoratus. The genus Neogobius, as formerly defined, contained multiple evolutionary lineages and incorrect scientific names. We thus restricted Neogobius to just 4 species—including the Round Goby Neogobius melanostomus and the Black Sea Monkey Goby Neogobius fluviatilis. Several previously recognized subgenera, which were incorrectly grouped in Neogobius, were elevated to the level of genera. Notably, the Racer Goby became Babka gymnocephalus and the Bighead Goby now is Ponticola kessleri. These changes made the names consistent with their true relationships and species characters, which are essential for identifying and characterizing these gobies in invasive and native habitats.     

European frogbit (Hydrocharis morsus-ranae) invasion facilitated by non-native cattails (Typha) in the Laurentian Great Lakes

Plant-to-plant facilitation is important in structuring communities, particularly in ecosystems with high levels of natural disturbance, where a species may ameliorate an environmental stressor, allowing colonization by another species. Increasingly, facilitation is recognized as an important factor in invasion biology. In coastal wetlands, non-native emergent macrophytes reduce wind and wave action, potentially facilitating invasion by floating plants. We tested this hypothesis with the aquatic invasive species European frogbit (Hydrocharis morsus-ranae; EFB), a small floating plant, and invasive cattail (Typha spp.), a dominant emergent, by comparing logistic models of Great Lakes-wide plant community data to determine which plant and environmental variables exerted the greatest influence on EFB distribution at multiple scales. Second, we conducted a large-scale field experiment to evaluate the effects of invasive Typha removal treatments on an extant EFB population. Invasive Typha was a significant predictor variable in all AIC-selected models, with wetland zone as the other most common predictive factor of EFB occurrence. In the field experiment, we found a significant reduction of EFB in plots where invasive Typha was removed. Our results support the hypothesis that invasive Typha facilitates EFB persistence in Great Lakes coastal wetlands, likely by ameliorating wave action and wind energy. The potential future distribution of EFB in North America is vast due in part to the widespread and expanding distribution of invasive Typha and other invading macrophytes, and their capacity to facilitate EFB's expansion, posing significant risk to native species diversity in Great Lakes coastal wetlands.     

Status of the major aquaculture carps of China in the Laurentian Great Lakes Basin

There is concern of economic and environmental damage occuring if any of the four major aquacultured carp species of China, black carp Mylopharyngodon piceus, bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, or grass carp Ctenopharyngodon idella, were to establish in the Laurentian Great Lakes. All four are reproducing in the Mississippi River Basin. We review the status of these fishes in relation to the Great Lakes and their proximity to pathways into the Great Lakes, based on captures and collections of eggs and larvae. No black carp have been captured in the Great Lakes Basin. One silver carp and one bighead carp were captured within the Chicago Area Waterway System, on the Great Lakes side of electric barriers designed to keep carp from entering the Great Lakes from the greater Mississippi River Basin. Three bighead carp were captured in Lake Erie, none later than the year 2000. By December 2019, at least 650 grass carps had been captured in the Great Lakes Basin, most in western Lake Erie, but none in Lake Superior. Grass carp reproduction has been documented in the Sandusky and Maumee rivers in Ohio, tributaries of Lake Erie. We also discuss environmental DNA (eDNA) results as an early detection and monitoring tool for bighead and silver carps. Detection of eDNA does not necessarily indicate presence of live fish, but bigheaded carp eDNA has been detected on the Great Lakes side of the barriers and in a small proportion of samples from the western basin of Lake Erie.     

Distribution,seasonality and putative origin of the non-native red alga Bangia atropurpurea (Bangiales,Rhodophyta) in the Laurentian Great Lakes

Bangia atropurpurea was first observed in Lake Erie in 1964 and subsequently spread to the lower Laurentian Great Lakes by the mid to late 1970s. The present study was initiated to examine the recent distribution of B. atropurpurea in the Great Lakes, the seasonal variation of the alga and the putative origin of this species based on DNA sequence analysis. From surveys in 1995 and 2002, this species has clearly spread, with newly identified populations observed in Lakes Huron, Michigan, Georgian Bay and the St. Lawrence River. Morphological analyses showed that Great Lakes populations from individual lakes or neighboring populations did not group together in cluster analyses. Correlation analysis, however, revealed significant relationships between the presence or absence of Bangia among the studied sites with pH and specific conductance as those locations that had stable populations had a mean pH and conductance of 8.2 and 353 μS·cm^− 1 respectively. Seasonal variation in morphology of a population from Burlington, Ontario (Lake Ontario, Canada) was examined monthly for one year. Maximum filament length occurred in April, with the greatest diameter and archaeospore production observed in May. Significant correlations were also noted for many morphological characteristics with water temperature, population height on the shoreline relative to the waterline and total phosphorus. Collections of B. atropurpurea analyzed from the Great Lakes were observed to be identical in sequence to collections of European freshwater Bangia in the cox2–3 gene spacer, the nuclear internal transcribed spacers (ITS 1 and 2) and the 5.8S rRNA gene (between the small and large subunits of the rRNA gene). These results suggest a recent European origin; however, further global collections of B. atropurpurea and microsatellite analyses are necessary to confirm this hypothesis.     

Nearshore benthic blooms of filamentous green algae in Lake Baikal

For the first time, species of the genus Spirogyra, non-typical of the open nearshore waters of Lake Baikal, formed algal mats with Ulothrix zonata, Ulothrix tenerrima, and Ulothrix tenuissima near the village of Listvyanka, Russia. Normally widely distributed in the 0- to 1.5-m depth range, the growth of U. zonata was now evident and dominant (63% of the biomass) in the 2- to 5-m depth range. The overgrowth of the lake bottom by filamentous green algae, changes in distributional boundaries, the emergence and mass development of species of the genus Spirogyra, the presence of the eutrophic diatom indicator Fragilaria capucina var. vaucheriae, elevated abundances of coliform bacteria, and elevated levels of nutrients suggest an early stage of cultural eutrophication in the nearshore of Lake Baikal near Listvyanka, a popular tourist destination. The unusual abundance of Fragilaria associated with the filamentous green algae consisted of long-ribbon colonies of F. capucina var. vaucheriae, a eutrophic species, wound around the filamentous green algae, enhancing the dense algae mats. Historically dominant species, such as Didymosphenia geminata, Tetraspora cylindrica var. bullosa, and Draparnaldioides baicalensis typically observed at deeper depths of Lake Baikal, are now subdominants or minor species in the nearshore along the shoreline near Listvyanka.     

DNA barcoding vs. morphological identification of larval fish and embryos in Lake Huron: Advantages to a molecular approach

The Great Lakes provide habitat to over 160 species of freshwater fish, many of which are ecologically and economically important. Concern for management and conservation of declining fish populations makes it important that accurate identification techniques are used for environmental monitoring programs. DNA barcoding may be an effective alternative to morphological identification for industrial monitoring programs of larval and embryonic fish, but comparisons of the two approaches with species from the Great Lakes are limited. It may be particularly important to examine this issue in the Great Lakes because a relatively young group of post-glacial fish species are present which may be difficult to resolve using morphology or genetics. Six hundred and fifty seven larval fish were identified from Lake Huron (Ontario, Canada), using morphology and DNA barcoding. DNA barcoding was used to identify 103 embryos that morphology could not identify. Morphological identification and DNA barcoding had a percent similarity of 76.9%, 96.6% and 96.6% at the species, genus, and family levels, respectively. Thirty-seven specimens were damaged and unidentifiable using morphology; 35 of these were successfully identified using DNA barcoding. However, 23 other specimens produced no PCR product for barcoding using 2 different primer sets. Discrepancies between morphology and DNA barcoding were driven by two major factors: inability of cytochrome oxidase I to resolve members of the genus Coregonus and limited resolution of morphological features for Catostomus. Both methods have pros and cons; however, DNA barcoding is more cost-effective and efficient for industrial monitoring programs.     

Brachionus leydigii (Monogononta: Ploima) reported from the western basin of Lake Erie

Several species of non-indigenous planktonic invertebrates have historically been introduced to the Laurentian Great Lakes. Previous introductions of non-indigenous planktonic invertebrates to the Great Lakes have been crustacean zooplankton, specifically Cladocera and Copepoda. This report documents the first known occurrence of Brachionus leydigii var. tridentatus (Zernov, 1901) in Lake Erie and possibly the first detection of a non-indigenous rotifer species in the Laurentian Great Lakes. The specimen was collected from a U.S. EPA monitoring station in the western basin of Lake Erie on April 4, 2016.     

An alternative hypothesis to invasional meltdown in the Laurentian Great Lakes region: General facilitation by Dreissena

Invasional meltdown, where established non-indigenous species facilitate the establishment and spread of newly arriving non-indigenous species, may contribute to the increasing rate of biological invasions. The Laurentian Great Lakes have been used as an example of invasional meltdown, but our results suggest that this may not be the case. We propose that the increased numbers of facilitative interactions are not due to an invasion meltdown, but rather a strongly interacting species, such as Dreissena, promoting population level changes in both native and non-indigenous species. Dreissena are the facilitator in the majority of reported facilitations of non-indigenous species, and those non-indigenous species have not yet led to more invasions. Further, our results show that Dreissena facilitate non-indigenous and native species similarly. Literature reviews showed little evidence that Dreissena facilitate fish or are facilitated by phytoplankton. Consequently, the observed pattern of species interactions in the Great Lakes does not conform to the definition of invasional meltdown. We suggest that Dreissena cause strong interactions and change the benthos in a way that facilitates many organisms (native and non-indigenous), but that system-wide invasional meltdown is not occurring in the Great Lakes.     

The discovery of the nonindigenous,mottled fingernail clam, Eupera cubensis (Prime, 1865) (Bivalvia: Sphaeriidae) in the Chicago Sanitary and Ship Canal (Illinois River Drainage), Cook County,Illinois

The nonindigenous mottled fingernail clam, Eupera cubensis is reported from the Upper Mississippi River Basin for the first time. This record represents a significant northern range expansion for the species in the United States. It appears to be presently confined to a 35-km stretch of the Chicago Sanitary and Ship Canal (CSSC), an artificial waterway that connects the Mississippi River drainage to the Great Lakes. Although the introduction of this species to the Great Lakes basin poses uncertain risks to the general aquatic community, the immediate effects of Eupera cubensis on the fauna of the CSSC are expected to be minimal.     

Metazoan Parasites of Introduced Round and Tubenose Gobies in the Great Lakes: Support for the “Enemy Release Hypothesis”

Recent invasion theory has hypothesized that newly established exotic species may initially be free of their native parasites, augmenting their population success. Others have hypothesized that invaders may introduce exotic parasites to native species and/or may become hosts to native parasites in their new habitats. Our study analyzed the parasites of two exotic Eurasian gobies that were detected in the Great Lakes in 1990: the round goby Apollonia melanostoma and the tubenose goby Proterorhinus semilunaris. We compared our results from the central region of their introduced ranges in Lakes Huron, St. Clair, and Erie with other studies in the Great Lakes over the past decade, as well as Eurasian native and nonindigenous habitats. Results showed that goby-specific metazoan parasites were absent in the Great Lakes, and all but one species were represented only as larvae, suggesting that adult parasites presently are poorly-adapted to the new gobies as hosts. Seven parasitic species are known to infest the tubenose goby in the Great Lakes, including our new finding of the acanthocephalan Southwellina hispida, and all are rare. We provide the first findings of four parasite species in the round goby and clarified two others, totaling 22 in the Great Lakes—with most being rare. In contrast, 72 round goby parasites occur in the Black Sea region. Trematodes are the most common parasitic group of the round goby in the Great Lakes, as in their native Black Sea range and Baltic Sea introduction. Holarctic trematode Diplostomum spathaceum larvae, which are one of two widely distributed species shared with Eurasia, were found in round goby eyes from all Great Lakes localities except Lake Huron proper. Our study and others reveal no overall increases in parasitism of the invasive gobies over the past decade after their establishment in the Great Lakes. In conclusion, the parasite “load” on the invasive gobies appears relatively low in comparison with their native habitats, lending support to the “enemy release hypothesis.”     

Genetic Analysis of the Chinese Mitten Crab (Eriocheir sinensis) Introduced to the North American Great Lakes and St. Lawrence Seaway

The Chinese mitten crab (Eriocheir sinensis) is an invasive organism of concern, with established non-native populations in Europe and California, USA. The species is thought to pose a risk to other North American waterways, including the Great Lakes and St. Lawrence Seaway. Since 1965, there have been sixteen confirmed adult E. sinensis caught in the North American Great Lakes or adjoining waterways. Analysis of their mitochondrial DNA sequence variation for part of the cytochrome c oxidase subunit I gene discerned three haplotypes among seven individuals (caught between 1973 and 2005), identical to common haplotypes in Europe. Analysis of mitochondrial haplotype frequencies and shipping patterns suggests that E. sinensis has been introduced to the Great Lakes from Europe, although we are unable to preclude native Asian populations as putative sources. The species is catadromous, migrating between salt and fresh water to complete its life cycle. This trait makes it unlikely that E. sinensis will establish a breeding population in the Great Lakes proper, which are separated from saltwater by a considerable distance and significant instream barriers such as waterfalls and navigation locks. However, the recent discovery of two confirmed mitten crabs in the St. Lawrence River, which could be more readily colonized, underscores the risk posed by the repeated introduction of this species into the Great Lakes and St. Lawrence Seaway.     

European Valve Snail Valvata piscinalis (Müller) in the Laurentian Great Lakes Basin

Previously reported from the lower Great Lakes basin and St. Lawrence and Hudson rivers, the nonindigenous gastropod Valvata piscinalis was found for the first time in Superior Bay (Minnesota) of Lake Superior, Lake Michigan (Wisconsin), and Oneida Lake (New York) of the Lake Ontario basin. This snail was not abundant in Lakes Superior and Michigan, whereas in eutrophic Oneida Lake it reached a maximum density of 1,690 individuals/m² (mean density = 216 individuals/m²). Human-mediated disturbances could facilitate the range extension of this snail by providing dispersal opportunities (e.g., canals, shipping traffic) or increasing nutrients (e.g., eutrophication). A native of the Palaearctic region, V. piscinalis has colonized sites across the Great Lakes basin, suggesting that it will likely become common in disturbed Great Lakes areas.