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- Lövei, G.L., Lewinsohn, T.M., and Biological Invasions in Megadiverse Regions Network. Megadiverse developing countries face huge risks from invasives. Trends in Ecology and Evolution 27(1): 2-3, 2012.
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- Haydar, D. What is natural? The scale of cryptogenesis in the North Atlantic Ocean. Diversity and Distributions 18(2): 101-110, 2012.
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Aim Cryptogenic species may include those taxa that were historically introduced and are now falsely viewed as native. Investigated here is the scale of cryptogenesis in the North Atlantic Ocean by examining disjunct distributions, defined as temperate species occurring only on both sides of the North Atlantic. Disjunct distributions can be explained by four scenarios: glacial relicts, taxonomic artefacts, natural trans-oceanic dispersal and human-mediated introduction. Location North Atlantic Ocean. Methods Model taxa included ascidians, bivalves and hydrozoans. Biogeographic status (native, introduced or cryptogenic) was assigned to all species exhibiting a disjunct distribution, based upon multiple criteria. Results Of 1030 species, 60 have a strictly disjunct distribution. Of these disjunct species, for five species there is no reason to doubt their native status, and 55 species are cryptogenic or introduced. Groups with high relative dispersal capacities do not have disjunct distributions more often. Infaunal bivalves have the lowest relative number of disjunct species; none are cryptogenic or naturally disjunct. This supports the concept that glaciations are unlikely to cause disjunct distributions: there are no studies that provide conclusive evidence for the glacial relict model. Hydrozoa have the highest relative number of disjunct species, which, while historically explained by undocumented rafting, may more likely be the result of dispersal by ships, which travel relatively fast, are independent of currents and provide greater surface area. Main conclusions This reanalysis of the historical biogeography of the North Atlantic marine biota reveals that far more species may have been introduced than previously recognized, potentially significantly altering our fundamental understanding of community evolution and ecology. Species that have been present for centuries and can be important ecological engineers who have shaped contemporary communities are possibly falsely viewed as native: they may in fact be the unrecognized introductions of historical times.
- Blakeslee, A.M.H., Altman, I., Miller, A.W., Byers, J.E., Hamer, C.E., and Ruiz, G.M. Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges. Journal of Biogeography 39(3): 609-622, 2012.
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Aim To use a comparative approach to understand parasite demographic patterns in native versus introduced populations, evaluating the potential roles of host invasion history and parasite life history. Location North American east and west coasts with a focus on San Francisco Bay (SFB). Methods Species richness and prevalence of trematode parasites were examined in the native and introduced ranges of two gastropod host species, Ilyanassa obsoleta and Littorina saxatilis. We divided the native range into the putative source area for introduction and areas to the north and south; we also sampled the overlapping introduced range in SFB. We dissected 14,781 snails from 103 populations and recorded the prevalence and identity of trematode parasites. We compared trematode species richness and prevalence across the hosts' introduced and native ranges, and evaluated the influence of host availability on observed patterns. Results Relative to the native range, both I. obsoleta and L. saxatilis have escaped (lost) parasites in SFB, and L. saxatilis demonstrated a greater reduction of trematode diversity and infection prevalence than I. obsoleta. This was not due to sampling inequalities between the hosts. Instead, rarefaction curves suggested complete capture of trematode species in native source and SFB subregions, except for L. saxatilis in SFB, where infection was extremely rare. For I. obsoleta, infection prevalence of trematodes using fish definitive hosts was significantly lower in SFB compared to the native range, unlike those using bird hosts. Host availability partly explained the presence of introduced trematodes in SFB. Main conclusions Differential losses of parasite richness and prevalence for the two gastropod host species in their introduced range is probably the result of several mechanistic factors: time since introduction, propagule pressure, vector of introduction, and host availability. Moreover, the recent occurrence of L. saxatilis' invasion and its active introduction vector suggest that its parasite diversity and distribution will probably increase over time. Our study suggests that host invasion history and parasite life history play key roles in the extent and diversity of trematodes transferred to introduced populations. Our results also provide vital information for understanding community-level influences of parasite introductions, as well as for disease ecology in general.
- Perkins, L.B., Leger, E.A., and Nowak, R.S. Invasion triangle: an organizational framework for species invasion. Ecology and Evolution 1(4): 610-625, 2011.
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Species invasion is a complex, multifactor process. To encapsulate this complexity into an intuitively appealing, simple, and straightforward manner, we present an organizational framework in the form of an invasion triangle. The invasion triangle is an adaptation of the disease triangle used by plant pathologists to help envision and evaluate interactions among a host, a pathogen, and an environment. Our modification of this framework for invasive species incorporates the major processes that result in invasion as the three sides of the triangle: (1) attributes of the potential invader; (2) biotic characteristics of a potentially invaded site; and (3) environmental conditions of the site. The invasion triangle also includes the impact of external influences on each side of the triangle, such as climate and land use change. This paper introduces the invasion triangle, discusses how accepted invasion hypotheses are integrated in this framework, describes how the invasion triangle can be used to focus research and management, and provides examples of application. The framework provided by the invasion triangle is easy to use by both researchers and managers and also applicable at any level of data intensity, from expert opinion to highly controlled experiments. The organizational framework provided by the invasion triangle is beneficial for understanding and predicting why species are invasive in specific environments, for identifying knowledge gaps, for facilitating communication, and for directing management in regard to invasive species.
- Canning-Clode, J., Fowler, A.E., Byers, J.E., Carlton, J.T., and Ruiz, G.M. 'Caribbean Creep' chills out: climate change and marine invasive species. PLoS ONE 6(12): art. e29657, 2011.
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Background New marine invasions have been recorded in increasing numbers along the world's coasts due in part to the warming of the oceans and the ability of many invasive marine species to tolerate a broader thermal range than native species. Several marine invertebrate species have invaded the U.S. southern and mid-Atlantic coast from the Caribbean and this poleward range expansion has been termed 'Caribbean Creep'. While models have predicted the continued decline of global biodiversity over the next 100 years due to global climate change, few studies have examined the episodic impacts of prolonged cold events that could impact species range expansions. Methodology/Principal Findings A pronounced cold spell occurred in January 2010 in the U.S. southern and mid-Atlantic coast and resulted in the mortality of several terrestrial and marine species. To experimentally test whether cold-water temperatures may have caused the disappearance of one species of the 'Caribbean Creep' we exposed the non-native crab Petrolisthes armatus to different thermal treatments that mimicked abnormal and severe winter temperatures. Our findings indicate that Petrolisthes armatus cannot tolerate prolonged and extreme cold temperatures (4–6°C) and suggest that aperiodic cold winters may be a critical 'reset' mechanism that will limit the range expansion of other 'Caribbean Creep' species. Conclusions/Significance We suggest that temperature 'aberrations' such as 'cold snaps' are an important and overlooked part of climate change. These climate fluctuations should be accounted for in future studies and models, particularly with reference to introduced subtropical and tropical species and predictions of both rates of invasion and rates of unidirectional geographic expansion.
- Drouin, A., McKindsey, C.W., and Johnson, L.E. Detecting the impacts of notorious invaders: experiments versus observations in the invasion of eelgrass meadows by the green seaweed Codium fragile. Oecologia 168(2): 491-502, 2012.
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Biological invasions can vary in the extent of their effects on indigenous communities but predicting impacts for particular systems remains difficult. In coastal marine ecosystems, the green seaweed Codium fragile ssp. fragile is a notorious invader with its reputation based on studies conducted largely on rocky shores. The green seaweed has recently invaded soft-bottom eelgrass communities by attaching epiphytically to eelgrass (Zostera marina) rhizomes, thereby creating the potential for disruption of these coastal habitats through competition or disturbance. We investigated the effect of this invader on various aspects of eelgrass performance (shoot density and length, shoot growth, above- and below-ground biomass, carbohydrate storage) using both small-scale manipulative and large-scale observational experiments. Manipulative experiments that varied Codium abundance demonstrated clear negative effects over a 4-month period on shoot density and carbohydrate reserves, but only for high, but realistic, Codium biomass levels. Light levels were much lower under canopies for high and medium density Codium treatments relative to low and control Codium cover treatments, suggesting that shading may influence eelgrass growing under the algal cover. In contrast, these effects were either not detectable or very weak when examined correlatively with field surveys conducted at larger spatial scales, even for sites that had been invaded for over 4 years. It is premature to extend generalizations of Codium's impact derived from studies in other systems to eelgrass communities; further efforts are required to assess the long-term threats that the alga poses to this ecosystem. This study demonstrates the need to investigate impacts of invasions over multiple scales, especially those that incorporate the temporal and spatial heterogeneity of the invader's abundance.
- Chapple, D.G., Simmonds, S.M., and Wong, B.B.M. Can behavioral and personality traits influence the success of unintentional species introductions? Trends in Ecology and Evolution 27(1): 57-64, 2012.
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Unintentional species invasions are instigated by human-mediated dispersal of individuals beyond their native range. Although most introductions fail at the first hurdle, a select subset pass through each stage of the introduction process (i.e. transport, introduction, establishment and spread) to become successful invaders. Efforts to identify the traits associated with invasion success have predominately focused on deliberate introductions, which essentially bypass the initial introduction stage. Here, we highlight how behavior influences the success or failure of unintentional species introductions across each stage of the introduction process, with a particular focus on transportation and initial establishment. In addition, we emphasize how recent advances in understanding of animal personalities and individual-level behavioral variation can help elucidate the mechanisms underlying the success of stowaways.
- Weis, J.S. Invasion and predation in aquatic ecosystems. Current Zoology 57(5): 613-624, 2011.
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This article reviews biological invasions in which predation (or its absence) plays a major role in the success of the invader. Examples are described in which the invader out-competes native species for the same food, and cases in which the invader consumes valued native species. In many instances, better predator avoidance by the invasive species or the absence of predators in the new habitat contributes to the success of the invaders; in other cases native or introduced predators appear to be able to keep the invasive species in check. A relatively new management approach in the US is the idea of adding another trophic level – to have humans act as the predators and consume the invasive species. This approach is being utilized in Florida and throughout the Caribbean against the lionfish, but could be extended to other fishes, as well as to various invasive crustaceans and mollusks. This idea is controversial, and current regulations prohibiting the possession of individuals of the invasive species (e.g., mitten crabs or snakefish) would preclude the development of a fishery for them.
- Jones, E.I. and Gomulkiewicz, R. Biotic interactions, rapid evolution, and the establishment of introduced species. American Naturalist 179(2): E28-E36, 2012.
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The biotic environment can pose a challenge to introduced species; however, it is not known how rapid evolution in introduced and resident species influences the probability that the introduced species will become established. Here, we analyze the establishment phase of invasion with eco-evolutionary models of introduced species involved in predator-prey, mutualistic, or competitive interactions with a resident species. We find that, depending on the strength of the biotic interaction, establishment is impossible, guaranteed, or, in a narrow range, determined by genetic variation. Over this narrow range, rapid evolution of the introduced species always favors establishment, whereas resident evolution may either inhibit or facilitate establishment, depending on the interaction type. Coevolution can also either increase or decrease the chance of establishment, depending on the initial genotype frequencies as well as the interaction type. Our results suggest that the conditions under which genetic variation influences establishment success are limited, but they highlight the importance of considering the resident community's evolutionary response to introduced species as a component of its invasibility.
- Webber, B.L. and Scott, J.K. Rapid global change: implications for defining natives and aliens. Global Ecology and Biogeography 21(3): 305-311, 2012.
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The ability to ascribe native or alien status to species in a rapidly changing world underpins diverse research fields that overlap with global change and biological invasions via biodiversity. Current definitions generally link alien status to anthropogenic dispersal events, but this can create conflicts for active management and global change adaptation strategies, such as managed relocation and restoration ecology. Here we propose a unifying approach that allows for the incorporation of rapid global change into biological invasion terminology. We introduce the concept of a projected dispersal envelope (PDE) to define the region where a species is or could be native, irrespective of human involvement. The PDE integrates biogeography and niche theory with existing invasion terminology to place a spatial and temporal context on species movements. We draw on a diverse suite of topical organism movements to illustrate these concepts. Our restructured definitions allow for native species to move into or with rapidly shifting climatic regions, as well as identifying the inappropriate introduction of alien species to new areas. Moreover, our definitions framework forms a timely and essential component of adaptation policies and responses for invasive species management and the enhancement of biodiversity in a rapidly changing world.
- Jud, Z.R., Layman, C.A., Lee, J.A., and Arrington, D.A. Recent invasion of a Florida (USA) estuarine system by lionfish Pterois volitans / P. miles. Aquatic Biology 13(1): 21-26, 2011.
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The invasion by lionfish Pterois volitans and P. miles throughout the western Atlantic and Caribbean is emerging as a serious ecological problem. While lionfish have been identified on coral reefs and in other marine systems, additional ecosystems may be affected as the invasion spreads. Here we identify the first estuarine intrusion by lionfish in their invasive range. Lionfish (n = 211) were captured in the Loxahatchee River estuary (Florida, USA) between August 2010 and April 2011, with some individuals located as far as ~5.5 km from the ocean. Multiple size classes were documented (standard lengths ranged from 23 to 185 mm), and post-settlement juveniles were present throughout the sampling period. All individuals were found in close association with anthropogenically created habitats (e.g. docks, sea walls, submerged debris), suggesting that human-driven changes in habitat availability may facilitate estuarine invasion. Fifteen prey taxa were found in lionfish stomachs, with diets dominated by small shrimp. Since estuaries are already highly threatened by human impacts, and provide critical habitat for numerous commercially, recreationally, and ecologically important species, establishment of lionfish in these ecosystems is of particular concern.
- Hasselman, D.J., Hinrichsen, R.A., Shields, B.A., and Ebbesmeyer, C.C. The rapid establishment, dispersal, and increased abundance of invasive American shad in the Pacific Northwest. Fisheries 37(3): 103-114, 2012.
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American shad (Alosa sapidissima) were repeatedly introduced into two Pacific coastal rivers in the late 1800s. They rapidly established, dispersed, and expanded their range over 5,000 km of coastline from Mexico to Russia. American shad also increased dramatically in abundance and now comprise the largest spawning run of anadromous fish in the Columbia River (>4 million fish annually). Despite constituting a remarkable biological invasion, invasive shad have not been the subject of much scientific investigation and remain relatively obscure in the Pacific Northwest. In this first of two complementary articles, we attempt to raise the profile of invasive American shad among fisheries professionals and generate scientific interest in this biological invasion. We provide an overview of the history of their introduction and discuss the mechanisms that may have contributed to the species' establishment, rapid dispersal along the Pacific coast, and its increased abundance in the Columbia River. In the second accompanying article we discuss the possible ecological consequences of the invasion in Pacific coastal ecosystems but also its inherent value to studies of ecology and evolution. These articles are designed to be read in succession.
- Hasselman, D.J., Hinrichsen, R.A., Shields, B.A., and Ebbesmeyer, C.C. American shad of the Pacific coast: a harmful invasive species or benign introduction? Fisheries 37(3): 115-122, 2012.
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Research on the ecological effects of aquatic invasive species in North America has largely focused on the Laurentian Great Lakes, with less attention directed to their influence in coastal ecosystems. American shad (Alosa sapidissima) were introduced to the Pacific coast in the late 1800s, rapidly established, dispersed, and became prolific. Despite constituting a remarkable biological invasion, shad in their introduced range have not been the subject of much scientific investigation. The species persists in relative obscurity in the Pacific Northwest and remains ecological overlooked and evolutionarily underappreciated. In this second of two complementary articles, we consider the potential ecological effects of invasive American shad on Pacific coastal ecosystems and the possible consequences for the persistence of native salmonids. We also reflect on the intrinsic value that this invasion provides to studies of ecology and evolution and highlight several areas of research that require immediate investigation if we are to determine whether nonindigenous shad constitute a harmful invasive species or a benign introduction.
- Kruse, I., Hare, M., and Hines, A. Genetic relationships of the marine invasive crab parasite Loxothylacus panopaei: an analysis of DNA sequence variation, host specificity, and distributional range. Biological Invasions 14(3): 701-715, 2012.
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Host specificity is a key variable of the niche breath of parasites that can be an important determinant of a parasite's ability to invade new areas. There is increasing evidence that many parasite species may comprise a variety of genetically variable lineages, which differ in host specificity and geographic range. In this study, we (1) explored the extent of diversity in the invasive parasitic barnacle Loxothylacus panopaei (Rhizocephala) infecting mud crabs (2) examined the geographic origin for the invasive lineage and (3) assessed if further southward spread of the parasite may be impeded. Along the US Atlantic coast, L. panopaei infects different hosts in its invaded range (Chesapeake Bay to north of Cape Canaveral) compared to one portion of the native range in Southeast Florida. This difference was reflected in genetic lineages on two independent loci, mitochondrial cytochrome oxidase I and nuclear cytochrome c. Both loci were concordant in that they showed one lineage infecting crabs of the genus Panopeus in the native range and one lineage infecting Eurypanopeus depressus and Rhithropanopeus harrisii hosts in the invaded range and in the Gulf of Mexico , thus indicating Gulf of Mexico populations as the most likely source of introduction into Chesapeake Bay. Interestingly, the nuclear marker resolved an additional lineage of parasites infecting panopeid hosts in the native range. All three parasite lineages were well supported, but a decision about species status must await further analyses. Since its introduction in the 1960s, the invasive L. panopaei lineage has expanded its range southward along the US Atlantic coast, now almost reaching the northern limit of native Panopeus-infecting lineages at Cape Canaveral, Florida. We hypothesized that parasite-free E. depressus in Southeast Florida, living in sympatry with infected panopeid populations, might be resistant to infection by the invasive lineage. Our infection experiments rejected this hypothesis, suggesting that any impediment to further southward range expansion might be expected from temperature regimes of the subtropical zoogeographic region south of Cape Canaveral.
- Mach, M., Levings, C., McDonald, P., and Chan, K. An Atlantic infaunal engineer is established in the Northeast Pacific: Clymenella torquata (Polychaeta: Maldanidae) on the British Columbia and Washington coasts. Biological Invasions 14(3): 503-507, 2012.
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The Northwest Atlantic bamboo worm Clymenella torquata, believed to have been imported with commercial oyster culture, was last formally reported from the American Pacific coast more than 30 years ago from a single location. We report here that it is broadly distributed in British Columbia and is now established in Washington. In Samish Bay, Washington, this tubiculous infaunal worm creates a spongy, porous substrate that has proved detrimental to commercial oyster farms by causing the oysters to sink into the sediment and suffocate. Little is known about the ecological or economic impacts of this invasion in the Pacific Northwest.
- Toledo-Guedes, K., Sanchez-Jerez, P., Mora-Vidal, J., Girard, D., and Brito, A. Escaped introduced sea bass (Dicentrarchus labrax) infected by Sphaerospora testicularis (Myxozoa) reach maturity in coastal habitats off Canary Islands. Marine Ecology 33(1): 26-31, 2012.
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Aquaculture activities have introduced European sea bass (Dicentrarchus labrax) along the coasts of some of the Canary Islands. We present the first record of simultaneous male and female gonad maturation of escaped sea bass in the wild, indicating that this species is finding its essential fish habitat (EFH). Individuals with ripe gonads were only caught during January and February 2009, although the maturation and spawning season may last from November to February in the studied area (Tenerife island). Bass infected by Sphaerospora testicularis were found and the incidence of the parasite was checked. This represents the southernmost record of the parasite, probably introduced together with sea bass stock. The results are discussed from the point of view of risk assessment and the ecology of invasions being valuable for aquaculture management in Central North Atlantic and Mediterranean areas.
- Hernández, J., Stedt, J., Bonnedahl, J., Molin, Y., Drobni, M., Calisto-Ulloa, N., Gomez-Fuentes, C., Astorga-España, M.S., Gonzáez-Acuña, D., Waldenström, J., Blomqvist, M., and Olsen, B. Human-associated extended-spectrum β-lactamase in the Antarctic. Applied and Environmental Microbiology 78(6): 2056-2058, 2012.
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Escherichia coli bacteria with extended-spectrum β-actamase (ESBL) type CTX-M resistance were isolated from water samples collected close to research stations in Antarctica. The isolates had blaCTX-M-1 and blaCTX-M-15 genotypes and sequence types (ST) indicative of a human-associated origin. This is the first record of ESBL-producing enterobacteria from Antarctica.
- Haska, C.L., Yarish, C., Kraemer, G., Blaschik, N., Whitlatch, R., Zhang, H., and Lin, S. Bait worm packaging as a potential vector of invasive species. Biological Invasions 14(2): 481-493, 2012.
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Invasive species have become an increasingly greater concern for the ecological health of coastal ecosystems, yet vectors of these introductions often are unclear. This project evaluated the potential for the brown seaweed Ascophyllum nodosum ecad scorpiodes (Hauck) Reinke, packaged with bait worms (Nereis virens) harvested from the coast of Maine (USA), as a vector of invasive marine fauna and flora. Often, the seaweed and contents of the bait boxes are discarded into the water by recreational fishermen after using the bait worms, and any included non-native species may then be introduced. Bait boxes were purchased from several commercial vendors in Connecticut and New York over a two-year period. Subsamples of the seaweed were placed in laboratory culture and the growth of associated macro- and microalgae was monitored. Marine invertebrate species present in the samples were also identified and quantified. Results indicated 13 species of macroalgae and 23 species of invertebrates were associated with baitboxes. Among the highly diverse microbial assemblage detected, two species of potentially toxic marine microalgae, Alexandrium fundyense Balech and Pseudonitzschia multiseries (Hasle) Hasle, were found both prior to and after incubation at various temperatures, indicating these harmful algae are brought to and can survive in receiving waters. These findings highlight the need to consider alternative choices of bait box packaging materials or appropriate disposal methods of the seaweed in order to minimize the transport of species which are not native to the receiving coastal waters.
- Côté, I.M. and Green, S.J. Potential effects of climate change on a marine invasion: The importance of current context. Current Zoology 58(1): 1-8, 2012.
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Species invasions threaten marine biodiversity globally. There is a concern that climate change is exacerbating this problem. Here, we examined some of the potential effects of warming water temperatures on the invasion of Western Atlantic habitats by a marine predator, the Indo-Pacific lionfish (Pterois volitans and P. miles). We focussed on two temperature-dependent aspects of lionfish life-history and behaviour: pelagic larval duration, because of its link to dispersal potential, and prey consumption rate, because it is an important determinant of the impacts of lionfish on native prey. Using models derived from fundamental metabolic theory, we predict that the length of time spent by lionfish in the plankton in early life should decrease with warming temperatures, with a concomitant reduction in potential dispersal distance. Although the uncertainty around change in dispersal distances is large, predicted reductions are, on average, more than an order of magnitude smaller than the current rate of range expansion of lionfish in the Caribbean. Nevertheless, because shorter pelagic larval duration has the potential to increase local retention of larvae, local lionfish management will become increasingly important under projected climate change. Increasing temperature is also expected to worsen the current imbalance between rates of prey consumption by lionfish and biomass production by their prey, leading to a heightened decline in native reef fish biomass. However, the magnitude of climate-induced decline is predicted to be minor compared to the effect of current rates of lionfish population increases (and hence overall prey consumption rates) on invaded reefs. Placing the predicted effects of climate change in the current context thus reveals that, at least for the lionfish invasion, the threat is clear and present, rather than future.
- Hufbauer, R.A., Facon, B., Ravigné, V., Turgeon, J., Foucaud, J., Lee, C.E., Rey, O., and Estoup, A. Anthropogenically induced adaptation to invade (AIAI): contemporary adaptation to human-altered habitats within the native range can promote invasions. Evolutionary Applications 5(1): 89-101, 2012.
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Adaptive evolution is currently accepted as playing a significant role in biological invasions. Adaptations relevant to invasions are typically thought to occur either recently within the introduced range, as an evolutionary response to novel selection regimes, or within the native range, because of long-term adaptation to the local environment. We propose that recent adaptation within the native range, in particular adaptations to human-altered habitat, could also contribute to the evolution of invasive populations. Populations adapted to human-altered habitats in the native range are likely to increase in abundance within areas frequented by humans and associated with human transport mechanisms, thus enhancing the likelihood of transport to a novel range. Given that habitats are altered by humans in similar ways worldwide, as evidenced by global environmental homogenization, propagules from populations adapted to human-altered habitats in the native range should perform well within similarly human-altered habitats in the novel range. We label this scenario 'Anthropogenically Induced Adaptation to Invade'. We illustrate how it differs from other evolutionary processes that may occur during invasions, and how it can help explain accelerating rates of invasions.
- Repetto, M. and Griffen, B.D. Physiological consequences of parasite infection in the burrowing mud shrimp, Upogebia pugettensis, a widespread ecosystem engineer. Marine and Freshwater Research 63(1): 60-67, 2012.
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The burrowing mud shrimp, Upogebia pugettensis, is an important ecosystem engineer throughout bays and estuaries along the Pacific coast of North America. Populations of U. pugettensis have recently declined throughout its range. A likely reason for this decline is the arrival of an invasive bopyrid isopod parasite, Orthione griffenis, which has colonised the system and increased in prevalence. We tested the following three hypotheses regarding this host-parasite system: (1) parasite infection is correlated with the volume of water processed by the host; (2) infection negatively affects host's energetic state; and (3) infection causes feminisation in male hosts. We used several physiological and morphological measures to quantify the effects of this parasite infection on U. pugettensis. The parasite appears to have different physiological effects on male and female hosts. Our study provides mixed support for the previous theory that predicted the mechanistic interactions between this host and its new parasite. Recent examples from other systems have demonstrated that invasive parasites can have far-reaching influences when they infect ecosystem engineers. Given the negative effects of O. griffenis on U. pugettensis, this invasive parasite may have similarly large impacts on Pacific North-west estuaries throughout its invaded range.
- Norkko, J., Reed, D.C., Timmermann, K., Norkko, A., Gustafsson, B.G., Bonsdorff, E., Slomp, C.P., Carstensen, J., and Conley, D.J. A welcome can of worms? Hypoxia mitigation by an invasive species. Global Change Biology 18(2): 422-434, 2012.
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Invasive species and bottom-water hypoxia both constitute major global threats to the diversity and integrity of marine ecosystems. These stressors may interact with unexpected consequences, as invasive species that require an initial environmental disturbance to become established can subsequently become important drivers of ecological change. There is recent evidence that improved bottom-water oxygen conditions in coastal areas of the northern Baltic Sea coincide with increased abundances of the invasive polychaetes Marenzelleria spp. Using a reactive-transport model, we demonstrate that the long-term bioirrigation activities of dense Marenzelleria populations have a major impact on sedimentary phosphorus dynamics. This may facilitate the switch from a seasonally hypoxic system back to a normoxic system by reducing the potential for sediment-induced eutrophication in the upper water column. In contrast to short-term laboratory experiments, our simulations, which cover a 10-year period, show that Marenzelleria has the potential to enhance long-term phosphorus retention in muddy sediments. Over time bioirrigation leads to a substantial increase in the iron-bound phosphorus content of sediments while reducing the concentration of labile organic carbon. As surface sediments are maintained oxic, iron oxyhydroxides are able to persist and age into more refractory forms. The model illustrates mechanisms through which Marenzelleria can act as a driver of ecological change, although hypoxic disturbance or natural population declines in native species may be needed for them to initially become established. Invasive species are generally considered to have a negative impact; however, we show here that one of the main recent invaders in the Baltic Sea may provide important ecosystem services. This may be of particular importance in low-diversity systems, where disturbances may dramatically alter ecosystem services due to low functional redundancy. Thus, an environmental problem in one region may be either exacerbated or alleviated by a single species from another region, with potentially ecosystem-wide consequences.
- Terlizzi, A., Felline, S., Lionetto, M.G., Caricato, R., Perfetti, V., Cutignano, A., and Mollo, E. Detrimental physiological effects of the invasive alga Caulerpa racemosa on the Mediterranean white seabream Diplodus sargus. Aquatic Biology 12(2): 109-117, 2011.
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Observational data suggest that the white seabream Diplodus sargus, a sparid fish of economic and ecological relevance in the Mediterranean Sea, has included the invasive green alga Caulerpa racemosa in its diet. Here we adopted a chemoecological approach to study the trophic relationship between the fish and the exotic pest. We demonstrated that the red pigment caulerpin, the most abundant secondary metabolite of C. racemosa, enters food chains and accumulates in the fish tissues. General biological condition markers associated with fish health and reproductive development were measured and correlated with the caulerpin levels in the fish tissues. Significant correlations among caulerpin tissue load (determined by liquid chromatography-mass spectrometry analysis) and fish condition factor and hepatosomatic index were obtained, suggesting a possible detrimental effect of the dietary exposure to C. racemosa on D. sargus. Glutathione peroxidase and catalase activity were also significantly correlated with caulerpin concentrations in the liver, suggesting a possible interaction between algal metabolites and liver antioxidant mechanisms. Studies on the impact of invasive macroalgae on marine assemblages have been almost exclusively focused on the structural modification of benthic assemblages, through the alteration of the relative importance of some endemic species and the modification of habitat complexity. Here we propose a new mechanism by which invasive algae can impact marine systems, namely the entry of pest metabolites in food webs, with potential detrimental effects on the population dynamics of a single species, alteration of trophic webs and changes in the functioning of coastal ecosystems.
- Kornis, M.S., Mercado-Silva, N., and Vander Zanden, M.J. Twenty years of invasion: a review of round goby Neogobius melanostomus biology, spread and ecological implications. Journal of Fish Biology 80(2): 235-285, 2012.
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The round goby Neogobius melanostomus is one of the most wide-ranging invasive fish on earth, with substantial introduced populations within the Laurentian Great Lakes watershed, the Baltic Sea and several major European rivers. Rapid expansion and deleterious ecosystem effects have motivated extensive research on this species; here this research is synthesized. Maps of the global distribution are provided and the invasion history of N. melanostomus, which spread more rapidly at first in North America, but has undergone substantial expansion over the past decade in the Baltic Sea, is summarized. Meta-analyses comparing their size at age, diet, competitors and predators in North American and European ecosystems are provided. Size at age is region specific, with saline habitats typically supporting larger and faster growing individuals than fresh water. Neogobius melanostomus prey differs substantially between regions, demonstrating a capacity to adapt to locally abundant food sources. Neogobius melanostomus comprise at least 50% of the diet of eight taxa in at least one site or life stage; in total, 16 predator taxa are documented from the Laurentian Great Lakes v. five from Eurasia. Invasive N. melanostomus are the only common forage fish to heavily exploit mussels in the Laurentian Great Lakes and the Baltic Sea, facilitating the transfer of energy from mussels to higher trophic levels in both systems. Neogobius melanostomus morphology, life history, reproduction, habitat preferences, environmental tolerances, parasites, environmental effects, sampling strategies and management are also discussed. Neogobius melanostomus inhabit a wide range of temperate freshwater and brackish-water ecosystems and will probably continue to spread via ballast water, accidental bait release and natural dispersal worldwide. Climate change will probably enhance N. melanostomus expansion by elevating water temperatures closer to its energetic optimum of 26° C. Future research needs are presented; most pressing are evaluating the economic effects of N. melanostomus invasion, determining long-term population level effects of egg predation on game-fish recruitment and comparing several variables (density, ecological effects morphology and life history) among invaded ecosystems. This review provides a central reference as researchers continue studying N. melanostomus, often as examples for advancing basic ecology and invasion biology.
- Janiak, D.S. and Whitlatch, R.B. Epifaunal and algal assemblages associated with the native Chondrus crispus (Stackhouse) and the non-native Grateloupia turuturu (Yamada) in eastern Long Island Sound. Journal of Experimental Marine Biology and Ecology 413: 38-44, 2012.
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Although the spread of non-native algae is rapidly escalating, relatively few ecological studies have been done to gauge the impacts incurred to native flora and fauna. A reduction in the dominance of a native habitat-forming macroalga due to the replacement by an introduced species can have adverse effects on the community. The non-native red alga Grateloupia turuturu, first reported in Rhode Island, USA in 1994, has since extended its southern range into eastern Long Island Sound. This large alga has the potential to impact coastal communities by altering the floristic composition important to associated flora and fauna. A comparison of algal and epifaunal assemblages was made during 2006 and 2007 between native and non-native algal communities dominated by either G. turuturu or the native, Chondrus crispus at two sites in Long Island Sound. We found that within Grateloupia-dominated habitat, there was a large decrease in overall macrophyte biomass as compared to native habitat. We also found that habitat dominated by the non-native alga reduced species richness and total abundance of invertebrates relative to nearby habitats dominated by C. crispus. In addition, we found that the dominant mesofaunal species, important to higher trophic level consumers, had greatly reduced densities in communities dominated by the non-native alga.
- Wright, J.T., Byers, J.E., Koukoumaftsis, L.P., and Gribben, P.E. Differences in anti-predator traits of a native bivalve following invasion by a habitat-forming seaweed. Marine and Freshwater Research 63(3): 246-250, 2012.
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Invasive habitat-forming species modify important environmental factors with major consequences for associated fauna. We examined how the invasive habitat-forming seaweed Caulerpa taxifolia affects anti-predator traits of a native bivalve and found that bivalves in Caulerpa habitat have thinner, weaker shells and low resistance to opening of their valves. These trait modifications are likely to increase their susceptibility to predation.
- Keller, R.P. and Perrings, C. International policy options for reducing the environmental impacts of invasive species. BioScience 61(12): 1005-1012, 2011.
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Preventing the spread of nonnative invasive species is an international public good. Some categories of invasive species - such as diseases of humans and livestock - are addressed by international agreements that coordinate efforts to reduce their spread. In contrast, invasive species that primarily cause environmental impacts are managed almost exclusively at the national level. Control of environmental invaders is internationally undersupplied because the efforts of nations that do invest to prevent their spread are undercut by nations that do not. Addressing this problem will require international cooperation. We identify the international approach to controlling human diseases as a model that could provide institutions and mechanisms to map the spread of environmental invaders and assess the risks they impose. This would allow individual nations to manage potential vectors of invasion. Because such a system is unlikely to be implemented in the near future, we make recommendations for intermediate steps, including the widespread adoption of existing risk assessments and importation standards.
- Oidtmann, B. Review of biological factors relevant to import risk assessments for epizootic ulcerative syndrome (Aphanomyces invadans). Transboundary and Emerging Diseases 59(1): 26-39, 2012.
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Epizootic ulcerative syndrome (EUS) is a disease affecting both wild and farmed fish in freshwater and estuarine environments. After it was first described in Japan in 1971, the disease has spread widely across Asia and to some regions of Australia, North America and Africa. In Asia and Africa, the spread of the disease has substantially affected livelihoods of fish farmers and fishermen. No reports are yet published showing the presence of the disease in Europe or South America. Given its epizootic nature and its broad susceptible fish species range, it would appear that the disease has the potential for further spread. This study provides a review of the scientific literature on several biological factors of the pathogen, Aphanomyces invadans, associated with the disease EUS and aspects of the disease that are relevant to undertaking import risk assessments (IRA) covering (i) Life cycle and routes of transmission; (ii) Minimum infectious dose; (iii) Tissue localization and pathogen load; (iv) Predisposing factors for infection and factors influencing expression of disease; (v) Carrier state in fish; (vi) Diagnostic methods; (vii) Survival in the environment; (viii) Permissive temperature range; (ix) Stability of the agent in aquatic animal products; (x) Prevalence of infection; and (xi) Affected life stages. Much of the biological information presented is relevant to a broad range of risk questions. Areas where data are lacking were identified, and the information provided is put into context with other aspects that need to be addressed in an IRA.
- Morgan, E.H. and Richardson, C.A. Capricious bioinvasions versus uncoordinated management strategies: how the most unlikely invaders can prosper under the current UK legislation framework. Aquatic Conservation: Marine and Freshwater Ecosystems 22(1): 87-103, 2012.
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1. Bioinvasions are known to be highly unpredictable and context-dependent, varying both spatially and temporally, particularly in areas of intense anthropogenic activity and disturbance. Even the most unlikely invader can rapidly become problematic in the absence of frequent, coherent, and flexible management strategies. Using the recent spread of the Chilean oyster (Ostrea chilensis Philippi 1845) within a designated Special Area of Conservation, the paper describes what can happen to seemingly innocuous non-native species under the often complicated and uncoordinated current UK legislation framework. 2. Following >30 years of containment at Tal y Foel (North Wales, UK), O. chilensis, a species with a highly-reduced natural dispersal capacity, has now spread over a range of >30 km of shoreline. Alternative vectors, including rafting and several anthropogenic activities, are likely to have facilitated the dispersal of O. chilensis away from Tal y Foel. 3. Areas of high oyster densities (maximum = 232 oysters m-2) have become established both close to and distant from the site of original introduction. The presence of all year classes throughout the observed age range (≤7 and ≤9 years old in the intertidal and subtidal populations, respectively) confirms regular annual recruitment in the area. Information is now urgently required regarding the factors that promote the persistence and spread of O. chilensis within its new environment, as well as the impacts of its increasing localized dominance on the native biodiversity and ecosystem function. 4. As well as providing valuable, up-to-date information on the recent spread of this non-native species, the paper highlights discrepancies in the current UK legislation framework that allow for the successful establishment and spread of even the most unlikely invaders. The formation of a comprehensive and dedicated EU legal framework for managing invasives is advocated that also promotes coherence and continuity with impending legislative instruments concerning other relevant sectors.
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