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Conceptual path diagram predicting hypothesized direct and indirect relationships among species-level (hollow rectangles), location-level (light grey rectangles) and event-level (dark grey rectangles) factors commonly found to influence various measures of invasion success (hollow circle). Arrows indicate hypothesized causality.
Source publication
Aim
Biological invasions are driven by factors related to species, locations and events. Species‐level factors (namely functional traits) often distinguish successful invaders from other groups of species in trait‐only analyses. However, traits are routinely found to be much less important than event‐level (e.g. propagule pressure) or location‐leve...
Contexts in source publication
Context 1
... this study, we developed a conceptual hypothesis depict- ing direct and indirect relationships among the major species-, location-and event-level factors commonly found to predict various measures of invasion success of organisms (Fig. 1). We predicted that functional species traits have a direct effect on introduction/invasion success, but also an indirect effect via (1) propagule pressure, (2) native range size, and (3) climate match between the native and non- native distributions. We also hypothesized that native range size affects introduction/invasion success ...
Context 2
... a direct effect on introduction/invasion success, but also an indirect effect via (1) propagule pressure, (2) native range size, and (3) climate match between the native and non- native distributions. We also hypothesized that native range size affects introduction/invasion success indirectly by influ- encing propagule pressure and climate match (Fig. 1). We then used structural equation modelling (SEM) to evaluate our hypothesis with two independent, open-access datasets from case studies that estimated direct effects of the three main drivers of invasions (McGregor et al., 2012;Mahoney et al., 2015). In doing this, we demonstrate the importance of considering indirect effects of ...
Context 3
... explore the indirect role of functional species traits in determining invasion success, we applied our conceptual hypothesis ( Fig. 1) to two independent datasets (McGregor et al., 2012;Mahoney et al., 2015). These datasets come from studies of very different taxa at different spatial extents (global and national). We examined our conceptual hypothe- sis ( Fig. 1) using a combination of classical path analysis and SEM, which are ideal for evaluating complex a priori ...
Context 4
... indirect role of functional species traits in determining invasion success, we applied our conceptual hypothesis ( Fig. 1) to two independent datasets (McGregor et al., 2012;Mahoney et al., 2015). These datasets come from studies of very different taxa at different spatial extents (global and national). We examined our conceptual hypothe- sis ( Fig. 1) using a combination of classical path analysis and SEM, which are ideal for evaluating complex a priori hypoth- eses in which predictor variables are themselves driven by other predictor ...
Context 5
... We then used SEM to esti- mate overall fit of the path model and to prune insignifi- cant paths if necessary. Beginning with naturalization success (the terminal variable) and working backward through our conceptual path model, we used multiple regression to identify significant predictors of each variable based on our hypothesized relationships (Fig. 1). We con- ducted regressions using backward model selection, and allowed variables to remain in models at P 0.10. This lib- eral threshold ensured that variables with even marginal effects were given at least initial consideration in path anal- yses. This approach amounts to classical path analysis in which each endogenous variable ...
Citations
... This uncertainty was manifested by the occurrence of a few false positives. Factors such as species interactions, species traits, habitat suitability and human-mediated dispersal can all influence invasion outcomes (Mächler and Altermatt 2012;Peoples and Goforth 2017), and these factors may not be fully captured by the risk screening process. This demonstrates the importance of a multi-tiered approach to implementing the a priori categorization, which should be based on a combination of species-specific, global and regional databases, as well as incorporating literature searches where appropriate (Vilizzi et al. 2022a). ...
Non-native species risk analysis is a dynamic process that requires periodic review
and revision. In this study, we investigated changes in the risk ranks of the 69 non-native freshwater fish species in England and Wales previously screened with the Fish Invasiveness Screening Kit using its successor, the Aquatic Species Invasiveness Screening Kit (AS-ISK). Our objectives were to assess shifts in species risk ranks, evaluate the implications of transitioning to the AS-ISK, and integrate climate change predictions into the screenings. Re-screening revealed several changes, with eleven species re-categorized from non-invasive to invasive and one from invasive to non-invasive, and with 18 species changing their risk ranks. Climate change projections influenced outcomes, with 40 out of 41 high-risk species maintaining such status when accounting for this component. The re-screening process implemented in this study emphasizes the importance of updating protocols to incorporate new data and climate change projections for more accurate risk screening. Analysis showed varied responses to climate change among species, with implications for management strategies. Salmonids exhibited nuanced responses, suggesting the need for tailored management approaches. Confidence levels were generally medium, highlighting the importance of continual refinement. Our study underscores the necessity of regularly updating non-native species risk screenings and follow-up assessments to account for newly available literature information. By integrating new data and climate change scenarios, the effectiveness of management strategies can be enhanced with the aim of safeguarding aquatic ecosystems and their biodiversity. Further research should focus on refining the entire risk analysis process and understanding species responses to changing environmental conditions to inform proactive management approaches.
... This uncertainty was manifested by the occurrence of a few false positives. Factors such as species interactions, species traits, habitat suitability and human-mediated dispersal can all influence invasion outcomes (Mächler and Altermatt 2012;Peoples and Goforth 2017), and these factors may not be fully captured by the risk screening process. This demonstrates the importance of a multi-tiered approach to implementing the a priori categorization, which should be based on a combination of species-specific, global and regional databases, as well as incorporating literature searches where appropriate (Vilizzi et al. 2022a). ...
Non-native species risk analysis is a dynamic process that requires periodic reviewand revision. In this study, we investigated changes in the risk ranks of the 69 non-native freshwater fish species in England and Wales previously screened with the FishInvasiveness Screening Kit using its successor, the Aquatic Species InvasivenessScreening Kit (AS-ISK). Our objectives were to assess shifts in species risk ranks,evaluate the implications of transitioning to the AS-ISK, and integrate climatechange predictions into the screenings. Re-screening revealed several changes, witheleven species re-categorized from non-invasive to invasive and one from invasiveto non-invasive, and with 18 species changing their risk ranks. Climate change projections influenced outcomes, with 40 out of 41 high-risk species maintainingsuch status when accounting for this component. The re-screening process implementedin this study emphasizes the importance of updating protocols to incorporate newdata and climate change projections for more accurate risk screening. Analysisshowed varied responses to climate change among species, with implications formanagement strategies. Salmonids exhibited nuanced responses, suggesting theneed for tailored management approaches. Confidence levels were generally medium,highlighting the importance of continual refinement. Our study underscores thenecessity of regularly updating non-native species risk screenings and follow-upassessments to account for newly available literature information. By integratingnew data and climate change scenarios, the effectiveness of management strategiescan be enhanced with the aim of safeguarding aquatic ecosystems and theirbiodiversity. Further research should focus on refining the entire risk analysisprocess and understanding species responses to changing environmental conditionsto inform proactive management approaches.
... Because the time-lag between species introduction and naturalisation can be decades to centuries, many studies have relied on historical records of introductions to identify species that have succeeded or failed to naturalise, with a focus on identifying traits that characterise successful invaders (McIntyre et al. 2005;Pysek et al. 2007;Diez et al. 2009;van Kleunen et al. 2010;McKnight et al. 2017;Peoples and Goforth 2017). Several challenges confront these studies. ...
... Because both residence time and planting effort are strong determinants of naturalisation probability, traits reflecting human preferences may be indirectly linked to naturalisation success through relationships with the timing of introductions and planting effort. Few studies have attempted to untangle these direct and indirect relationships, and to distinguish traits that directly influence naturalisation success from traits indirectly associated with success through human preferences for early introduction and widespread planting (but see Mack and Lonsdale 2001;Gravuer et al. 2008;Maurel et al. 2016;Peoples and Goforth 2017). ...
Worldwide, many invasive plant species are garden escapees. While weed risk assessment can identify new plant introductions with weedy potential, it does not address the large number of non-native plant species already present in many regions, the majority of which are horticultural species. Here we evaluate the drivers of plant naturalisation success using historical data on the horticultural woody species planted in Canberra, Australia. Canberra provides a unique opportunity to study plant naturalisation as it is a planned city with extensive horticultural plantings originating from government nurseries that kept extensive records documenting the planting efforts from the city’s inception. We identified factors linked to naturalisation success in 1439 horticultural, woody, non-native species planted in Canberra over 150 years by fitting univariate and multivariate regression models, and identified both direct and indirect effects using path analysis in a Bayesian framework. We found species were more likely to naturalise with greater planting effort, longer residence time, smaller seeds and dispersal mechanisms linked to wind and animal vectors. Cold-hardy and tall plants were also more likely to naturalise, although cold hardiness and height mostly affected naturalisation success indirectly via planting effort. These findings can aid in generating quantitative risk assessment models to predict woody garden species that would naturalise and pose the greatest risk of becoming invasive in the future.
... The effects of biogeographic origin on invasion success or impacts are usually indirect, that is, they occur by influencing species' evolutionary history, environmental adaptation and propagule pressure (Peoples & Goforth, 2017 (Heckman et al., 2016). Second, the high environmental similarity between East China and Eastern North America suggests that species from these regions will share similar niche dimensions. ...
Aim
Biological invasions threaten biodiversity globally. Large‐scale studies of non‐native plant species invasiveness typically focus on identifying ecological differences between naturalized and invasive species that account for their spread from sites of initial establishment (i.e., invasion success). However, invasive species differ widely in the magnitude of their impacts, suggesting the characteristics that favour invasion success might not necessarily predict the consequences of that invasion. Here we test whether those factors that increase the probability of plant species invasion also explain the severity of impacts.
Location
China.
Methods
We compiled a database of the invasiveness, biogeographic origins, life history traits, and introduction history for 538 non‐native plants in China and modelled differences in (a) naturalized and invasive species; (b) the spatial extent of invasion; and, (c) the severity of invasion impacts among successful invaders.
Results
Invasion success and the spatial extent of invasion shared similar influencing factors. However, these clearly differed from the predictors of severe invasion impacts. Unintentionally introduced non‐native plants with shorter life cycles and longer residence times were more likely to become invasive and to invade a larger area, while taller plants introduced from the Americas tended to have more severe impacts on the native ecosystems of China.
Main Conclusions
These results illustrate the different roles of introduction history, biogeographical origin and biological traits in determining the invasion success and spatial extent of invasion versus the severity of invasive species impacts. We suggest that factors associated with evolutionary adaptation and population expansion might determine invasion success and extent, while traits related to the relative competitive ability of invasive species determine the severity of impacts. Identifying specific characteristics of species that distinguish among successful invaders most likely to result in more severe impacts could help with planning more effective interventions.
... Propagule pressure could swamp the effects of other mechanisms such as biotic resistance, preadaptation, habitat alteration, or climate matching (Lockwood et al., 2005). However, the effect of fishing demand on fish differentiation and nonnative richness were significant, albeit weaker than other variables examined in this study, leading us to suggest that propagule pressure is more likely contextual with other mechanisms (Pyšek et al., 2015;Maurel et al., 2016;Peoples & Goforth, 2017b). ...
Establishment of nonnative fishes and extirpations of native fishes have homogenized freshwater fish faunas, yet our understanding of the drivers of this process remain limited. We addressed this knowledge gap by testing three hypotheses about introductions and homogenization of fish communities is the eastern United States: First, whether nonnative fish introductions have caused fish faunas to become homogenized or differentiated; second, whether patterns of faunal change are related to native species richness, propagule pressure, and anthropogenic disturbance; third, whether invasion patterns are attributable to either biotic resistance or preadaptation. We compared taxonomic similarity among watersheds in historical and contemporary time steps, and modeled contributions of different drivers to faunal change within watersheds. Average similarity among watersheds nearly doubled in contemporary times, pointing to substantial fish faunal homogenization. No watersheds lost species; patterns of homogenization are attributable entirely to nonnative species invasion. Community change and nonnative richness were positively associated with agriculture-urban land use, recreational fishing demand, and elevation. Native richness negatively affected community change and nonnative richness. Nonnative species originated from watersheds with higher richness than the ones they invaded, suggesting a role for biotic resistance. Understanding how mechanisms operate across spatial scales will help guide future conservation efforts.
... Specifically, we use the records for sailing ships that transported birds from Europe to New Zealand in the period 1850-1885, when birds were most intensively shipped, to test whether survival through the transport stage of these invasions related to characteristics of the voyage (event-level) or of the species (Peoples & Goforth, 2017) shipped. We restricted our analyses taxonomically, to the order of passerine birds: These species were selected for transport largely with the same aim, to control insect pests, and were intended for direct release. ...
Abstract Invasive alien species are a major threat to biodiversity and human activities, providing a strong incentive to understand the processes by which alien invasion occurs. While it is important to understand the determinants of success at each of several invasion stages—transport, introduction, establishment, and spread—few studies have explored the first of these stages. Here, we quantify and analyze variation in the success of individual animals in surviving the transport stage, based on shipping records of European passerines destined for New Zealand. We mined the original documents of Acclimatisation Societies, established in New Zealand for the purpose of introducing supposedly beneficial alien species, in combination with recently digitized newspaper archives, to produce a unique dataset of 122 ships that carried passerines from Europe to New Zealand between 1850 and 1885. For 37 of these shipments, data on the survival of individual species were available. Using generalized linear mixed models, we explored how survival was related to characteristics of the shipments and the species. We show that species differed greatly in their survival, but none of the tested traits accounted for these differences. Yet, survival increased over time, which mirrors the switch from early haphazard shipments to larger organized shipments. Our results imply that it was the quality of care received by the birds that most affected success at this stage of the invasion process.
... Previous studies have provided empirical evidence for both naturalization of taxonomically/phylogenetically dissimilar exotics and pre-adaptation of similar exotics (Davies et al., 2011;Lambdon & Hulme, 2006;Ma et al., 2016;Marx, Giblin, Dunwiddie, & Tank, 2016;Ricotta, Godefroid, & Rocchini, 2010;Schaefer, Hardy, Silva, Barraclough, & Savolainen, 2011;Thuiller et al., 2010). Reconciling these opposing invasion scenarios requires a novel framework for species invasiveness that disentangles confounding processes (Pearson, Ortega, Eren, & Hierro, 2018;Peoples & Goforth, 2017). ...
Aim
Understanding the causes and consequences of biological invasions remains a challenge for several disciplines, including biogeography. One major issue in overcoming this challenge is disentangling the confounding mechanisms of species invasiveness and community invasibility. Here, we tackle this issue by applying a novel approach based on the phylogenetic affinities between exotic species and natives in the recipient community to elucidate naturalization and pre‐adaptation processes.
Location
Japan.
Taxon
Seed plants.
Methods
Geographical co‐occurrence data for 1,094 exotics and 4,869 native species (including 1,676 endemics) were created at the 10‐km grid‐cell and vegetation‐plot levels. For individual exotic species, standardized effect size of phylogenetic species variability (PSV SES ) of the recipient native assemblage (i.e. phylogenetic fields) was calculated and its clustering/over‐dispersion was tested, representing exotic invasiveness in relation to invasibility of native recipients. To identify drivers of species invasiveness, the correlation of PSV SES with species attributes, involving phylogenetic distance between each exotic and native species, was explored.
Results
Phylogenetic fields (PSV SES ) showed significant over‐dispersion (~16% exotics) or clustering (~14% exotics). Interspecific variation of PSV SES among exotics was substantially explained by species ecological attributes. Geographical extent and climatic niche widths were negatively correlated with PSV SES . Preference for human influence was positively correlated with PSV SES at the 10‐km grid‐cell level, but negatively at the vegetation‐plot level. Exotics colonized from the Palearctic and Indo‐Malay regions, which belong to the same biogeographical region as East Asia, tended to have clustered phylogenetic fields.
Main conclusions
Environmental filtering and biotic sorting both played a key role in exotic plant colonization, supporting both of Darwin's contradictory hypotheses of naturalization versus pre‐adaptation. Clustered phylogenetic fields indicated that an exotic colonizes its recipient assemblage through abiotic filtering (i.e. pre‐adaptation); at the same time, phylogenetic over‐dispersion was indicative of naturalization for exotics that occupied a biotic niche space among native recipients (i.e. naturalization). Phylogenetic field patterns depended on species’ ecological attributes, including phylogenetic relatedness between exotics and recipient natives, especially reflecting invasibility at the local‐community level.
... Species traits could also predictably influence lineage survival probability, but perhaps more important are likely to be the relationships between traits and propagule pressure and (indirectly) colonization pressure (Maurel et al. 2016;Peoples and Goforth 2017). In general, widespread, abundant species are more likely to be introduced to new environments, while large-bodied animal species are more likely to be deliberately translocated (Blackburn and Duncan 2001;Jeschke and Strayer 2006;Tingley et al. 2010;Blackburn et al. 2017). ...
A key question in invasion biology is why some regions have more alien species than others. Here, we provide a general framework to answer this. We model alien species richness as a function of the number of species introduced (colonization pressure) and the probability that each species establishes, which is a function of propagule pressure (the number of introduction events and the number of individuals per event) and the probability that a founding individual leaves a surviving lineage (lineage survival probability). With this model we show that: (a) alien species richness is most sensitive to variation in colonization pressure; (b) heterogeneity in lineage survival probability lowers the probability of population establishment, implying alien richness should be lower in more spatially or temporally variable environments; (c) heterogeneity in lineage survival probability leads to higher alien richness when a given propagule pressure is divided into more introduction events, each involving fewer individuals; and (d) we cannot quantify how specific components, such as lineage survival probability, influence alien species richness without data on other components and knowledge of how these covary. Overall, the model provides novel insights into the factors influencing alien species richness, and shows why we expect anthropogenic effects to be critical to this.
... Conversely, in favourable environmental conditions, where more species can grow, invasion will probably be more strongly limited by competitive dynamics. Finally, functional traits can also modulate the role of propagule pressure (Maurel, Hanspach, Kühn, Pyšek, & van Kleunen, 2016;Peoples & Goforth, 2017). For example, taller alien species with small and light seeds typically have good dispersal ability and might be less reliant on local introduction sources (Rejmanek & Richardson, 1996;Thomson, Moles, Auld, & Kingsford, 2011). ...
Aim
It is widely recognized that the prediction of invasion success at large biogeographical scales requires jointly accounting for alien species traits and local community filters, such as abiotic conditions, biotic interactions and propagule pressure. Despite this recognition, interactions between traits and community filters are generally neglected. Here, we aim to address this limitation by developing a hierarchical framework that builds on trait‐based theory to model occurrences of alien species as a function of spatially explicit variables, filtering invasions and their interactions with species traits.
Location
Herbaceous communities throughout France.
Time period
c. 1960–2012 (mostly after 1990).
Major taxa studied
Herbaceous plants.
Methods
Based on a large dataset of >50,000 community plots, we built a multispecies hierarchical model of the distribution of the 10 most widespread alien plants in French grasslands. In this model, we explicitly account for how plant height, specific leaf area (SLA) and seed mass affect the occurrence of alien species along gradients of human pressure, environmental conditions and native community composition. Finally, we contrast the results to native species responses along the same gradients.
Results
We show that two out of three traits significantly modulate the responses of species along these broad gradients. Alien plants with exploitative traits (i.e., tall and with high SLA) were less dependent on human pressure, more efficient in resource‐rich environments and better at avoiding competition from native species. These trait–gradient interactions were often unique to alien plants (e.g., human pressure was important only for supporting alien species with low SLA), even though trait ranges of alien and native species were comparable. Ultimately, the modelling of trait–gradient interactions allows spatially explicit estimations of invasion risks by novel species with particular sets of traits.
Main conclusions
By taking the best from multispecies distribution modelling and trait‐based theory, our framework paves the way for a generalized mechanistic understanding of how traits influence the success of alien plants and their spatial distributions.
... Logically, a greater number of animals per event and a greater number of introduction events leads to a greater probability of invasion success (Jeschke 2014). Time since introduction can also influence invasion success, where more time increases the chance of invasiveness (Peoples and Goforth 2017). As an intentional introduction, propagule pressure for Blue Catfish in Virginia's tidal rivers was high, and hundreds of thousands of catfish were stocked over many years with many different introduction events . ...
Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of the Chesapeake Bay, where their feeding ecology and potential impact on native species was largely unknown. We collected stomach contents from 16,110 Blue Catfish at 698 sites in three large subestuaries of the Chesapeake Bay (James, York, Rappahannock rivers). Cumulative prey curves revealed that sample size was sufficient for diet description, though 1,000 – 1500 stomachs were needed per river. Blue Catfish are opportunistic
generalists that feed on a broad array of plant and animal material. Logistic regression models reveal that Blue Catfish undergo significant ontogenetic diet shifts to piscivory at larger sizes (P<0.01) though the lengths at which these shifts occur varies by river system (500 – 900 mm total length; TL). Over 60% of Blue Catfish stomachs contained other invasive species, primarily Hydrilla verticillata and Asian clams Corbicula fluminea. Canonical Correspondence Analysis (CCA) revealed that salinity and season explained the most variation in Blue Catfish diet, while Generalized Additive Models (GAMs) demonstrated that there is considerable spatiotemporal and length-based variation in predation of species of concern. Species of concern include American Shad, American Eel, and river herring, which are imperiled, and blue crab, which support valuable fisheries in Chesapeake Bay. Predation of American Shad, American Eel, and river herring was rare (max predicted occurrence in Blue Catfish diets = 8%), while blue crab was much more common in the diet (max predicted occurrence =28%). Predation of American Shad and river herring peaks in freshwater areas in April, while predation of blue crab peaks in brackish areas in October. Predation of all species of concern is highest for large catfish (500 – 1000 mm TL). Field and laboratory-based estimates of consumption rate revealed that Blue Catfish feed at similar rates as Channel Catfish Ictalurus punctatus, and daily ration is estimated to be 2-5% bodyweight per day during warm temperatures, while peak feeding (maximum daily ration) can approach 10% bodyweight per day. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations.
