Expansion Of Invasive Species Research Articles

Long distance dispersal of monk parakeets

Invasive species threaten biodiversity all around the world and for this reason, identifying the causes and mitigating their effects is a priority in conservation biology. One of the most important factors when dealing with invasive species is dispersal, because the distribution of dispersal distances among members of a population can greatly affect the rate of spread of these invasive populations. Long distance dispersal events have a disproportionately large influence on dispersal kernel estimations, but because of restricted spatial sampling scales they are difficult to detect. Here we use an extensive database of 3,114 monk parakeets ringed in Barcelona city since 2002 as part of an extensive control program across Catalonia where 3,460 birds have been captured since 2013. Our aim was to describe these long–distance movements of monk parakeets. We recorded dispersal distances of over 10 km for a total of eight individuals. Long–distance dispersions were in all directions and both males and females were involved. While some individuals moved in their first year, others delayed dispersal several years. Given that long–distance dispersal events can have a large influence on the rate of range expansion of invasive species this information can be of great utility when modeling the dispersal and spread of the species.

Fitness‐related traits are maximized in recently introduced, slow‐growing populations of a global invasive clam

AbstractMany species are shifting their ranges and being forced to rapidly respond to novel stressful environmental conditions. Colonizing individuals experience strong selective forces that favor the expression of life history traits notably affecting dispersal and reproductive rates in newly invaded habitats. Limited information is currently available on trait variation within the invasive range despite being critical for understanding ecological and evolutionary factors that drive the process of range expansion of invasive species. Here we evaluated life history shifts in the widely introduced Asian clam Corbicula cf. C. fluminea within its invaded range. Through an exhaustive literature search, we obtained data for 17 invasive populations of this clam from different ecosystems worldwide. We tested the relationship between population and individual parameters relevant to the process of range expansion. Our main results are that recently introduced populations of clams were characterized by (a) low density and low rate of population increase, (b) earlier reproduction in slow‐growing populations of clams, and (c) no effect of density on population increase. All populations of the Asian clam analyzed in this study, which are fixed for one genotype (the lineage called Form A/R), experienced different selective environments in the introduced range. These findings support the perspective that adaptive phenotypic plasticity favored the expression of traits that maximize fitness in recently established populations, which faced stronger r‐selective forces relative to long‐established ones. We discuss the role of plasticity in facilitating rapid adaptation and in increasing the likelihood of populations to overcome difficulties associated with low densities and low population increase in newly invaded areas.

Climate change and expanding invasive species drive widespread declines of native trout in the northern Rocky Mountains, USA.

Climate change and invasive species are major threats to native biodiversity, but few empirical studies have examined their combined effects at large spatial and temporal scales. Using 21,917 surveys collected over 30 years, we quantified the impacts of climate change on the past and future distributions of five interacting native and invasive trout species throughout the northern Rocky Mountains, USA. We found that the occupancy of native bull trout and cutthroat trout declined by 18 and 6%, respectively (1993–2018), and was predicted to decrease by an additional 39 and 16% by 2080. However, reasons for these occupancy reductions markedly differed among species: Climate-driven increases in water temperature and decreases in summer flow likely caused declines of bull trout, while climate-induced expansion of invasive species largely drove declines of cutthroat trout. Our results demonstrate that climate change can affect ecologically similar, co-occurring native species through distinct pathways, necessitating species-specific management actions.

Prunus lusitanica L.: An Endangered Plant Species Relict in the Central Region of Mainland Portugal

Prunus lusitanica L. is a paleotropical relic species with an Ibero-Maghrebian distribution, which is presently considered as an endangered species, recognized by the Natura 2000 Network (92/43/EEC) as a priority habitat for conservation in Europe. The mountains in the Portuguese mainland central region offer the best location for this species to occur. The main objective of this study is to measure the current conservation status of the communities of P. lusitanica, through the collection of field data, such as the number of existing individuals of each population and their location, which will then be comparatively analyzed based on the previous literature, published at least 15 years ago. Soil characterization analysis was carried out and the main threats to conservation were identified. As a result, a decline of approximately 40% was observed in the number of individuals and in the quality of their habitat. The main threats to their conservation were found to be the seasonal occurrence of rural fires and the expansion of invasive species, such as Acacia dealbata Link and Ailanthus altissima (Mill.) Swingle. Finally, we present the main management methodologies that should be considered for the valorization of this important vegetational relic in the central region of mainland Portugal.

Gatekeepers of transformation: private landowners evaluate invasives based on impacts to ecosystem services

AbstractBiological invasions are not new, yet the anthropogenic drivers of global change have produced unprecedented ecological novelty through the expansion of invasive species. Private landowners play an important role in determining the trajectory of ecological transformations driven by invasives. Using the northern Great Plains of the USA as a case study, we examined private landowners' role as gatekeepers for an invasive species. We employed a factorial vignette survey experiment to understand how the impacts of an unnamed invasive grass modeled on Kentucky bluegrass (Poa pratensis L.) were related to landowners' acceptance of the species. We also explored the relationship between landowners' acceptance of the invasive grass and their management intention to reduce/control the species. Each landowner evaluated multiple vignettes that randomly varied based on how a novel grass species expanding in rangelands would affect provisioning services (season of forage availability, forage quality, forage quantity), regulating services (floral resources for pollinators, water infiltration and availability), and supporting services (grassland bird diversity, grass diversity). Acceptability was strongly associated with landowners' management intentions, and the status of all seven services was related to acceptability. Reductions to any ecosystem service reduced the acceptability of the invasive grass species; however, only increases in forage quality, forage quantity, and water regulation were related to increased acceptability of the invasive. Scenario modeling shows that landowners displayed greater sensitivity to losses in a suite of ecosystem services than to equivalent gains. Scenarios specific to ecosystem service trade‐offs and Kentucky bluegrass invasion indicate that ecological losses may need to be severe before individual landowners change their management practices to reduce/control the species. Given the high thresholds for individual behavioral change, engaging private landowners in collaborative management efforts, whether to control an invasive grass or guide management toward co‐existence, may be helpful to conserve desired biodiversity and the flow of ecosystem services from northern Great Plains grasslands.

Invasion and Spreading of Drosophila nasuta (Diptera, Drosophilidae) in the Caatinga Biome, Brazil.

Biological invasions are one of the main causes of biodiversity loss, and it is essential to understand the pattern and rate of expansion of invasive species outside their native distribution. In this study, we documented the invasion of the Asian fruit fly, Drosophila nasuta Lamb, in the Caatinga, and measured its geographical distribution in this environment, which covers 11% of the Brazilian territory. We collected drosophilids in eight sites distributed in the north of the Caatinga (in the state of Ceará), in the south (in Bahia), in the east (in Pernambuco), and in the west (in Piauí), as well as in sites in the central area of the biome. Drosophila nasuta occurred in all areas and was one of the most frequently occurring species in half of the sampled sites. We observed greater abundance in areas with arboreal vegetation and a possible preference of this species for areas with higher annual rainfall in the Caatinga. Of all the biomes where D. nasuta is found in Brazil, the area occupied in the Caatinga is the largest documented to date. Our results show D. nasuta's success in invading the Caatinga and the vast area this species has colonized in this biome. The success of this invasion can be explained by the high fertility and short life cycle as well as by the ability of D. nasuta to use different trophic resources.

Interactive effect of climate warming and nitrogen deposition may shift the dynamics of native and invasive species

AbstractAimsProjections of invasive species expansion under a warmer world often do not explicitly consider the concurring nitrogen (N) deposition. It remains largely unknown how the convoluted effect of climate warming and N deposition will shift the native and invasive species dynamics. Here, we hypothesize that the concurring increases in N and temperature would promote growth of invasive species greater than that of native species.MethodsA controlled greenhouse experiment was conducted to quantify the growth response of an invasive species (Solidago canadensis L.) and a co-existing native species (Artemisia argyi Levl. et Van) under the effects of climate warming, N deposition and their interactions.Important FindingsDue to the strong positive effect of N addition, the interactive effect of temperature increase and N addition resulted in an overall significant increase in growth of both invasive and native species, demonstrating that these manipulations may make microhabitats more favorable to plant growth. However, the relative increases in biomass, height and diameter of invasive S. canadensis were significantly lower than those of native A. argyi. This suggests that the vegetative growth superiority of invasive S. canadensis over the native species A. argyi is reduced by the enhanced N availability in the warmer world. Therefore, the inclusion of N deposition may mitigate the projection of invasive species S. canadensis expansion under climate warming.

Predicting the Current and Future Distribution of the Invasive Weed Ageratina adenophora in the Chitwan–Annapurna Landscape, Nepal

With increasing globalization, trade, and human movement, the rate of alien species introduction has increased all around the globe. In addition, climate change is thought to exacerbate the situation by allowing range expansion of invasive species into new areas. Predicting the distribution of invasive species under conditions of climate change is important for identifying susceptible areas of invasion and developing strategies for limiting their expansion. We used Maxent modeling to predict the distribution of one of the world's most aggressive invasive weeds, Ageratina adenophora (Sprengel) R. King and H. Robinson, in the Chitwan–Annapurna Landscape (CHAL) of Nepal under current conditions and 3 future climate change trajectories based on 3 representative concentration pathways (RCPs 2.6, 4.5, and 8.5) in 2 different time periods (2050 and 2070) using species occurrence data, and bioclimatic and topographic variables. Minimum temperature in the coldest month was the most important variable affecting the distribution of A. adenophora. About 38% (12,215 km2) of the CHAL area is climatically suitable for A. adenophora, with the Middle Mountain physiographic region being the most suitable one. A predicted increase in current suitable areas ranges from 1 to 2% under future climate scenarios (RCP 2.6 and RCP 8.5). All protected areas and 3 physiographic regions (Siwaliks, High Mountain, High Himalaya) are likely to gain climatically suitable areas in future climate scenarios. The upper elevational distribution limit of the weed is expected to expand by 31–48 m in future climate scenarios, suggesting that the weed will colonize additional areas at higher elevations in the future. In conclusion, our results showed that a vast area of CHAL is climatically suitable for A. adenophora. Expected further range expansion and upslope migration in the future make it essential to initiate effective management measures to prevent further negative impacts of this invasive plant.

Tidal channel-mediated gradients facilitate Spartina alterniflora invasion in coastal ecosystems: implications for invasive species management

Understanding how geomorphic landscape features affect physical habitat conditions is essential for predicting if such geomorphic landscape features may act as conduits facilitating invasive species expansion in coastal ecosystems. Although the effects of various abiotic and biotic factors on plant invasion in salt marshes have been well studied, little is known about the impact of tidal channels on plant invasion. Here, we examined the effects of bottom-up determinants on the lateral expansion of Spartina alterniflora in tidal channel margins of different elevational marsh zones: the low, middle and high marsh, in the Yellow River Delta, China. Field observations and experiments showed that the microhabitats of tidal channel margins are characterized by relatively low soil salinity and high inundation, which significantly facilitated the establishment, growth, colonization and sexual reproduction of S. alterniflora. Moreover, the facilitating effect of tidal channel margins on plant landward invasion appeared more sensitive in middle and high marshes compared with the low marshes. High propagule pressure combined with suitable physical conditions of the structural microhabitats formed within tidal channels potentially promoted the rapid expansion of S. alterniflora along the tidal channel margins. Based on these results, a conceptual model was built illustrating the lateral expansion mechanisms of the invasive plant mediated by tidal channels. These results highlight the importance of tidal channel-mediated gradients in bottom-up abiotic and biotic-dispersal factors in facilitating the expansion of coastal invasive plants. For wetlands management, our results imply that geomorphic landscape features should be incorporated into ecological management and risk assessment of invasive plants.

Predicting range expansion of invasive species: Pitfalls and best practices for obtaining biologically realistic projections

AbstractAimSpecies distribution models (SDMs) are widely used to forecast potential range expansion of invasive species. However, invasive species occurrence datasets often have spatial biases that may violate key SDM assumptions. In this study, we examined alternative methods of spatial bias correction and multiple methods for model evaluation for seven invasive plant species.LocationNorth America.TaxonCommon Tansy (Tanacetum vulgare), Wild Parsnip (Pastinaca sativa), Leafy Spurge (Euphorbia virgata), Common Teasel (Dipsacus fullonum), Brown Knapweed (Centaurea jacea), Black Swallowwort (Vincetoxicum nigrum) and Dalmatian Toadflax (Linaria dalmatica).MethodsWe employed bias‐correction measures for both occurrence sampling and background sampling inputs in a factorial design for Maxent resulting in six potential models for each species. We evaluated our models for complexity, model fit and using commonly employed evaluation metrics: AUC, partial AUC, the continuous Boyce index and sensitivity. We then developed a structured process for model selection.ResultsModels developed without occurrence or background bias correction often were overly complex and did not transfer well to expanding range fronts. Conversely, models that employed occurrence and/or background bias‐correction measures were less complex, had better AICc scores and had greater projection into incipient areas. These simpler models were also more likely to be selected when evaluated using a process that integrated multiple evaluation metrics. We found that invasion history (e.g. established versus incipient) was associated with the effectiveness of spatial bias correction techniques.Main ConclusionsWhile challenges exist in building climate‐based correlative species distribution models for invasive species, we found that methods relying on maximizing AUC performed poorly for invasive species. We advocate for the use of multiple and diverse metrics for model evaluation. Users of species distribution models need to incorporate explicit consideration of model discrimination, model fit and model complexity into their decision‐making processes if they are to build biologically realistic models.

A regional approach to climate and health adaptation in the Middle East

Abstract Background The Middle East (ME) is expected to be influenced by climate changes that will significantly affect human health. An increase in temperature and in the intensity, length and frequency of heat waves, alongside a decrease in precipitation, have been observed, and longer summers and shorter winters are expected. Population growth intensifies the stress on water and the ecosystem in an already sensitive region. Moreover, political conflicts intensify the vulnerability of the region's population and prevent cross-border collaboration and knowledge transfer. The aims of this talk are to: 1) present climate scenarios and potential health risks for the ME; and 2) present a regional inter-disciplinary collaboration that focuses on climate and health research. Methods To prioritize regional research directions, a group of climatologists and public health researchers from the ME and Europe convened in an expert workshop, which included a process of consensus-building regarding research priorities and potential collaboration. Results Associated health risks are mainly increases in morbidity and mortality due to heatwaves, and increases in potentially deadly vector- water- air- and food-borne diseases such as chikungunya, yellow fever and dengue fever, due to expansion of invasive species of mosquitoes. There are wide economic and infrastructure gaps among the region's countries, entailing different levels of preparedness. Countries also face multiple intra- and inter-country political conflicts and instability which further weaken their ability to adapt at the regional level. However, climate change has regional impacts which should be understood and mitigated at that level. Research priorities include spatio-temporal research on heat and health outcomes; regional surveillance of infectious diseases; and preparedness of health systems and pathways for collaboration among health agencies in the midst of a political conflict with an emphasis on vulnerable populations. Key messages Inter-sectoral and inter-disciplinary work is a known requirement for tackling climate change challenges. Structural changes are needed at both the local and regional levels to fulfill this vision. Political conflicts in the Middle East weaken the ability to adapt to climate change in a vulnerable region.

Invaders induce coordinated isotopic niche shifts in native fish species

Food-web investigations inform management strategies by exposing potential interactions between native and nonnative species and anticipating likely outcomes associated with species removal efforts. We leveraged a natural gradient of compositional turnover from native-only to nonnative-only fish assemblages, combined with an intensive removal effort, to investigate underlying food-web changes in response to invasive species expansion in a Lower Colorado River tributary. Nonnative fishes caused coordinated isotopic niche displacement in native fishes by inducing resource shifts toward lower trophic positions and enriched carbon sources. By contrast, nonnative fishes did not experience reciprocal shifts when native fishes were present. Asymmetrical outcomes between native and nonnative fishes indicated species displacement may result from competitive or consumptive interactions. Native species’ isotopic niches returned to higher trophic levels after nonnative green sunfish (Lepomis cyanellus) removal, indicating removal efforts can support trophic recovery of native fishes like desert suckers (Catostomus clarkii) and roundtail chub (Gila robusta). Using stable isotope analysis in preremoval assessments provides opportunities to identify asymmetric interactions, whereas postremoval assessments could identify unintended consequences, like mesopredator release, as part of adaptive decision making to recover native fishes.

Exploring larval phenology as predictor for range expansion in an invasive species

Predicting range expansion of invasive species is one of the key challenges in ecology. We modelled the phenological window for successful larval release and development (WLR) in order to predict poleward expansion of the invasive crab Hemigrapsus sanguineus along the Atlantic coast of North America and north Europe. WLR quantifies the number of opportunities (in days) when larval release leads to a successful completion of the larval phase; WLR depends on the effects of temperature on the duration of larval development and survival. Successful larval development is a necessary requirement for the establishment of self‐persistent local populations. WLR was computed from a mechanistic model, based on in situ temperature time series and a laboratory–calibrated curve predicting duration of larval development from temperature. As a validation step, we checked that model predictions of the time of larval settlement matched observations from the field for our local population (Helgoland, North Sea). We then applied our model to the North American shores because larvae from our European population showed, in the laboratory, similar responses to temperature to those of a North American population. WLR correctly predicted the northern distribution limit in North American shores, where the poleward expansion of H. sanguineus appear to have stalled (as of 2015). For north Europe, where H. sanguineus is a recent invader, WLR predicted ample room for poleward expansion towards NE England and S Norway. We also explored the importance of year‐to‐year variation in temperature for WLR and potential expansion: variations in WLR highlighted the role of heat waves as likely promoters of recruitment subsidising sink populations located at the distribution limits. Overall, phenological windows may be used as a part of a warning system enabling more targeted programs for monitoring.

Shipwrecks help invasive coral to expand range in the Atlantic Ocean

The invasive coral Tubastraea tagusensis (sun coral) is a habitat-forming species currently increasing its geographical range into the Atlantic Ocean, thereby causing negative ecological and socioeconomic impacts. Scuba divers observed this coral in the western equatorial Atlantic in January 2020, growing at high densities on a shipwreck from World War II (sunk in 1943) at a depth of approximately 32 m. Available footage from the beginning of the decade (2012–2018) shows no obvious signs of sun coral on this shipwreck, suggesting recent colonization and range expansion. The recent evidence of expansion was found 200 km east of the last record, which was also found on a WWII shipwreck (sunk in 1942) in 2016. We have identified hundreds of overlooked WWII shipwrecks, as well as new wrecks in shallow and mesophotic waters, that may provide stepping-stone habitats for this coral to expand its distribution in the Atlantic. We discuss the role of shipwrecks as a network of stepping stones for the sun coral spread, creating complementary paths for the invasiveness by overcoming physiological traits and the short lifespan of the coral larvae. Previous research underestimates the importance of these artificial stepping-stone patches in sustaining crucial dispersal events and range expansion of invasive species. These results are a call to action to manage the invasive Tubastraea corals at a national and international scale in the Atlantic basin.

Seagrass coastal protection services reduced by invasive species expansion and megaherbivore grazing

Abstract Seagrasses provide an important ecosystem service by creating a stable erosion‐resistant seabed that contributes to effective coastal protection. Variable morphologies and life‐history strategies, however, are likely to impact the sediment stabilization capacity of different seagrass species. We question how opportunistic invasive species and increasing grazing by megaherbivores may alter sediment stabilization services provided by established seagrass meadows, using the Caribbean as a case study. Utilizing two portable field‐flumes that simulate unidirectional and oscillatory flow regimes, we compared the sediment stabilization capacity of natural seagrass meadows in situ under current‐ and wave‐dominated regimes. Monospecific patches of a native (Thalassia testudinum) and an invasive (Halophila stipulacea) seagrass species were compared, along with the effect of three levels of megaherbivore grazing on T. testudinum: ungrazed, lightly grazed and intensively grazed. For both hydrodynamic regimes, the long‐leaved, dense meadows of the climax species, T. testudinum provided the highest stabilization. However, the loss of above‐ground biomass by intensive grazing reduced the capacity of the native seagrass to stabilize the surface sediment. Caribbean seagrass meadows are presently threatened by the rapid spread of the invasive opportunistic seagrass, H. stipulacea. The dense meadows of H. stipulacea were found to accumulate fine sediment, and thereby, appear to be effective in reducing bottom shear stress during calm periods. This fine sediment within the invasive meadows, however, is easily resuspended by hydrodynamic forces, and the low below‐ground biomass of H. stipulacea make it susceptible to uprooting during storm events, potentially leaving large regions vulnerable to erosion. Overall, this present study highlights that intensive megaherbivore grazing and opportunistic invasive species threaten the coastal protection services provided by mildly grazed native species. Synthesis. Seagrass meadows of dense, long‐leaved species stabilize the sediment surface and maintain the seabed integrity, thereby contributing to coastal protection. These services are threatened by intensive megaherbivore grazing, which reduces the stability of the surface sediment, and opportunistic invasive species, which are susceptible to uprooting in storms and thereby can leave the seabed vulnerable to erosion.

Responses of lake macrophyte species and functional traits to climate and land use changes

Aquatic plants are essential components in the regulation of microhabitat complexity and physico-chemical parameters in lake ecosystems. Increased eutrophication, land use change, modification of hydrological regimes, and expansion of invasive species are expected to impact aquatic plant community composition; however, historical pathways and response patterns are not well understood at the national scale. We analyzed temporal changes in aquatic plant communities in Japan from the early 1900s to the 2000s using field survey records from 248 lakes. Relationships of species associations with climate, land use, and lake characteristics were described using a joint species distribution model. The mean variation attributable to lake characteristics was 25.4%, followed by climate (14.0%), and land use (10.5%). Among the 13 functional traits used in our analysis, sexual and pollination traits showed marked responses to precipitation and land use. Hypohydrophily increased with precipitation, whereas monoecious aquatic plants increased in lakes surrounded by urbanized area. The relative ratio of floating to submerged plants has increased over time. Our results provide insight into long-term changes in aquatic plant communities and identify functional traits sensitive to environmental change.

Patterns of Vespa velutina invasion in Portugal using crowdsourced data

Abstract The invasive yellow‐legged hornet (Vespa velutina) was first detected in mainland Portugal in September 2011. The lack of information regarding the processes of species spread has hampered the development of adequate measures to mitigate the potential impact of this invasive predator. Crowdsourced data, i.e., information opportunistically reported by citizens, can facilitate the collection of numerous species occurrence records over large spatial scales, which can be valuable to understand the expansion of invasive species. Here, using validated crowdsourced data on the precise location of 49 013 nests, we: (i) update information regarding V. velutina distribution in Portugal; (ii) estimate the species expansion rate; and (iii) analyse the patterns of nests distribution at national and local scales. The species is currently distributed over an area of approximately 57 000 km2, which corresponds to 62% of mainland Portugal. We estimated an average rate of 37.4 ± 13.2 km/year for V. velutina expansion. Vespa velutina nests presented an aggregated distribution and nest density at the urban local‐scale was estimated in 5.4 ± 3.3 nests/km2. The observed decrease in the nearest‐neighbour nest distance over the years suggests that the density of nests has not reached its limit. We advocate that the development of a cheap and rapid method for nest detection and the study of fine‐scale mechanisms leading to V. velutina dispersal are important steps to identify colonisation pathways and plan management approaches aiming to halt species spread and impact in apiaries.

Climate-induced expansions of invasive species in the Pacific Northwest, North America: a synthesis of observations and projections

Climate change may facilitate the expansion of non-native invasive species (NIS) in aquatic and terrestrial systems. However, empirical evidence remains scarce and poorly synthesized at scales necessary for effective management. We conducted a literature synthesis to assess the state of research on the observed and predicted effects of climate change on a suite of 398 aquatic and terrestrial NIS now present in or a major threat to aquatic and terrestrial ecosystems of the Pacific Northwest (PNW), USA and British Columbia. Surprisingly, very few studies (n???=???15) have investigated the observed effects of climate change on the distribution, abundance, spread, or impact of the focal NIS, with only five studies focusing on terrestrial (n???=???2) or aquatic (n???=???3) species within the PNW. Only 93 studies predicted the future dynamics of the focal NIS somewhere in their non-native range using climate model projections, yielding 117 species-specific predictions. However, only 30 of those studies generated predictions that overlapped with the PNW, and only six focused specifically on the expansion or abundance of NIS (n???=???11 species) entirely within the region. Although our understanding of how climate change may interact with biological invasions is notably lacking, some evidence suggests that climate-induced NIS expansions are already underway in the PNW, particularly in aquatic ecosystems, and will be exacerbated by future changes in temperature and precipitation regimes. Better information is urgently needed for managers to implement strategic prevention, early detection, and proactive actions that ameliorate ecologically and economically devastating impacts of NIS.

Integrating climate, water chemistry and propagule pressure indicators into aquatic species distribution models

Species distribution models are frequently used to anticipate the expansion of invasive species under the assumption that climate affects habitat conditions. Here, we investigated the influence of two additional factors that determine the spread, establishment, and impact of aquatic organisms: propagule pressure and water chemistry. Our case study species is the New Zealand Mud Snail (Potamopyrgus antipodarum, Tateidae, Mollusca), one of the 100 worst invasive species in Europe. We calibrated species distribution models combining three types of indicators (climate, water chemistry, and propagule pressure), and two scales (Iberian Peninsula vs. Ebro River catchment) using the Maxent algorithm. Propagule pressure improved the accuracy of models and enlarged the area susceptible to invasion by 16% at the Iberian Peninsula scale, and by 36% at the catchment scale. Among propagule pressure indicators, accessibility was the single most important indicator of the species distribution (33–35% contribution), illustrating the role of human-mediated dispersal for aquatic invaders. The catchment model integrating climate, propagule pressure and water chemistry indicators was the best option to prioritize river segments most vulnerable to colonization, characterized by high temperature, human influence and water pollution (nitrate concentration). High risk areas according to our models include the Mediterranean and North Atlantic coasts, central Spain, and the lowlands of the Ebro River catchment. Based on this study, we recommend including indicators of propagule pressure such as accessibility to reflect the opportunity to invade, and using water chemistry to further prioritize the river stretches most suitable to invasion. We conclude that distribution models integrating indicators at multiple scales are feasible, consistent in their predictions across scales, and show great potential to optimize management resources towards the prevention and early eradication of aquatic invasive species.

LOCAL COMMUNITIES AND MURE. FLOODPLAIN NATURAL PARK ROMANIA: A COMMON FIGHT AGAINST INVASIVE SPECIES

Invasive plant species, like Indigo bush (Amorpha fruticosa L.), Boxelder (Acer negundo L.), Japanese knotweed [Fallopia japonica (Houtt.) Ronse Decr] are altering the conservation status of terrestrial ecosystems along the Mure. Floodplain Natural Park in Romania. On a long run, and a large geographic scale, the invasive species have a high potential to generate a negative impact on the environment and the economy. Hence there is a stringent need of preventing, tracking down, and controlling invasive species. The research was carried out along with an awareness campaign meant to raise the knowledge of the local population regarding the danger of continuous expansion of invasive species through unsustainable agricultural practices. The fieldwork was conducted between September 2015 and April 2017 and consisted of a survey filled in by 240 respondents. After applying the principal component analysis on the answers given to a set of closed questions, we found that most of the attendees considered the meetings and the dissemination materials as important, but some local communities are against fighting Indigo-bush and other invasive species, and consider the cost of intervention is too high. This discrepancy between the degree to which local people appreciated the project and the degree to which they really want to get involved in fighting invasive species shows that grassroots awareness campaigns are still needed.