Progress toward understanding the ecological impacts of nonnative species
TL;DR: 19 testable hypotheses that explain temporal and spatial variation in impact are identified and reviewed and highlight the importance of the functional ecology of the nonnative species and the structure, diversity, and evolutionary experience of the recipient community as general determinants of impact.
Abstract: A predictive understanding of the ecological impacts of nonnative species has been slow to develop, owing largely to an apparent dearth of clearly defined hypotheses and the lack of a broad theoretical framework. The context dependency of impact has fueled the perception that meaningful generalizations are nonexistent. Here, we identified and reviewed 19 testable hypotheses that explain temporal and spatial variation in impact. Despite poor validation of most hypotheses to date, evidence suggests that each can explain at least some impacts in some situations. Several hypotheses are broad in scope (applying to plants and animals in virtually all contexts) and some of them, intriguingly, link processes of colonization and impact. Collectively, these hypotheses highlight the importance of the functional ecology of the nonnative species and the structure, diversity, and evolutionary experience of the recipient community as general determinants of impact; thus, they could provide the foundation for a theoretical framework for understanding and predicting impact. Further substantive progress toward this goal requires explicit consideration of within-taxon and across-taxa variation in the per capita effect of invaders, and analyses of complex interactions between invaders and their biotic and abiotic environments.
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TL;DR: Elton's "The Ecology of Invasions by Animals and Plants" as mentioned in this paper is one of the most cited books on invasion biology, and it provides an accessible, engaging introduction to the most important environmental crises of our time.
Abstract: Much as Rachel Carson's \"Silent Spring\" was a call to action against the pesticides that were devastating bird populations, Charles S. Elton's classic \"The Ecology of Invasions by Animals and Plants\" sounded an early warning about an environmental catastrophe that has become all too familiar today-the invasion of nonnative species. From kudzu to zebra mussels to Asian long-horned beetles, nonnative species are colonizing new habitats around the world at an alarming rate thanks to accidental and intentional human intervention. One of the leading causes of extinctions of native animals and plants, invasive species also wreak severe economic havoc, causing $79 billion worth of damage in the United States alone. Elton explains the devastating effects that invasive species can have on local ecosystems in clear, concise language and with numerous examples. The first book on invasion biology, and still the most cited, Elton's masterpiece provides an accessible, engaging introduction to one of the most important environmental crises of our time. Charles S. Elton was one of the founders of ecology, who also established and led Oxford University's Bureau of Animal Population. His work has influenced generations of ecologists and zoologists, and his publications remain central to the literature in modern biology. \"History has caught up with Charles Elton's foresight, and \"The Ecology of Invasions\" can now be seen as one of the central scientific books of our century.\"-David Quammen, from the Foreword to \"Killer Algae: The True Tale of a Biological Invasion\
1,321 citations
TL;DR: The synthesis suggests a strong negative influence of invasive species on the abundance of aquatic communities, particularly macrophytes, zooplankton and fish, and proposes a framework of positive and negative links between invasive species at four trophic positions and the five different components of recipient communities.
Abstract: The introduction of invasive species, which often differ functionally from the components of the recipient community, generates ecological impacts that propagate along the food web. This review aims to determine how consistent the impacts of aquatic invasions are across taxa and habitats. To that end, we present a global meta-analysis from 151 publications (733 cases), covering a wide range of invaders (primary producers, filter collectors, omnivores and predators), resident aquatic community components (macrophytes, phytoplankton, zooplankton, benthic invertebrates and fish) and habitats (rivers, lakes and estuaries). Our synthesis suggests a strong negative influence of invasive species on the abundance of aquatic communities, particularly macrophytes, zooplankton and fish. In contrast, there was no general evidence for a decrease in species diversity in invaded habitats, suggesting a time lag between rapid abundance changes and local extinctions. Invaded habitats showed increased water turbidity, nitrogen and organic matter concentration, which are related to the capacity of invaders to transform habitats and increase eutrophication. The expansion of invasive macrophytes caused the largest decrease in fish abundance, the filtering activity of filter collectors depleted planktonic communities, omnivores (including both facultative and obligate herbivores) were responsible for the greatest decline in macrophyte abundance, and benthic invertebrates were most negatively affected by the introduction of new predators. These impacts were relatively consistent across habitats and experimental approaches. Based on our results, we propose a framework of positive and negative links between invasive species at four trophic positions and the five different components of recipient communities. This framework incorporates both direct biotic interactions (predation, competition, grazing) and indirect changes to the water physicochemical conditions mediated by invaders (habitat alteration). Considering the strong trophic links that characterize aquatic ecosystems, this framework is relevant to anticipate the far-reaching consequences of biological invasions on the structure and functionality of aquatic ecosystems.
686 citations
Cites background from "Progress toward understanding the e..."
...Multiple studies have highlighted that the impacts of invasive species are context-dependent, differing between species and habitats (Ricciardi & Atkinson, 2004; Ricciardi et al., 2013)....
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...This framework is also relevant for environmental practitioners, because distinguishing invaders with minor effects from those with large multilevel effects is critical for guiding management and prevention efforts (McCarthy et al., 2006; Ricciardi et al., 2013)....
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...Finally, the impacts of invasive species vary widely spatially and are highly context-dependent (Ricciardi et al., 2013)....
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Academy of Sciences of the Czech Republic1, Stellenbosch University2, Charles University in Prague3, Canterbury of New Zealand4, University of Tennessee5, University of Fribourg6, Zoological Society of London7, University College London8, Williams College9, Durham University10, University of Vienna11, South African National Parks12, International Union for Conservation of Nature and Natural Resources13, Free University of Berlin14, Leibniz Association15, Martin Luther University of Halle-Wittenberg16, Helmholtz Centre for Environmental Research - UFZ17, Czech University of Life Sciences Prague18, United States Forest Service19, University of Toronto20, University of Rhode Island21, University of Concepción22, University of Konstanz23, Taizhou University24, Spanish National Research Council25, University of Seville26, University of Pretoria27
TL;DR: Improved international cooperation is crucial to reduce the impacts of invasive alien species on biodiversity, ecosystem services, and human livelihoods, as synergies with other global changes are exacerbating current invasions and facilitating new ones, thereby escalating the extent and impacts of invaders.
Abstract: Biological invasions are a global consequence of an increasingly connected world and the rise in human population size The numbers of invasive alien species – the subset of alien species that spread widely in areas where they are not native, affecting the environment or human livelihoods – are increasing Synergies with other global changes are exacerbating current invasions and facilitating new ones, thereby escalating the extent and impacts of invaders Invasions have complex and often immense long‐term direct and indirect impacts In many cases, such impacts become apparent or problematic only when invaders are well established and have large ranges Invasive alien species break down biogeographic realms, affect native species richness and abundance, increase the risk of native species extinction, affect the genetic composition of native populations, change native animal behaviour, alter phylogenetic diversity across communities, and modify trophic networks Many invasive alien species also change ecosystem functioning and the delivery of ecosystem services by altering nutrient and contaminant cycling, hydrology, habitat structure, and disturbance regimes These biodiversity and ecosystem impacts are accelerating and will increase further in the future Scientific evidence has identified policy strategies to reduce future invasions, but these strategies are often insufficiently implemented For some nations, notably Australia and New Zealand, biosecurity has become a national priority There have been long‐term successes, such as eradication of rats and cats on increasingly large islands and biological control of weeds across continental areas However, in many countries, invasions receive little attention Improved international cooperation is crucial to reduce the impacts of invasive alien species on biodiversity, ecosystem services, and human livelihoods Countries can strengthen their biosecurity regulations to implement and enforce more effective management strategies that should also address other global changes that interact with invasions
677 citations
Cites background from "Progress toward understanding the e..."
...Research on invasion impacts has developed rapidly over the past decade (Ricciardi et al., 2013; Anton et al., 2019), yielding improved understanding of mechanisms underlying these impacts and development of a sound theoretical basis and conceptual frameworks (Jeschke et al., 2014; Kumschick et…...
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...…diversity of invaded communities and trophic networks, and alter ecosystem productivity, nutrient and contaminant cycling, hydrology, and disturbance regimes (e.g. Brooks et al., 2004; Suarez & Tsutsui, 2008; Kenis et al., 2009; Ricciardi et al., 2013; Blackburn, Bellard, & Ricciardi, 2019)....
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Zoological Society of London1, University of Vienna2, Imperial College London3, Lincoln University (New Zealand)4, Technische Universität München5, Helmholtz Centre for Environmental Research - UFZ6, Stellenbosch University7, Academy of Sciences of the Czech Republic8, Charles University in Prague9, University of Bern10, Environment Agency11, McGill University12, Spanish National Research Council13, International Union for Conservation of Nature and Natural Resources14, University of Fribourg15
TL;DR: A method for categorising and comparing alien or invasive species in terms of how damaging they are to the environment, that can be applied across all taxa, scales, and impact metrics is presented.
Abstract: Species moved by human activities beyond the limits of their native geographic ranges into areas in which they do not naturally occur (termed aliens) can cause a broad range of significant changes to recipient ecosystems; however, their impacts vary greatly across species and the ecosystems into which they are introduced. There is therefore a critical need for a standardised method to evaluate, compare, and eventually predict the magnitudes of these different impacts. Here, we propose a straightforward system for classifying alien species according to the magnitude of their environmental impacts, based on the mechanisms of impact used to code species in the International Union for Conservation of Nature (IUCN) Global Invasive Species Database, which are presented here for the first time. The classification system uses five semi-quantitative scenarios describing impacts under each mechanism to assign species to different levels of impact-ranging from Minimal to Massive-with assignment corresponding to the highest level of deleterious impact associated with any of the mechanisms. The scheme also includes categories for species that are Not Evaluated, have No Alien Population, or are Data Deficient, and a method for assigning uncertainty to all the classifications. We show how this classification system is applicable at different levels of ecological complexity and different spatial and temporal scales, and embraces existing impact metrics. In fact, the scheme is analogous to the already widely adopted and accepted Red List approach to categorising extinction risk, and so could conceivably be readily integrated with existing practices and policies in many regions.
555 citations
Cites background or methods from "Progress toward understanding the e..."
...Table S1 Guidance regarding the use of the confidence rating (modified from the EPPO pest risk assessment decision support scheme [2,64])....
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...broad range of environmental impacts, defined here as measurable changes to the properties of an ecosystem by an alien species [1,2], at different levels of organisation (Box 1)....
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...Similarly, an alien impact that is observed in one area of the introduced range may not occur elsewhere, or may not be as important elsewhere: invasiveness, and by extension impact, is a characteristic of a population rather than a species [2,47]....
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...Environmental impact: a measurable change to the properties of an ecosystem by an alien species [2]....
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01 Jul 2011
TL;DR: This article proposed a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions.
Abstract: There has been a dramatic growth in research on biological invasions over the past 20 years, but a mature understanding of the field has been hampered because invasion biologists concerned with different taxa and different environments have largely adopted different model frameworks for the invasion process, resulting in a confusing range of concepts, terms and definitions. In this review, we propose a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions. The unified framework combines previous stage-based and barrier models, and provides a terminology and categorisation for populations at different points in the invasion process.
338 citations
References
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TL;DR: Stabilizing mechanisms are essential for species coexistence and include traditional mechanisms such as resource partitioning and frequency-dependent predation, as well as mechanisms that depend on fluctuations in population densities and environmental factors in space and time.
Abstract: ▪ Abstract The focus of most ideas on diversity maintenance is species coexistence, which may be stable or unstable. Stable coexistence can be quantified by the long-term rates at which community members recover from low density. Quantification shows that coexistence mechanisms function in two major ways: They may be (a) equalizing because they tend to minimize average fitness differences between species, or (b) stabilizing because they tend to increase negative intraspecific interactions relative to negative interspecific interactions. Stabilizing mechanisms are essential for species coexistence and include traditional mechanisms such as resource partitioning and frequency-dependent predation, as well as mechanisms that depend on fluctuations in population densities and environmental factors in space and time. Equalizing mechanisms contribute to stable coexistence because they reduce large average fitness inequalities which might negate the effects of stabilizing mechanisms. Models of unstable coexitence...
5,240 citations
"Progress toward understanding the e..." refers background in this paper
...The classic competition/colonization trade-off, which allows a superior competitor and superior disperser or offspring–producer to coexist, recognizes fecundity and dispersal as the counterbalance to niche exploitation (Tilman 1997, Chesson 2000b, Mouquet et al. 2005)....
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...If native and nonnative species differ in their ability to acquire and use resources as the environment varies, then they may coexist when each species can exploit resources during favorable periods in ways that allow them to endure temporarily unfavorable periods (Chesson 2000a, b)....
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University of Texas at Austin1, University of California, Davis2, University of Montpellier3, Florida State University4, University of Chicago5, Washington University in St. Louis6, University of California, Berkeley7, University of Florida8, University of British Columbia9, University of York10, PSL Research University11, McGill University12
TL;DR: This framework is used to discuss why the metacommunity concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples.
Abstract: The metacommunity concept is an important way to think about linkages between different spatial scales in ecology. Here we review current understanding about this concept. We first investigate issues related to its definition as a set of local communities that are linked by dispersal of multiple potentially interacting species. We then identify four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone.
4,266 citations
"Progress toward understanding the e..." refers background in this paper
...Elevated fecundity can allow nonnative species to dominate a landscape, according to spatial models (e.g., mass effects in meta-community models; Leibold et al. 2004)....
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4,002 citations
TL;DR: Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense, and theories on the evolution of plant defenses are compared with other theories.
Abstract: The degree of herbivory and the effectiveness of defense varies widely among plant species. Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense. When resource are limited, plants with inherently slow growth are favored over those with fast growth rates; slow rates in turn favor large investments in antiherbivore defenses. Leaf lifetime, also determined by resource availability, affects the relative advantages of defenses with different turnover rates. Relative limitation of different resources also constrains the types of defenses. The proposals are compared with other theories on the evolution of plant defenses.
3,601 citations
"Progress toward understanding the e..." refers background in this paper
...…species perform better in the absence of their specialist predators or parasites (see Enemy release hypothesis), if they arrive in their new range without these enemies, they may divert available energy and resources (previously allocated to defenses) to growth and reproduction (Coley et al. 1985)....
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TL;DR: A new hypothesis, based on differences in the rates at which populations of competing species approach competitive equilibrium (reduction or exclusion of some species), is proposed to explain patterns of species diversity.
Abstract: A new hypothesis, based on differences in the rates at which populations of competing species approach competitive equilibrium (reduction or exclusion of some species), is proposed to explain patte...
3,266 citations
"Progress toward understanding the e..." refers background in this paper
...The dynamic equilibrium model of species diversity integrates disturbance, productivity, and competitive ability to determine rates of competitive displacement (Huston 1979)....
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...…that, for native and nonnative species alike, disturbance will cause diversity to increase in highly productive environments (by removing dominant species and allowing inferior competitors to survive) and decline in unproductive environments (where competition is limited) (Huston 1979, 1994)....
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...16) Dynamic equilibrium model Huston (1979, 2004) Disturbance, productivity, and competitive ability determine rates of competitive displacement....
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