Expansion Of Invasive Species Research Articles

Integrating univariate niche dynamics in species distribution models: A step forward for marine research on biological invasions

AbstractAimThe development of approaches to predict the distribution and potential expansion of invasive species is still an open challenge. Here our goal is to improve the modelling procedure for marine invaders by coupling Species Distribution Models (SDMs) with an analysis of their univariate niche dynamics. In particular, we tested for the first time whether choosing model predictors among the stable niche dimensions was effective in improving predictions of invasive species expansion.LocationMediterranean Sea.TaxonDusky spinefoot, Siganus luridus.MethodsWe analysed the univariate niche dynamics for S. luridus across its native and invaded ranges, by applying a standardized framework that allowed the identification of cases of niche stability or shift. We compared inter‐range transferability of SDMs fitted with different combinations of labile or stable predictors. Finally, we evaluated interactions in SDM settings (calibration area, model technique and predictors set) on models’ predictive ability, using independent data from the most recent phase of invasion.ResultsWe detected a pattern of niche stability for several variables, especially salinity and bathymetry, which positively influenced model inter‐ranges transferability: when the models calibrated in the native range include only stable niche axes, predictive ability is improved. We also identified a shift towards lower surface temperatures in the introduced range, which were almost never experienced by the species before invasion. The model calibrated within the combined ranges was the most ecologically congruent. Also, models calibrated in the invaded range allowed a correct prediction of range expansion, with the predicted suitable areas only slightly underestimated.Main conclusionsWe provide the first evidence that using conserved predictors in SDMs improves inter‐range projections of expanding invasive species. Variable selection, calibration area and modelling technique all matter when modelling invasive species, with important interaction effects. We provide guidelines on how to improve SDMs applications in biological invasion research.

Indicator based integrated vulnerability assessment of community forests in Indian west Himalaya

The Himalaya is often referred to as forested landscape, which provides a range of ecosystem services vital for sustaining life of billions of people. The region is recognized amongst the 35 global biodiversity hotspots for its unique and rich biodiversity. Also, the region is highly vulnerable to perturbations due to anthropogenic disturbances and climate change. Especially the forests in the region are subject to stress from such perturbations. The higher dependency of communities on forests and changing climate has impacts on structure and function of forest ecosystems. This has severe implications for forest dependent communities. Therefore, vulnerability assessment of forests is urgently needed to understand the likely consequences of these changes and responses. Such information would help in developing better management and conservation planning. Earlier studies on vulnerability assessment of forests and forest-dependent people have failed to acknowledge the importance of spatial and temporal aspects of vulnerability investigated through field based observations. Realizing this, present study focuses on forest vulnerability assessment through field based observations along an altitudinal gradient (700–3400 m) in the Indian west Himalaya. This study, for the first time, provides vulnerability assessment of community forests at local scale following integrated approach of multiple indicators across diverse domains. The vulnerability indicators have been identified through a systematic analysis and extensive review of the available literature. A total of 14 indicators in six domains (viz. forest, climate, anthropogenic, topographic, soil and management practices) were identified to assess inherent vulnerability of Community Forests (Van Panchayats) in the target region. Furthermore, Forest Vulnerability Index (FVI) was calculated by integrating the selected indicators across domains. The results revealed high vulnerability at low altitude (<1200 m) forests. Disturbance index, expansion of invasive species and people dependency has emerged as the major factors responsible for forest vulnerability in the region. The value of FVI declined significantly (R2 = 0.51, p < 0.001) with increasing altitude range. The study also analysed perceptions of inhabitant community regarding dependency on forest resources, management practices and status of community forest in the studied area. The outcomes of this study would help in developing management interventions and strategies to ensure sustainable management of forest resources in the targeted landscape in particular and Indian Himalaya in general.

The impact on plant communities of an invasive alien herb, Oenothera drummondii, varies along the beach-coastal dune gradient

One of the major threats to the diversity of coastal dunes is the expansion of invasive species, such as Oenothera drummondii subsp. drummondii (Onagraceae). In southwestern Spain, we studied the impact of this American invasive on community structure and composition along a beach-dune gradient (beach, foredune, and inland dunes). Differences in density, biomass, and the cover of O. drummondii, the cover of perennial and annuals/biennials species, and Shannon diversity index H’ and dominance λ were compared between invaded and uninvaded sectors. We observed that the intensity and impact of the invasion by O. drummondii varies along the beach-dune gradient. The abundance of the invasive plant increased inland and in consequence, its impact on species richness and composition was highest in inland dunes. Here, plant cover of O. drummondii represented 57.9% of total plant cover; species richness was reduced (with 3.3 fewer species per 2 × 2m plot), diversity H’ was lower while dominance λ was higher. At a broader scale, species richness in the invaded sector was 25% larger than in the uninvaded sector, because of the presence of ruderal species. Species composition also was modified after the invasion. The abundance of a keystone native species was largely reduced (Ammophila arenaria), and some natives became locally extinct (Otanthus maritimus, Eryngium maritimum, Medicago marina and Elymus farctus). We conclude that the high environmental severity of the beach and foredunes results in a reduced invasion and impact of O. drummondii, whereas the milder conditions of inland dunes promote its expansion. The shift in community structure and composition can have an increasing domino effect and thus monitoring, and mitigation actions are necessary. When doing so, the environmental heterogeneity of the beach-dune gradient should be considered, given its relevance in the invasion process.

Spread of the non-native anemone Anemonia alicemartinae Häussermann & Försterra, 2001 along the Humboldt-current large marine ecosystem: an ecological niche model approach.

The geographical expansion of invasive species depends mainly on its dispersal potential, and the abiotic and biotic factors affecting it. Knowing the invasive dynamic of non-native species, as well as its behavior at different natural or anthropogenic scenarios, is fundamental for planning conservation management policies and control plans. The invasive sea anemone Anemonia alicemartinae in habits from the north (18°S) to the south-central (36°S) coast of Chile and its distribution range has expanded by approximately 1,928 km in the last 50 years. Previous works have proposed that human-mediated southward transport associated with regional-scale maritime activities could explain its rapid spread. To evaluate this hypothesis, we used ecological niche models (ENM) to evaluate the potential colonization of the southernmost area of South America. Additionally, we conducted a post hoc analysis to evaluate the relationship between the prediction of the ENM and human activity measured as the number of landings of ships in ports. The models were built based on presence records of A. alicemartinae, and oceanographic variables. Results showed that sea surface salinity and annual sea surface temperature (variance) are the best predictor variables to explain the distribution of A. alicemartinae. There was a positive and significant relationship between the geographical distribution of the sea anemone predicted by the ENM and the number of landings, as a proxy of anthropogenic activity. The most susceptible areas to invasion were those that showed the highest variability in both oceanographic predictors. These areas included the Biobío region, Chiloé´s inland sea, Aysén, and Chacabuco regions, which together comprise two biogeographical provinces. These results sustain the proposed hypothesis and, overall, the results suggest that along with the characteristics of the life history of A. alicemartinae, oceanographic conditions and maritime transport as vector contribute to the southern range expansion of this invasive cryptogenic species in the Humboldt-current large marine ecosystem.

Theory and practice to conserve freshwater biodiversity in the Anthropocene

Abstract The unprecedented impact of human activities on nature has led scientists to propose we might now be in a new geological epoch: the Anthropocene. Significant human alterations of freshwater systems include massive changes to soil erosion–deposition dynamics, hydrological regimes via impoundment and diversion, land‐use conversion, chemical and nutrient pollution, and human‐assisted range expansion of invasive species. In this human‐dominated epoch, biodiversity, which includes all life on Earth, is at risk, and freshwater biodiversity shows the strongest examples of the extent of this threat. We live in a world where it is necessary to find optimal ways to balance the growing human need for fresh water with ensuring that freshwater ecosystems remain functional in support of the biodiversity that inhabits them and the services these systems provide. Within the broader context of freshwater management in the Anthropocene, this special issue targets freshwater biodiversity and habitat conservation through a variety of lenses. Four main areas of emphasis include: conservation approaches; advances in model and tool development; enhancing water planning; and management and protection of species and habitats. For manuscripts included in this special issue, all authors were instructed to demonstrate how the material presented, be it commentary, conservation prioritization, new methodology or other subject matter, is broadly applicable and transferable.

La influencia humana, clave para entender la biogeografía de especies invasoras en el Antropoceno

Las invasiones biológicas han revolucionado el concepto de biogeografía en el Antropoceno, ya que su distribución geográfica ya no depende de su capacidad intrínseca de movimiento y las barreras biogeográficas clásicas, sino que depende directamente de actividades humanas que favorecen, intencionada o accidentalmente, su expansión. Por tanto, las técnicas de modelización geográfica han de tener en cuenta las particularidades de las especies invasoras para poder anticipar su distribución potencial en el futuro. En este estudio, utilizamos un listado de 57 de las peores especies invasoras en Europa (18 plantas, 15 vertebrados, 12 invertebrados y 12 organismos acuáticos) para comparar la influencia climática y humana en la distribución a gran escala de especies invasoras. Identificamos un total de nueve grandes vectores de introducción, entre los que destacan el transporte, el cultivo ornamental y el comercio. Localizamos siete variables relacionadas con estos vectores de introducción que utilizamos junto con variables climáticas como predictores en Modelos Ecológicos de Nicho (MEN): accesibilidad, densidad de población, PIB, grado de antropización, cobertura de uso agrícola y urbano, distancia a carreteras y puertos comerciales. La temperatura mínima anual es el predictor más importante en los modelos, seguida de la distancia a puertos, el PIB y la accesibilidad. Sorprendentemente, los modelos que incluyen variables humanas no son estadísticamente mejores que los basados en variables climáticas únicamente, si bien predicen un aumento medio del 8% en la superficie europea susceptible a la invasión. Tal incremento se produce fundamentalmente en zonas muy antropizadas donde la posibilidad de invasión es obviamente mayor. En el caso de la Península Ibérica, esto se traduce en un aumento del riesgo de invasión en la zona de levante, valle del Ebro y alrededores de grandes ciudades. Concluimos por tanto que el clima es importante, pero no suficiente para anticipar efectivamente la expansión de especies invasoras, y por tanto, cualquier información disponible que esté directamente relacionada con los vectores de introducción ha de ser incorporada de forma rutinaria en los MEN para optimizar los recursos dedicados a la prevención, respuesta rápida y control a largo plazo de especies invasoras.

Niche expansion of the invasive plant species Ageratina adenophora despite evolutionary constraints

AbstractAimEcological inferences drawn from studies on niche dynamics of invasive species are often limited due to difficulties in disentangling evolutionary adaptations of the fundamental niche from demographic and interspecific processes shaping the realized niche. We used Ageratina adenophora, an invasive plant with restricted evolutionary potential to investigate shifts in the realized climatic niche independent of potential evolutionary adaptations.LocationNative Mexican range; exotic ranges in Asia, the USA, the Canary Islands and Australia.TaxonInvasive Asteraceae A. adenophora (Spreng.) R.M.King &amp; H.Rob. Commonly known as Crofton weed.MethodsWe compiled a robust occurrence dataset of A. adenophora for its native Mexican range and four exotic ranges (Asia, USA, Canary Islands, and Australia) and quantified pairwise niche overlap (Schoener's D) and niche dynamic (stable, unfilling and expansion) indices between the native and exotic ranges in reduced climatic space using smoothed occurrence densities. Niche shift was statistically tested using niche equivalency tests.ResultsThe value of niche overlap (Schoener's D) differed considerably, ranging from relatively high between Mexico and Asia to low between Mexico and Australia. The niche dynamic indices indicated highest level of niche stability in Asia while highest degree of unstable niche was detected in Australia due to both niche expansion and unfilling. The niche similarity tests indicated that the native niche is more similar to the exotic niche than any randomly sampled niche from the exotic range. However, the niche equivalency tests showed evidence of niche differentiation as the observed niche overlap was lower than expected by chance for all pairwise comparisons. Jointly these tests indicate that despite the similarity, the native niche is not perfectly identical to any of the exotic niches.Main conclusionsThe current study has direct implications for understanding range expansion of invasive species even in the absence of evolutionary adaptation. Our study indicates that invasive species can occupy different, non‐consistent realized climatic niches in different parts of the world, thus limiting the transferability of species distribution models and corresponding risk assessments or future projections.

Spatio-temporal dynamics of the invasive orchid Oeceoclades maculata (Orchidaceae), in four different habitats in southeast Chiapas, Mexico

The expansion of invasive species is a global concern. Within the Orchidaceae there are a number of invasive species. One of the most widely distributed invasive orchids in Mexico is Oeceoclades maculata (Lindl.) Lindl. By examining the population dynamic variations of an invasive species in its range of expansion, we can identify the factors that have contributed to that variation. Life Table Response Experiments (LTRE) were used to describe the dynamic of four populations of O. maculata in different ecosystems in south Chiapas, Mexico. Our goals were to quantify the contributions of differences between years and sites, and their interactions, to overall differences in population growth rate (λ), and to underlying vital rates. Fertility, survival and growth made the largest contributions, both positive and negative, to annual differences in λ. Spatial variations in λ were also found. The largest plants (S3 and S4) made the contributions of greatest magnitude each year and in each site. In seven of eight cases, the inclusion of the interaction term gave a better estimate of the population growth rate. This investigation highlights the need for taking into account life-history variations at different scales when the research goal is to study expansion of an invasive species in a heterogeneous landscape. The usefulness of LTRE studies was also demonstrated to better understand the natural history of the species and thus lay the groundwork for planning efficient management strategies, either for the conservation of rare, endangered species, or for the control of invasive species.

Artificial wave breakers promote the establishment of alien aquatic plants in a shallow lake

We surveyed the occurrence of three emergent alien aquatic plants, Gymnocoronis spilanthoides, Alternanthera sessilis, and Alternanthera philoxeroides, in Lake Kasumigaura from 2013 to 2017. To determine the effects of shoreline modification on the expansion of alien aquatic plants, we compared the relative occurrence of alien aquatic plants in varying shoreline conditions modified by shoreline hardening and wave breakers. The distribution of alien aquatic species increased continually in Lake Kasumigaura over the study period, although the rate of expansion differed among years. Furthermore > 64.6% of the vegetative fragments were found within 2 km of the nearest patch. The construction of artificial wave breakers, which were installed parallel to the shoreline, had a positive influence on alien aquatic plant patch establishment. Especially, parallel wave breakers increased the patch establishment of G. spilanthoides by about 2.27-fold compared to the natural environment. Perpendicular wave breakers increased alien patch establishment by about 1.63-fold. For lakeshore management, it is important to consider both alien plant suppression and levee protection. We further suggest prompt action to prevent the expansion of alien aquatic species around pumping stations, which can also result in the relocation and expansion of invasive species.

Ecological niche modeling of Schinus molle reveals the risk of invasive species expansion into biodiversity hotspots

Abstract: Invasive species need a closer look on the threats they may cause to the environment, mainly considering the scenario of climatic changes predicted for the next decades. Schinus molle is a pioneer tree native from South America, reported as an important invasive species in four continents. Using ecological niche modeling we show that a wide area over the world is propitious for S. molle establishment under current climatic conditions, including 14 of the 25 world’s biodiversity hotspots. Current projections of climate changes suggest scenarios implying the rise of areas favorable for S. molle expansion. Therefore, particular attention should be taken in regions where it was introduced, while approaches for long-term intervention may be necessary for regions of S. molle natural occurrence if its expansion threatens other native species. However, the natural dynamic of the ecosystems should be studied and contemplated in such regions.

How traffic facilitates population expansion of invasive species along roads: The case of common ragweed in Germany

Abstract Because common ragweed (Ambrosia artemisiifolia L., henceforth Ambrosia) has negative effects on human health, it is a common focus for management, which would benefit from a better understanding of the underlying mechanisms by which the species spreads. Road systems are known to be invasion corridors, but the conduit function of vehicles for the rapid spread of Ambrosia along roads and for population extension along roadside verges has not yet been demonstrated convincingly. To quantify the effect of different traffic volumes on the dispersal and population extension of Ambrosia, we used two approaches: First, by combining field experiments along roads with records of the seed rain around single plants, we simulated a combined dispersal kernel that revealed the interactions between primary dispersal and traffic‐mediated secondary dispersal. Second, we recorded the seedling recruitment around isolated roadside populations over 2 years to determine how traffic‐related parameters affect population extension. The longest traffic‐mediated dispersal distances exceeded those of primary dispersal by about one order of magnitude. Traffic volume had a significant positive effect on dispersal distances and on the lateral deposition of seeds on the road verge. Seedling recruitment around isolated roadside populations was significantly higher in the driving direction than against, but only at the distance where the major seed rain of traffic‐mediated dispersal is to be expected according to the combined dispersal kernel (3–15 m). Synthesis and applications. This study isolates the effects of road traffic from confounding mechanisms (e.g. mowing machinery, propagule pressure from infested fields) on common ragweed (Ambrosia artemisiifolia L.) invasions. Results demonstrate the traffic‐mediated dispersal in Ambrosia invasions as a routine and predictable process that facilitates population extension in the direction of traffic along roadsides, depending on traffic volume. This highlights the importance of prioritizing mowing along high use roads and mowing of isolated populations to prevent seed abscission and further spread of common ragweed.

Methylation divergence of invasive Ciona ascidians: Significant population structure and local environmental influence.

The geographical expansion of invasive species usually leads to temporary and/or permanent changes at multiple levels (genetics, epigenetics, gene expression, etc.) to acclimatize to abiotic and/or biotic stresses in novel environments. Epigenetic variation such as DNA methylation is often involved in response to diverse local environments, thus representing one crucial mechanism to promote invasion success. However, evidence is scant on the potential role of DNA methylation variation in rapid environmental response and invasion success during biological invasions. In particular, DNA methylation patterns and possible contributions of varied environmental factors to methylation differentiation have been largely unknown in many invaders, especially for invasive species in marine systems where extremely complex interactions exist between species and surrounding environments. Using the methylation‐sensitive amplification polymorphism (MSAP) technique, here we investigated population methylation structure at the genome level in two highly invasive model ascidians, Ciona robusta and C. intestinalis, collected from habitats with varied environmental factors such as temperature and salinity. We found high intrapopulation methylation diversity and significant population methylation differentiation in both species. Multiple analyses, such as variation partitioning analysis, showed that both genetic variation and environmental factors contributed to the observed DNA methylation variation. Further analyses found that 24 and 20 subepiloci were associated with temperature and/or salinity in C. robusta and C. intestinalis, respectively. All these results clearly showed significant methylation divergence among populations of both invasive ascidians, and varied local environmental factors, as well as genetic variation, were responsible for the observed DNA methylation patterns. The consistent findings in both species here suggest that DNA methylation, coupled with genetic variation, may facilitate local environmental adaptation during biological invasions, and DNA methylation variation molded by local environments may contribute to invasion success.

Advanced Approaches to the Visualization of Data Characterizing Distribution Features of Alien Plant Species

Results of application of different approaches to the data visualization during the study of alien plant species have been analyzed and summarized, and the prospects of their use for different purposes have been evaluated. The existing experience in the study of alien plant species shows that traditional methods used to analyze their composition and distribution patterns in different regions are informative only for determining the main tendencies reflecting global processes of a phytobiota synanthropization. At the same time, new state-of-art methods are required to reveal the latent patterns of plant migration and the processes of their naturalization. The most promising approaches to analyzing large volumes of data are multivariate statistical methods. The potential of these methods is determined by their capability to identify relationships between a wide range of floristic and biological data and environmental characteristics, which can be visualized. These methods allow us to present different data in the form of diagrams reflecting interactions between individual species or whole groups of alien plants and climatic or environmental variables. They make it possible to create models of expansion of invasive species. They reflect the current statistical distances and relationships between different objects of study, which makes it possible to identify features of the group strategy of colonization of various natural and/or technogenic habitats by alien species. These strategies depend mainly on the biological characteristics of species, level of anthropogenic transformation of a regional flora, and environmental parameters.

Inter-basin water transfers and the expansion of aquatic invasive species

Inter-basin Water Transfers (IBWT) are recognized as one of the major pathways of freshwater invasion. They provide a direct link between previously isolated catchments and may modify the habitat conditions of the receiving waters such that they become more favourable for the establishment of invasive species. Combined, IBWT and invasive species will intensify the stress upon native species and ecosystems. Using the Severn and Thames Rivers –two of the largest river systems in Great Britain—as a case study, here we assess the potential influence of IBWT on the expansion of invasive species and thus their impact on biodiversity conservation. The Thames Valley is subject to extensive water abstraction, and an increasing population means that supplemented flow from the River Severn is being considered. Multi-scale Suitability Models, based on climate and water chemistry respectively, provided novel evidence that there is serious risk for further spread of invasive species in the focus area, particularly of the quagga mussel, a recent invader of the Thames River. Native freshwater mussels are particularly vulnerable to changing environmental conditions, and may suffer the decrease in alkalinity and increase in sedimentation associated with an IBWT from the lower Severn to the upper Thames. Regional models suggest considerable overlap between the areas suitable for three vulnerable native freshwater mussels and the expansion of invasive species that negatively impact upon the native mussels. This study illustrates the use of novel spatially-explicit techniques to help managers make informed decisions about the risks associated with introducing aquatic invasive species under different engineering scenarios. Such information may be especially important under new legislation (e.g. EU Invasive Species Regulation No 1143/2014) which increases the responsibility of water managers to contain and not transfer invasive species into new locations.

Niche opportunities for invasive annual plants in dryland ecosystems are controlled by disturbance, trophic interactions, and rainfall.

Resource availability and biotic interactions control opportunities for the establishment and expansion of invasive species. Studies on biotic resistance to plant invasions have typically focused on competition and occasionally on herbivory, while resource-oriented studies have focused on water or nutrient pulses. Through synthesizing these approaches, we identify conditions that create invasion opportunities. In a nested fully factorial experiment, we examined how chronic alterations in water availability and rodent density influenced the density of invasive species in both the Mojave Desert and the Great Basin Desert after fire. We used structural equation modeling to examine the direct and mediated effects controlling the density of invasives in both deserts. In the first 2 years after our controlled burn in the Great Basin, we observed that fire had a direct effect on increasing the invasive forb Halogeton glomeratus as well as a mediated effect through reducing rodent densities and herbivory. 4 years after the burn, the invasive annual grass Bromus tectorum was suppressing Halogeton glomeratus in mammal exclusion plots. There was a clear transition from years where invasives were controlled by disturbance and trophic interactions to years were resource availability and competition controlled invasive density. Similarly, in the Mojave Desert we observed a strong early influence of trophic processes on invasives, with Schismus arabicus benefitted by rodents and Bromus rubens negatively influenced by rodents. In the Mojave Desert, post-fire conditions became less important in controlling the abundance of invasives over time, while Bromus rubens was consistently benefitted by increases in fall rainfall.

Dynamic species distribution models reveal spatiotemporal habitat shifts in native range‐expanding versus non‐native invasive birds in an urban area

Urbanisation as a major driver of changes leads to the extinction of some species while others increase in abundance, especially non‐native species. Spatiotemporal distribution patterns of these successful species are likely to be shaped by their response and tolerance to urban features. This study assesses the anthropo‐ecological requirements of two co‐occurring bird species, the native range‐shifting jackdaw Corvus monedula and the non‐native invasive ring‐necked parakeet Psittacula krameri. We built yearly models over an eight‐year period using an ensemble modelling approach assessing response differences through time and between species. Predictors describing human‐made structures, socio‐ecological proxies and resources availability were extracted from temporally coincident databases. Dispersal and habitat constraints were implemented in final models to provide more realistic forecasts of species future distributions. Ensemble models evaluated with a random partition of the training dataset showed a higher accuracy than those evaluated with an independent dataset from another time period. Our results highlight temporal variations in the relative importance of predictors for both studied species. Single‐season occurrence data may thus be insufficient to characterize species ecological requirements. The ring‐necked parakeet and the jackdaw showed different responses to urban features. Jackdaws preferred the more urbanized part of the city while the distribution of parakeets was strongly positively associated with the density of exotic ornamental trees. We concluded that ring‐necked parakeet range expansion is likely to be driven by its effective ability to exploit urban resources which native species do not or under exploit, suggesting an open window of foraging opportunities. However, the jackdaw may be misled by a high cavity availability and a large amount of low‐quality anthropogenic food in the urban core. We suggest that dynamic SDMs are a critical tool not only to forecast the future expansion of invasive species but also for a better understanding of processes driving urban biodiversity persistence.

Can species distribution models really predict the expansion of invasive species?

Predictive studies are of paramount importance for biological invasions, one of the biggest threats for biodiversity. To help and better prioritize management strategies, species distribution models (SDMs) are often used to predict the potential invasive range of introduced species. Yet, SDMs have been regularly criticized, due to several strong limitations, such as violating the equilibrium assumption during the invasion process. Unfortunately, validation studies–with independent data–are too scarce to assess the predictive accuracy of SDMs in invasion biology. Yet, biological invasions allow to test SDMs usefulness, by retrospectively assessing whether they would have accurately predicted the latest ranges of invasion. Here, we assess the predictive accuracy of SDMs in predicting the expansion of invasive species. We used temporal occurrence data for the Asian hornet Vespa velutina nigrithorax, a species native to China that is invading Europe with a very fast rate. Specifically, we compared occurrence data from the last stage of invasion (independent validation points) to the climate suitability distribution predicted from models calibrated with data from the early stage of invasion. Despite the invasive species not being at equilibrium yet, the predicted climate suitability of validation points was high. SDMs can thus adequately predict the spread of V. v. nigrithorax, which appears to be—at least partially–climatically driven. In the case of V. v. nigrithorax, SDMs predictive accuracy was slightly but significantly better when models were calibrated with invasive data only, excluding native data. Although more validation studies for other invasion cases are needed to generalize our results, our findings are an important step towards validating the use of SDMs in invasion biology.

Aquatic and terrestrial morphotypes of the aquatic invasive plant, Ludwigia grandiflora, show distinct morphological and metabolomic responses.

In the context of expansion of invasive species, survival of invasive plants is conditioned by their ability to adapt. In France, the water primrose Ludwigia grandiflora, an aquatic invasive species, invades yet wet meadows, leading to a depreciation of their fodder value. Understanding its potential adaption is necessary to its management, strong differences between both morphotypes were expected. So morphological and metabolic responses to terrestrial environment were analyzed for aquatic and terrestrial morphotypes. All morphological and biomass variables were greater in the terrestrial morphotype than the aquatic morphotype, independent of conditions. In terrestrial condition, both morphotypes showed a high production of sugars in root tissues, especially in the terrestrial morphotype and both morphotypes produced a low level of amino acids in shoot tissues. All results demonstrate that the terrestrial condition seems a stressful situation for both morphotypes, which activates glycolysis and fermentation pathways to improve their survival under hypoxic stress. But, only the terrestrial morphotype has been able to adjust its metabolism and maintain efficient growth. In the future, a differential transcriptomic analysis will be carried out to confirm this result.

How global climate change and regional disturbance can expand the invasion risk? Case study of Lantana camara invasion in the Himalaya

Presently, it is debated if regional conservation efforts can alone resolve the ecological problems that global climatic changes could bring. Biological invasion is one of such concerns. In the present study, we modeled how change in global climate and regional anthropogenic pressure can impact the distribution of invasive Lantana camara in the Upper Ganga valley of the Western Himalaya (India). The forest in the study area was stratified into 1 km2 grid and two 15 m radius plot were located in each of the forest types in the grid, for recording Lantana presence. In total, 2221 plots were sampled covering 22% of forest. We used predictors representing the climate, forest patch size, fire and natural disaster variables for modeling the species distribution using maximum entropy algorithm. We further simulated 12 future landscape scenarios based on the global trends of these parameters. The present species—environment relationship was projected to these future landscape scenarios. Lantana was presently estimated to spread in 231 km2 of the study area. It invaded larger forest patches in the sub-tropical region, and smaller disturbed forest patches in the warm and cold temperate region. Increased distribution of Lantana was projected across all the future scenarios. The study revealed how global climate changes and regional anthropogenic pressure can have a synergistic effect on the expansion of invasive species in the future. It thus questions the efficiency of conducting only regional efforts in absence of global initiative to reduce the greenhouse gases emission.

Sex‐specific shifts in morphology and colour pattern polymorphism during range expansion of an invasive lizard

AbstractAimHuman‐assisted range expansion of animals to new environments can lead to phenotypic shifts over ecological time‐scales. We investigated whether phenotypic changes are sex‐specific using an invasive lizard (Lampropholis delicata).LocationPacific region (Hawaiian Islands, Lord Howe Island, New Zealand, eastern Australia).MethodsUsing our knowledge of the introduction history of L. delicata, we examined museum specimens of individuals collected across the native and introduced range to determine whether shifts in morphology or colour pattern polymorphism had occurred during its range expansion, and if so, whether they differed between the sexes.ResultsSexual dimorphism in both size and shape was documented within the native range of the delicate skink. However, during range expansion, phenotypic shifts were observed in shape, but not size. In two of the three invasive populations, these phenotypic shifts were sex‐specific. In the Hawaiian Islands, changes in shape were driven by males, whereas in New Zealand it was due to shifts in females. Similarly, changes in the frequency of a colour pattern polymorphism, a mid‐lateral stripe shown to have sex‐specific impacts on fitness (positive in females, negative in males), occurred following colonization of the Hawaiian Islands and Lord Howe Island. In Hawaii, the incidence of the polymorphism increased over time in females, and decreased in males.Main conclusionsPhenotypic shifts during the range expansion of invasive species may be sex‐specific, and are potentially related to the degree of realized niche shift that has occurred between the source and introduced range.