Invasive and non-invasive lineages in Xenostrobus (Bivalvia: Mytilidae)

The mussel genus Xenostrobus comprises eight named extant species from the Indo-West Pacific, including Xenostrobus inconstans, Xenostrobus pulex and Xenostrobus securis from Australia, the latter two also occurring in New Zealand. Xenostrobus species are predominantly restricted to estuaries or sheltered marine habitats although X. pulex inhabits the rocky intertidal on open coasts. Xenostrobus has recently been suggested to be congeneric with the freshwater invasive species Limnoperna fortunei. Xenostrobus securis is itself invasive in the Far East and Europe. This study employed DNA sequences from cytochrome c oxidase (COI), the D1 expansion region of 28S rRNA and the internal transcribed spacers of the ribosomal cistrons to investigate species relationships and habitat transitions in Australasian Xenostrobus. It is unlikely that Xenostrobus and Limnoperna are congeneric as their COI sequences are very different. There was unexpected complexity in defining Xenostrobus species. Xenostrobus pulex from New Zealand is probably a distinct species to the Australian taxon of that name with the name X. neozelanicus available for that taxon. Xenostrobus inconstans and Australian X. pulex were not reciprocally monophyletic in COI analyses. The phylogeography of the COI haplotypes of X. securis suggests that it may be a cryptic species complex, although this possibility could not be confirmed by sequences of the other genes.     

Fine-scale spatial partitioning of genetic variation and evolutionary contestability in the invasive estuarine mussel Xenostrobus securis

Initial studies of Australian populations of the widely invasive mussel Xenostrobus securis raised the possibility of non-random spatial partitioning within estuaries of mitochondrial DNA (mtDNA) clades that have dispersed intercontinentally and those that have not. A fine-scale phylogeographic investigation was made to examine this possibility using cytochrome c oxidase DNA sequences and data from five microsatellite loci developed here. X. securis in the study region was found to comprise multiple robustly supported mtDNA clades, many of which were genetically very distinct. Frequently, the clades comprised numerous haplotypes that have narrow ranges and may have evolved in situ within drainages or nearby. Microsatellite data reveal significant intra- and inter-drainage differentiation but at lower levels than mtDNA. Variation in mtDNA appears to reflect not only recolonization after infrequent local extinction within drainages but also the low probability of migratory haplotypes successfully establishing during evolutionary contests, with resident haplotypes having selective or demographic advantages derived from local occupation. The patterns of mtDNA haplotype distribution suggest that central New South Wales is the source of the internationally invasive lineages of X. securis.     

The mussel <Emphasis Type="Italic">Xenostrobus securis</Emphasis>: a well-established alien invader in the Ria de Vigo (Spain,NE Atlantic)

Biological and habitat characterization of the non-indigenous invasive species Xenostrobus securis was undertaken in the Ria de Vigo. This study included genetic identification of mussel samples collected from introduced and endemic areas, and the assessment of mussel size, population abundance, geographic distribution, pathological condition, and sediment composition of substrata type. The mussel had a marked patchy distribution, being more abundant in brackish sites with fine sediments and high organic matter content. Pathological analysis revealed that X. securis does not play any role as vector for introducing allochthonous pathogens in the Ria de Vigo. Nevertheless, depending on its invasiveness potential, the mussel could be a key host favouring spreading and epizootic outbreaks of marteliosis which is known to be harmful for local bivalve populations. Phylogenetic analyses of the COI gene placed all the resulting sequences in a clade within the genus Xenostrobus and its phylogeny congruent with an Australian/Pacific origin. The COI tree suggests two historical introductions in European waters. One of these invasions seems to have started in Galicia, moving from there towards Italy and France, while the geographical spread of the second invasion cannot be deciphered, although the Australian/Pacific origin of this invasion seems very possible. The 18S network is congruent with one invasion starting in Galicia or in Italy, as the Australian haplotype is closely related to the haplotype found in these areas. Several hypotheses accounting for the colonization history of this species in Galician waters are discussed.     

Molecular Detection of <Emphasis Type="Italic">Xenostrobus securis</Emphasis> and <Emphasis Type="Italic">Mytillus Galloprovincialis</Emphasis> Larvae in Galician Coast (Spain)

The mussel species Xenostrobus securis from New Zealand was detected in the Spanish coast recently, in the mouth of the Verdugo River into the Vigo Ria. In view of the great importance of the farm mussel sector in this region, the presence of this alien species greatly concerned producers and administration authorities, because of its potential medium- or long-term effects on the autochthonous species, Mytilus galloprovincialis, an important marine resource widely exploited in this location. The goal of this study was to develop a DNA-based technique to identify X. securis and M. galloprovincialis larvae in plankton samples, which would allow monitoring for the presence of X. securis in different points of the Vigo Ria. The techniques used were simplex and multiplex polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), and fragment analysis. The application of this system to planktonic samples could be an effective means to assess the presence of the alien species, allowing monitoring if its dispersion is increasing, or on the contrary, if its distribution is restricted to the mouth of the Verdugo River, where X. securis was first detected. In addition, the application of this system at different times could be useful to assess the presence of larvae of these two species in the plankton.     

Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control?

Introduced species are often considered to be a threat to residents, but not all reciprocal trends may reflect species interaction. In the northern German Wadden Sea, native mussel Mytilus edulis beds are declining and overgrown by introduced Pacific oysters Crassostrea gigas and slipper limpets Crepidula fornicata. We review the population development of the three species and analyse whether the invading species may be responsible for the decline of native mussels. The Pacific oyster predominately settles on mussel beds in the intertidal and the slipper limpet dominates around low water line. We compare the development of mussels and invaders in two subregions: mussel beds near the islands of Sylt and Amrum decreased both in the presence (Sylt) and absence (Amrum) of the two invading species and more detailed investigations could not confirm a causal relationship between the increasing invaders and decreasing mussel beds. There is evidence that the decline of mussel beds is mainly caused by failing spatfall possibly due to mild winters, whereas the increase in slipper limpets and oysters is facilitated by mild winters and warm summers, respectively. We conclude that changing species composition is a result of the climatic conditions in the last decade and that there is no evidence yet that the exotic species caused the decline of the natives. It remains an open question whether the species shift will continue and what the consequences for the native ecosystem will be.     

Community dynamics of intertidal soft-bottom mussel beds over two decades

Macrozoobenthos communities in the North Sea showed pronounced changes over the past decade in relation to an increasing number of invasive species and climate change. We analysed data sets spanning 22 years on abundance, biomass and species composition of intertidal soft bottom mussel beds near the island of Sylt (German Bight) in the Northern Wadden Sea, based on surveys from 1983/1984, 1990, 1993 and from 1999 to 2005. Mussel bed area and blue mussel biomass decreased, and a change in the dominance structure in the associated community comparing 1984 to mid-1990s with the period from 1999 to 2005 was observed. Coverage of the mussel beds with the algae Fucus vesiculosus decreased since the end of the 1990s. Within the study period biomass and densities of the associated community increased significantly. Dominance structure changed mainly because of increasing abundances of associated epibenthic taxa. Apart from the Pacific oyster Crassostrea gigas all other alien species were already present in the area during the study period. Community changes already started before Pacific oysters became abundant. An attempt is made to evaluate effects on the observed changes of decreasing mussel biomass, ageing of mussel beds, decreasing fucoid coverage and increasing abundances of invader. All four factors are assumed to contribute to changing community structure of intertidal mussel beds.     

Introduced Pacific oysters (Crassostrea gigas) in the northern Wadden Sea: invasion accelerated by warm summers?

Among the increasing number of species introduced to coastal regions by man, only a few are able to establish themselves and spread in their new environments. We will show that the Pacific oyster (Crassostrea gigas) took 17 years before a large population of several million oysters became established on natural mussel beds in the vicinity of an oyster farm near the island of Sylt (northern Wadden Sea, eastern North Sea). The first oyster, which had dispersed as a larva and settled on a mussel bed, was discovered 5 years after oyster farming had commenced. Data on abundance and size-frequency distribution of oysters on intertidal mussel beds around the island indicate that recruitment was patchy and occurred only in 6 out of 18 years. Significant proportions of these cohorts survived for at least 5 years. The population slowly expanded its range from intertidal to subtidal locations as well as from Sylt north- and southwards along the coastline. Abundances of more than 300 oysters m^–2 on mussel beds were observed in 2003, only after two consecutive spatfalls in 2001 and 2002. Analyses of mean monthly water temperatures indicate that recruitment coincided with above-average temperatures in July and August when spawning and planktonic dispersal occurs. We conclude that the further invasion of C. gigas in the northern Wadden Sea will depend on high late-summer water temperatures.Communicated by H.D. Franke     

Byssus attachment strength of two mytilids in mono-specific and mixed-species mussel beds

The mussel Xenostrobus securis is endemic to the brackish waters of New Zealand and Australia, but has successfully invaded the inner Galician Rías of NW Spain, where it coexists with the indigenous mussel Mytilus galloprovincialis. In this laboratory study, the plasticity of the byssus attachment strength of two mytilids was compared by manipulating substratum, salinity, and bed assembly. M. galloprovincialis showed stronger byssus detachment strength than X. securis, despite lower byssus coverage. Both species responded similarly to the substratum, with substantially lower byssus strength on methacrylate, which offered the lowest surface free energy. Byssus detachment values for M. galloprovincialis were lower at lower salinity. In mixed beds, a number of mussels moved upwards, eventually colonising the upper layers of the assemblage. This behaviour increased byssus strength but only for X. securis. X. securis is adapted to a wide spectrum of abiotic conditions, a trait that may promote its dissemination within estuarine environments.     

Impact of the invasive parasitic copepod Mytilicola orientalis on native blue mussels Mytilus edulis in the western European Wadden Sea

Invasive species can indirectly affect native species by modifying parasite–host dynamics and disease occurrence. This scenario applies to European coastal waters where the invasive Pacific oyster (Magallana gigas) co-introduced the parasitic copepod Mytilicola orientalis that spills over to native blue mussels (Mytilus edulis) and other native bivalves. In this study, we investigated the impact of M. orientalis infections on blue mussels by conducting laboratory experiments using controlled infections with larval stages of the parasitic copepod. As the impact of infections is likely to depend on the mussels’ food availability, we also tested whether potential adverse effects of infection on mussels intensify under low food conditions. Blue mussels that were experimentally infected with juvenile M. orientalis had a significantly lower body condition (11–13%) compared with uninfected mussels after nine weeks of infection. However, naturally infected mussels from a mixed mussel and oyster bed did not significantly differ in body condition compared with uninfected mussels. Contrary to effects on mussel condition, we did not find an effect of experimental infections on clearance rates, shell growth or survival of blue mussels and no clear sign of exacerbating effects of food limitation. Our study illustrates that invasive species can indirectly affect native species via parasite co-introductions and parasite spillover. The results of this study call for the integration of such parasite-mediated indirect effects of invasions in impact assessments of invasive species.     

Predator‐induced morphological defences in two invasive dreissenid mussels: implications for species replacement

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The American slipper limpet <Emphasis Type="Italic">Crepidula fornicata </Emphasis>(L.) in the northern Wadden Sea 70 years after its introduction

In 1934 the American slipper limpet Crepidula fornicata (L.) was first recorded in the northern Wadden Sea in the Sylt-R?m? basin, presumably imported with Dutch oysters in the preceding years. The present account is the first investigation of the Crepidula population since its early spread on the former oyster beds was studied in 1948. A field survey in 2000 revealed the greatest abundance of Crepidula in the intertidal/subtidal transition zone on mussel (Mytilus edulis) beds. Here, average abundance and biomass was 141 m^–2 and 30 g organic dry weight per square metre, respectively. On tidal flats with regular and extended periods of emersion as well as in the subtidal with swift currents in the gullies, Crepidula abundance was low. The main substrate of attachment was live mussels. Compared with the years following their initial introduction, Crepidula is more abundant today and has shifted from the now extinct oyster beds to the epifaunal community of the mussel beds. Their present abundance is considerably lower than at more southern European coasts where the species may dominate the epifauna. Low winter temperatures are suggested to have limited the population expansion in the northern Wadden Sea until now. Electronic Publication     

Observation of a Bonamia sp. infecting the oyster Ostrea stentina in Tunisia, and a consideration of its phylogenetic affinities

The small non-commercial oyster Ostrea stentina co-occurs with commercially important Ostrea edulis in the Mediterranean Sea, yet its disposition with respect to the destructive pathogens Bonamia ostreae and Marteilia refringens is unknown. We began an evaluation of the Bonamia spp. infection status of O. stentina from Hammamet, Tunisia, in June 2007 using polymerase chain reaction diagnostics followed by histology and in situ hybridization. Of 85 O. stentina sampled, nine were PCR-positive for a Bonamia sp. using a Bonamia genus-specific assay; of these nine, one displayed the uninucleate microcells associated with oyster hemocytes characteristic of Bonamia spp. There was no associated pathology. DNA sequencing of the parasite from this one infected individual revealed it to be of a member of the Bonamia exitiosa/Bonamia roughleyi clade, an identification supported by positive in situ hybridization results with probes specific for members of this clade, and by the morphology of the parasite cells: nuclei were central, as in B. exitiosa, not eccentric, as in B. ostreae. There is no basis for identifying the Tunisian parasite as either B. exitiosa or B. roughleyi, however, as these species are genetically indistinguishable. Likewise, there is no basis for identifying any of the other Bonamia spp. with affinities to the B. exitiosa/B. roughleyi clade, from Argentina, Australia, Spain, and the eastern USA, as one or the other of these named species. Though they are clearly distinct from Bonamia perspora and B. ostreae, justification for drawing species boundaries among the primarily austral microcells with affinities to B. exitiosa and B. roughleyi remains elusive.     

Asexual propagations of introduced exotic macrophytes <Emphasis Type="Italic">Elodea nuttallii</Emphasis>, <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis>, and <Emphasis Type="Italic">M. propinquum</Emphasis> are improved by nutrient-rich sediments in China

An increasing number of recent studies indicate that multiple interacting factors can affect the invasion of plants. However, few studies have focused on asexual propagation and the interaction of propagation with environmental factors that regulate the invasive potential of introduced exotic species in aquatic habitats. This study was designed to investigate the differences in asexual propagation between introduced exotic and non-invasive native aquatic macrophytes in nutrient-poor and nutrient-rich sediments and to test the hypothesis that differences in asexual propagation (stem fragment production) and propagule establishment between introduced exotic and non-invasive native macrophytes are driven by sediment nutrient levels. Three exotic aquatic macrophytes (Elodea nuttallii, Myriophyllum aquaticum, and M. propinquum) recently introduced to China and their non-invasive native counterparts (Hydrilla verticillata, M. oguraense, and M. ussuriense) were used for comparison in nutrient-poor (TN 0.59 and TP 0.03 mg g⁻¹) and nutrient-rich (TN 2.35 and TP 0.10 mg g⁻¹) sediments. After 8 weeks of growth, the exotic species tended to produce more total biomass, branch biomass and apical shoots and have higher relative growth rate (RGR) than their native counterparts in nutrient-rich sediment. Rooting efficiency and root growth of exotic fragments were higher than that of native counterparts in nutrient-rich sediment, although the survival rates of fragments did not differ between native and exotic species. In addition, superior traits (rooting efficiency and root growth) of exotic species were also observed in nutrient-poor sediment, but to a lesser degree than in nutrient-rich sediment. These results suggest that asexual propagation of these three introduced exotic macrophytes is more effective in nutrient-rich sediment than in nutrient-poor sediment in China.     

Use of Geographic Information Systems to monitor and predict non-native aquatic plant dispersal through north-eastern North America

North America has a growing problem with invasive aquatic plants. At every level of the aquatic food web, long-standing checks and balances have become dramatically eroded by the introduction of non-native species. The northeastern United States contains thousands of diverse freshwater habitats, highly heterogeneous in geology and locale, where nuisance aquatic plant growth results in decreased lake water quality, interference with recreational access, degraded flood control structures, and impacts to their aesthetic quality. Early infestation and spread of exotic species is often poorly documented at local and state levels. Consequently, successful management of these species depends on continuous monitoring and definitive identification by both public officials and waterside homeowners. With new mapping capabilities employing software such as Geographic Information Systems (GIS) coupled with the growing computerization of taxonomic records and online availability of regional herbarium records, we have been able to illustrate the␣temporal and geographic spread of these species, thus enabling aquatic ecologists and managers to make predictions of future infestations. In this paper we evaluate these techniques focusing on three of the most pervasive of exotic aquatic plant species in New York State: Myriophyllum spicatum, Trapa natans and Potamogeton crispus.     

Alien fish species in Indian inland wetlands: current status and future challenges

Although wetlands are well-recognized for their biological, ecological, cultural, hydrological, recreational, socio-economic and educational values, still they are facing severe anthropogenic pressure in the form of habitat destruction, pollution, overexploitation of resources and the invasion of alien species. India is bestowed with several natural and man-made wetlands which support rich aquatic biodiversity with high degree of endemism, especially fish diversity. Zoological Survey of India reported that, inland wetlands alone support 1027 species of fishes with more biological, nutritional and economic values. However, for the past three centuries Indian wetlands are witnessing continuous introduction of exotic fishes. According to available reports, 31 aquaculture species, 600 ornamental varieties and 2 species of larvicidal fish have been introduced. Surfacing reports confirmed that among the introduced fishes nearly 55 fish species established a sustainable reproductive population in several inland wetlands (i.e. wild) including in the biodiversity hotspots. Among the 55 the National Biodiversity Authority of India has declared 14 species as invasive. Though, there are no comprehensive studies available in India about the impacts of invasive alien species on its ecosystem and food security. In addition, researchers are of the opinion that the ongoing climate change, river linking projects, Genetically Improved Farmed Tilapia (GIFT) project and ornamental trade will exacerbate the invasive issues in future. India is thus in a position to develop new robust policy and research guidelines on the exotic species issues. Cooperation among different stakeholders and common public is the need of the hour, else India will lose its unique aquatic diversity and also face huge socio-economic problems.

     

Mytilid mussels: global habitat engineers in coastal sediments

Dense beds of mussels of the family Mytilidae occur worldwide on soft-bottoms in cold and warm temperate coastal waters and have usually been considered hot spots of biodiversity. We examined intertidal mussel beds at four distant locations around the globe with the same sampling method, to find out whether this “hot spot” designation holds universally. We studied species assemblages within the matrices of byssally interconnected mussels engineered by Mytilus edulis in the North Sea, by mixed Perumytilus purpuratus and Mytilus chilensis at the southern Chilean coast, by Musculista senhousia in the Yellow Sea and by Xenostrobus inconstans at the coast of southern Australia. In all cases, species assemblages inside mussel beds were significantly different from those outside with many species being restricted to one habitat type. However, species richness and diversity were not generally higher in mussel beds than in ambient sediments without mussels. In the North Sea (M. edulis) and at the Chilean coast (P. purpuratus, M. chilensis), mussel beds have markedly higher species numbers and diversities than surrounding sediments, but this was not the case for mussel beds in Australia (X. inconstans) and the Yellow Sea (M. senhousia) where numbers of associated species were only slightly higher and somewhat lower than in adjacent sediments, respectively. In conclusion, although soft bottom mytilid mussels generally enhance habitat heterogeneity and species diversity at the ecosystem level, mussel beds themselves are not universal centres of biodiversity, but the effects on associated species are site specific.     

Is <Emphasis Type="Italic">Gammarus tigrinus</Emphasis> (Crustacea,Amphipoda) becoming cosmopolitan through shipping? Predicting its potential invasive range using ecological niche modeling

While the intensity of global shipping has increased dramatically over the last decades, species exchange between continents has likewise intensified. Ballast water of ships is recognized playing a major role in this process. Many of the larger sea ports have become bridgeheads for invasions. Ecological niche modeling is used to investigate the potential invasive range and high invasive risk ports of the North American amphipod Gammarus tigrinus. Sixty-two occurrences of G. tigrinus in its native range (North America) and 34 environmental data sets were compiled. Data on dispersal distances were used via ecological niche modeling to analyze the invasive potential of G. tigrinus. The invasive risk of large ports was analyzed according to modeling result, as well as their salinity in the main oceanic routes of the world. G. tigrinus had a rapid range extension on the British Isles and in the rest of Western Europe. Now it is invading the countries surrounding the Baltic Sea. Worldwide it has a vast potential invasive range. It has a high invasive risk for many large ports along the main oceanic routes, among which the ports of Shanghai, Buenos Aires and Montevideo have the highest invasive risk. G. tigrinus may become cosmopolitan through shipping, and this possibility is increasing. Particular emphasis should be placed on preventing human-mediated dispersal. Ports may be the first places G. tigrinus invades. This study can identify high invasive risk ports, especially those at risk of introduced North America species. More importantly, the water of large ports should be monitored regularly for exotic aquatic organisms that may survive temporarily or permanently.     

Return of the native facilitated by the invasive? Population composition,substrate preferences and epibenthic species richness of a recently discovered shellfish reef with native European flat oysters (Ostrea edulis) in the North Sea

After being ecologically extinct for almost a century, the discovery of a shellfish reef with native European flat oysters (Ostrea edulis) in the Dutch coastal area of the North Sea by the authors of this study called for an extensive survey to better understand some of the key requirements for the return of the native oyster in coastal waters. We assessed habitat conditions, its potential for increasing biodiversity, and the role of substrate provision by other bivalves such as the invasive alien Pacific oyster (Crassostrea gigas). Using underwater visual census, O. edulis size-frequency distributions and attachment substrate was investigated, as well as the composition of the epibenthic community and substrata types inside quadrats that were distributed across the reef. This reef was found to be composed of native European flat oysters, invasive alien Pacific oysters and blue mussels (Mytilus edulis), alternated with sandy patches. The O. edulis population (6.8?±?0.6 oysters m^?2) consisted of individuals of different size classes. In quadrats with native and non-native oysters the number of epibenthic species was 60% higher compared to adjacent sand patches within the reef. Notably, our results showed that the native oyster predominantly used shell (fragments) of the invasive Pacific oyster as settlement substrate (81% of individuals). Our results optimistically show that conditions for native oyster restoration can be suitable at a local scale in the coastal North Sea area and suggest that the return of native oysters may be facilitated by novel substrate provided by invasive oysters at sites where their distribution overlap.     

Invasion ecology of quagga mussels (<Emphasis Type="Italic">Dreissena rostriformis bugensis</Emphasis>): a review of evolutionary and phylogenetic impacts

Two invasive freshwater mussels, Dreissena rostriformis bugensis (quagga mussel) and D. polymorpha (zebra mussel), reveal differences in patterns and timing of their invasions in Europe. They belong to different clades in Dreissena phylogenetics: D. rostriformis bugensis genetically is coupled with the brackish water, lacustrine D. r. distincta and the two are believed to represent a single species. As such, the guaqqa mussel has environmental requirements that differ from the congeneric D. polymorpha. D. rostriformis bugensis invasions were confined to reservoirs of the Dnieper, Don and Dniester Rivers of the Black Sea basin. We recorded D. r. bugensis outside the Black Sea basin for the first time between 1992 and 2001, along the Volga River reservoir cascade including the Northern Caspian Sea shallows. This represents a 40-year invasion time lag since an invasion corridor through the Volgo-Don Waterway was established in 1952 (a corridor used extensively by many invertebrate species from the Black Sea region). We attribute the postponed invasion of Europe by D. r. bugensis, including peculiarities in establishment and its absence in fossil records, to its phylogenetically close relationship with D. r. distincta and its recent evolutionary origin. The relatively rapid range expansion of D. r. bugensis in eastern Europe during the past several decades was facilitated by human-mediated ecosystem transformation, notably impoundment of large eastern European rivers, that have allowed this species to utilize newly transformed ecosystems.     

An invasive crab alters interaction webs in a marine community

Over the last decade, the non-native, filter-feeding crab Petrolisthes armatus invaded oyster reefs of the South Atlantic Bight at densities of thousands m⁻². Mesocosm and field experiments demonstrated that P. armatus at ∼10–75% of mean summer densities: (1) suppressed growth of small oysters, biomass of benthic microalgae, and recruitment of native mud crabs, (2) enhanced oyster, mussel, and total bivalve recruitment, macroalgal cover, and survivorship of predatory oyster drills, but (3) did not affect native taxonomic richness. Laboratory feeding assays, field tethering experiments, and population changes in field and mesocosm experiments suggest that P. armatus is a preferred prey for native mud crabs and other consumers, thus relieving predation on native species and enhancing recruitment or survival of bivalves and oyster drills. In contrast, the invasive crab can consume crustacean larvae and via this feeding may suppress recruitment of native mud crabs. Our findings should be conservative given the low densities of P. armatus seeded into experimental plots and our inability to run longer-term experiments due to controls rapidly being colonized by non-native crabs recruiting from the plankton. Invasive crabs commonly impact native communities via predation, but community impacts of this invasive crab may be as much due to its role as a preferred prey of native consumers as to its predation on native prey. Given that oysters are foundation species for shallow reefs in the South Atlantic Bight, the long-term effects of this invasion could be considerable.