Early Detection Of Invasive Species Research Articles

Catching invasives with curiosity: the importance of passive biosecurity surveillance systems for invasive forest pest detection.

First detections of nonnative insect species are often made by curious members of the public rather than by specialists or trained professionals. Passive surveillance is a crucial component of national biosecurity surveillance, highlighted by early detection case studies of several prominent nonnative arthropod pests (e.g., Asian longhorned beetle [ALB], Jorō spider, spotted lanternfly). These examples demonstrate that curiosity and the recognition of novelty in the natural world, along with enabling technology and systems, are a critical part of early detection and effective invasive species management. This is particularly impactful when dealing with conspicuous pests or for new and emerging nonnative species that have yet to be detected in a new location. Data from historical and recent accounts of first detections of ALB incursions and other invasive forest pests underscore the need to invest in passive surveillance reporting systems and fully integrate public observations into existing surveillance frameworks. New automated approaches streamline the assessment of public observations and can generate pest alerts to initiate a formal regulatory assessment. Biodiversity monitoring platforms, such as iNaturalist, provide a focal point for community engagement and aggregate verified public observations. Empowering proactive reporting of biological novelty provides needed support for early detection of invasive species. Embracing the public as active members of the surveillance community can be cost effective and lead to the greatest gains in the proactive management of invasive species around the world.

New dockside eDNA based protocol to detect the seaweed Asparagopsis armata evaluated by stakeholders

Early detection of invasive species is crucial to deal effectively with biological invasions in ports, which are hotspots of species introductions. In this study, a simplified end-time PCR methodology conducted on eDNA from water samples was developed for rapid detection of the invasive seaweed Asparagopsis armata (four hours from water collection to result visualization). It was tested dockside in four international Spanish ports in presence of stakeholders, whose feedback was obtained to explore the real applicability of this biotechnology. Although biological invasions were not a main concern for them, results indicate a unanimous approval of the methodology by the stakeholders, having detected the presence of A. armata in three of the ports. Stakeholders suggested further developments for easier application of the tool and multiple species detection, to be adopted for the control of invasive species in ports.

Distribution of the Cannabis sativa L. in the Western Himalayas: A tale of the ecological factors behind its continuous invasiveness

The invasion of species in new regions depends on multiple factors, especially, the prevailing environmental factors. The environmental conditions are essential to understand for planning effective management strategies related to invasive species. Little is known about Cannabis as an established invasive weed. We hypothesized that the successful establishment of this invading species is influenced by the environmental variables; however, some of them have a much stronger influence than the others. Quantitative ecological methods were adopted for sampling the habitats invaded by Cannabis sativa, in a total of 165 quadrats. Soil samples were collected for soil analyses from each of those quadrat. Ecological and statistical approaches including Structure Equation Modeling (SEM) procedures were applied to evaluate the impact of environmental factors, ecological interrelationships, and the resultant invasiveness of the C. sativa. Our findings indicate that elevation, temperature, humidity, anthropogenic pressure, physio-chemical prperties of soil and habitat degradation play significant roles in determining the distribution and abundance of C. sativa. Principal Component Analysis (PCA) of the parameters further clarifies that elevation is the most important driver in explaining the successful establishment of the invader species with a 30.1% variance. Structural equation modeling further confirms the significant role played by elevation, which not only directly affects the abundance of Cannabis but also indirectly influences other variables such as anthropogenic pressure, temperature, and humidity etc. However, the invasion of C. sativa is less affected by soil saturation pH, electrical conductivity, phosphorous, potassium, and CaCO3. Our study provides valuable scientific information that could be used for the early detection of invasive species at the early stage of invasion and in devising policies for their management and control.

Incursion Preparedness, Citizen Science and Early Detection of Invasive Insects: The Case of Aleurocanthus spiniferus (Hemiptera, Aleyrodidae) in France.

We describe the process by which the quarantine whitefly, Aleurocanthus spiniferus (Hemiptera, Aleyrodidae), was detected in France. The initial observation was made by a volunteer who reported a picture of an adult in the Inventaire National du Patrimoine Naturel (INPN Espèces), a citizen science resource developed by l'Office Français de la Biodiversité and the French Muséum National d'Histoire Naturelle. The specimen was suspected to be A. spiniferus from this picture by one of the expert entomologists in charge of the Hemiptera group validation. Once the species was identified, it was mounted on a slide and the information was officially passed on to the ministry in charge of agriculture via a communication channel set up in advance for this type of situation. The ministry then triggered the regulatory actions planned in the event of the suspected detection of quarantine organisms. Sampling was quickly carried out and the specimens collected on this occasion were formally identified as belonging to the species A. spiniferus. This led to the formalization of an outbreak in France. This sequence of decisions took just two months from the first observation to the implementation of a management plan. This case presents how incursion preparedness contributes to a rapid response. Furthermore, this case exemplifies how citizen science can contribute to the early detection of invasive species and highlights the importance of informing both the general public and professionals about major environmental issues.

Predicting the spatio-temporal pattern of range expansion under lack of equilibrium with climate

Early detection of invasive species in regions under threat is key for biodiversity conservation. Here we conduct a retrospective study to assess whether correlative Species Distribution Models (SDMs) can predict the spatio-temporal range of expansion in an invasive species, the Asian hornet. Given that modelling invasive species distributions defies one of the main assumptions of SDMs, the equilibrium with climate, we also introduce a quantitative assessment of climatic disequilibrium in the invaded area based on hypervolume comparison between the native and invaded areas (both unoccupied and occupied territories). We evaluate the ability of three different modelling approaches (presence-only, presence-background and presence-absence) calibrated with data until 2013 to predict the species distribution observed the following years (2015, 2017, 2019, and 2021). Our results show that presence-only models based on the BIOCLIM algorithm can effectively predict the spatio-temporal pattern of invasion when predictions are rescaled based on percentiles (i.e. ranked suitability) and the model is calibrated with data from both native and invaded areas. These models predicted higher suitability values for sites that were invaded earlier in time and, importantly, they did not predict low suitability values for sites that were eventually occupied years later. Thus, they can be very useful for decision-makers and managers, as they provide a probabilistic prediction of both (i) the temporal dimension of species range expansion, and (ii) the potential distribution range in the long term. Such information would allow prioritizing monitoring efforts in the short term without losing sight of the potential risks in the long term.

Combining multiple markers significantly increases the sensitivity and precision of eDNA‐based single‐species analyses

AbstractThe analysis of environmental DNA (eDNA) is becoming integrated as an established biomonitoring tool, often characterized by detection limits exceeding those of conventional counterparts. However, further improving the sensitivity of these methods may be invaluable for the early detection of invasive species, or for locating remnant populations of endangered species, and the adequate quantification of their abundances. In this study, we provide empirical evidence showing that the implementation of multiple genetic markers targeting different loci is a surprisingly overlooked strategy to increase the sensitivity of single‐species detections and quantification of their abundance, particularly at the lower end of the species abundance range. We analyzed 45 natural eDNA samples obtained from a wide range of water bodies in Belgium, in which either the invasive American bullfrog (Lithobates catesbeianus) or the rare European weather loach (Misgurnus fossilis) occurred under variable abundances, and compared detection success and precision of quantification of simplex (single locus) versus multiplex (multilocus) droplet digital PCR (ddPCR) analyses. Multiplexing different primer/probe assays targeting independent loci resulted in a significantly enhanced detection probability compared to the simplex analyses, gaining a twofold reduction in the limit of detection (LOD). Also the precision of eDNA quantification significantly improved in multiplex reactions, especially in low concentration samples. This was reflected in a significant reduction in the coefficient of variation (CV) among technical replicates, resulting in an associated decrease of the limit of quantification (LOQ). We conclude that the use of multiple markers can significantly improve the analytical sensitivity of eDNA‐based single‐species detections and precision of absolute abundance quantifications.

Incidental invertebrate‐derived DNA detection of invasive and threatened species in temperate dry Southeast Australian forest

AbstractWell‐informed biodiversity conservation practice can often be precluded by poor species detectability. For example, populations being missed during surveys can lead to them being omitted from species lists or area management plans. iDNA (invertebrate‐derived DNA) is a recently developed set of techniques for improving the detectability of elusive vertebrates by exploiting their associated invertebrates. Parasitic and scavenging invertebrates can be readily collected, and their gut contents DNA barcoded to detect local vertebrate diversity. However, most iDNA surveys have targeted mammals and have been carried out in tropical areas and/or rainforests. We carried out iDNA surveys targeting frogs in temperate dry sclerophyll forests in south‐eastern Australia. We set mosquito traps broadcasting recorded frog calls with the aim of collecting frog‐biting flies, which are attracted to frog calls. We collected 156 fly specimens, although none were of frog‐biting species, and no frogs were detected via iDNA, despite many being observed in the field. However, two mammal and one reptile species were detected via iDNA: the feral cat (Felis catus: Felidae), domestic dog or dingo (Canis lupus: Canidae) and the threatened Rosenberg's monitor (Varanus rosenbergi: Varanidae). Vertebrate‐sampling flies are likely highly abundant in the area since they were collected apparently incidentally in traps lacking appropriate attractants; a promising result for further surveys is different attractants are employed. This study is one of the few in which an invasive species has been detected through iDNA, and highlights its potential for improved detectability of threatened species outside of the tropics and early detection of invasive species.

Undetected but Widespread: the Cryptic Invasion of Non-Native Cattail (Typha) in a Pacific Northwest Estuary

The early detection of invasive species is an important predictor of management success. Non-native narrow-leaved cattail (Typha angustifolia) has been detected in the Fraser River Estuary (FRE) in recent decades, but questions around their degree of establishment, and the potential emergence of hybrid cattail (Typha × glauca), remain unanswered. This study models the current and potential future distribution of non-native cattail in the FRE using a combination of spectral imagery analysis and species distribution modeling. Contrary to our expectation, we find that non-native cattails are widespread, currently occupying approximately 4 or 50 ha of FRE tidal marshes. Though never formally recorded in the estuary previously, T. × glauca appears to be the more abundant taxon, suggesting heterosis may be facilitating this invasion. We describe these taxa as cryptic invasive species, as their resemblance to native cattail (Typha latifolia) likely inhibited their detection. In our species distribution model, we distinguish between site suitability (ability to establish and persist) and susceptibility (risk of colonization when suitable). Our model predicts the scale of this invasion may increase over time, as 29% and 20% of the estuary has moderate or high suitability and susceptibility probabilities, respectively, while 16% and 24% of these habitats are currently occupied. Estuary-wide containment and eradication are unlikely given the extent of this invasion. Consequently, we recommend management prioritize monitoring and early eradication in areas of high conservation and cultural value. This study highlights the vulnerability of estuaries to cryptic invasions and the invasibility of Pacific Northwest estuaries by non-native cattail.

Assessing the Efficacy of Phenological Spectral Differences to Detect Invasive Alien Acacia dealbata Using Sentinel-2 Data in Southern Europe

Invasive alien plants are transforming the landscapes, threatening the most vulnerable elements of local biodiversity across the globe. The monitoring of invasive species is paramount for minimizing the impact on biodiversity. In this study, we aim to discriminate and identify the spatial extent of Acacia dealbata Link from other species using RGB-NIR Sentinel-2 data based on phenological spectral peak differences. Time series were processed using the Earth Engine platform and random forest importance was used to select the most suitable Sentinel-2 derived metrics. Thereafter, a random forest machine learning algorithm was trained to discriminate between A. dealbata and native species. A flowering period was detected in March and metrics based on the spectral difference between blooming and the pre flowering (January) or post flowering (May) months were highly suitable for A. dealbata discrimination. The best-fitted classification model shows an overall accuracy of 94%, including six Sentinel-2 derived metrics. We find that 55% of A. dealbata presences were widely widespread in patches replacing Pinus pinaster Ait. stands. This invasive alien species also creates continuous monospecific stands representing 33% of the presences. This approach demonstrates its value for detecting and mapping A. dealbata based on RGB-NIR bands and phenological peak differences between blooming and pre or post flowering months providing suitable information for an early detection of invasive species to improve sustainable forest management.

Round Goby Detection in Lakes Huron and Michigan—An Evaluation of eDNA and Fish Catches

Aquatic surveys for fish in large water bodies (e.g., Laurentian Great Lakes of North America) often require a flexible approach using multiple methods, surveying different depths, and sampling across seasons, especially when the target species is elusive in its natural habitat. The round goby (Neogobius melanostomus) is an invasive, bottom-dwelling fish inhabiting rocky areas of all five Great Lakes. While trawl surveys are typically used for abundance assessments, angling has been demonstrated as a means of supplementing surveys with additional data. Yet, round goby abundance and distribution is still not well described. Recently, with considerable success, scientists have explored sampling environmental DNA (eDNA) to complement traditional monitoring techniques for population abundance estimates, early detection of invasive species, and spawning or migration events. Therefore, we collected eDNA from water samples alongside bottom trawls and hook and line angling in Lakes Huron and Michigan to detect round goby. eDNA samples were analyzed by both droplet digital PCR (ddPCR) and quantitative PCR (qPCR) to maximize the likelihood of detection. Overall, round goby was captured in 23% of the trawls, but the eDNA based methods detected round goby in 74% and 66% of samples by ddPCR and qPCR, respectively, mostly in samples collected at <30 m depths, and mostly in the fall. More studies comparing eDNA based methods to traditional monitoring, especially trawls in large open waters, may contribute to a better understanding of using eDNA in population assessments.

Integrating invasive species risk assessment into environmental DNA metabarcoding reference libraries.

Environmental DNA (eDNA) metabarcoding has shown promise as a tool for estimating biodiversity and early detection of invasive species. In aquatic systems, advantages of this method include the ability to concurrently monitor biodiversity and detect incipient invasions simply through the collection and analysis of water samples. However, depending on the molecular markers chosen for a given study, reference libraries containing target sequences from present species may limit the usefulness of eDNA metabarcoding. To explore the extent of this issue and how it may be resolved to aid biodiversity and invasive species early detection goals, we focus on fishes in the well-studied Laurentian Great Lakes region. First, we provide a synthesis of species currently known from the region and of non-indigenous species identified as threats by international, national, regional, and introduction pathway-specific fish risk assessments. With these species lists, we then evaluate 23 primer pairs commonly used in fish eDNA metabarcoding with available databases of sequence coverage and species specificity. Finally, we identify established and potentially invasive non-indigenous fish that should be prioritized for genetic sequencing to ensure robust eDNA metabarcoding for the region. Our results should increase confidence in using eDNA metabarcoding for fisheries conservation and management in the Great Lakes region and help prioritize reference sequencing efforts. The ultimate utility of eDNA metabarcoding approaches will come when conservation management of existing fish communities is integrated with early detection efforts for invasive species surveillance to assess total fish biodiversity.

Policy action needed to unlock eDNA potential

Policy action needed to unlock <scp>eDNA</scp> potential

Challenges in eDNA detection of the invasive European green crab, Carcinus maenas

The early detection of invasive species is essential to cease the spread of the species before it can cause irreversible damage to the environment. The analysis of environmental DNA (eDNA) has emerged as a non-harmful method to detect the presence of a species before visual detection and is a promising approach to monitor invasive species. Few studies have investigated the use of eDNA for arthropods, as their exoskeleton is expected to limit the release of eDNA into the environment. We tested published primers for the invasive European green crab, Carcinus maenas, in the Gulf of Maine and found them not species-specific enough for reliable use outside of the area for which they were designed for. We then designed new primers, tested them against a broad range of local faunal species, and validated these primers in a field study. We demonstrate that eDNA analyses can be used for crustaceans with an exoskeleton and suggest that primers and probe sequences must be tested on local fauna at each location of use to ensure no positive amplification of these other species.

Reinforcement of Environmental DNA Based Methods (Sensu Stricto) in Biodiversity Monitoring and Conservation: A Review.

Simple SummaryWorldwide biodiversity loss points to a necessity of upgrading to a fast and effective monitoring method that can provide quick conservation action. Newly developed environmental DNA (eDNA) based method found to be more cost-effective, non-invasive, quick, and accurate than traditional monitoring (spot identification, camera trapping). Although the eDNA based methods are proliferating rapidly, as a newly developed branch, it needs more standardization and practitioner adaptation. The present study aims to evaluate the eDNA based methods, and their potential achievements in biodiversity monitoring, and conservation for quick practitioners’ adaption. The investigation shows that the eDNA technique is applicable largely in (i) early detection of invasive species, (ii) species detection for conservation, (iii) community-level biodiversity monitoring, (iv) ecosystem health monitoring, (v) study on trophic interactions, etc. Thus, the eDNA technique shows a great promise with its high accuracy and authenticity, and will be applicable alone or alongside other methods in the near future.Recently developed non-invasive environmental DNA-based (eDNA) techniques have enlightened modern conservation biology, propelling the monitoring/management of natural populations to a more effective and efficient approach, compared to traditional surveys. However, due to rapid-expansion of eDNA, confusion in terminology and collection/analytical pipelines can potentially jeopardize research progression, methodological standardization, and practitioner adoption in several ways. Present investigation reflects the developmental progress of eDNA (sensu stricto) including highlighting the successful case studies in conservation management. The eDNA technique is successfully relevant in several areas of conservation research (invasive/conserve species detection) with a high accuracy and authentication, which gradually upgrading modern conservation approaches. The eDNA technique related bioinformatics (e.g., taxon-specific-primers MiFish, MiBird, etc.), sample-dependent methodology, and advancement of sequencing technology (e.g., oxford-nanopore-sequencing) are helping in research progress. The investigation shows that the eDNA technique is applicable largely in (i) early detection of invasive species, (ii) species detection for conservation, (iii) community level biodiversity monitoring, (iv) ecosystem health monitoring, (v) study on trophic interactions, etc. Thus, the eDNA technique with a high accuracy and authentication can be applicable alone or coupled with traditional surveys in conservation biology. However, a comprehensive eDNA-based monitoring program (ecosystem modeling and function) is essential on a global scale for future management decisions.

Mapping the Extent of Invasive Phragmites australis subsp. australis From Airborne Hyperspectral Imagery

Invasive species pose one of the greatest threats to global biodiversity. Early detection of invasive species is critical in order to prevent or manage their spread before they exceed the ability of land management groups to control them. Optical remote sensing has been established as a useful technology for the early detection and mapping of invasive vegetation populations. Through the use of airborne hyperspectral imagery (HSI), this study establishes a target detection methodology used to identify and map the invasive reed Phragmites australis subsp. australis within the entire extent of Îles-de-Boucherville National Park (Quebec, ON, Canada). We applied the Spectral Angle Mapper (SAM) target detection algorithm trained with a high accuracy GNSS ground truth data set to produce a park-wide map illustrating the extent of detected Phragmites. The total coverage of detected Phragmites was 26.74 ha (0.267 km2), which represents 3.28% of the total park area of 814 ha (8.14 km2). The inherent spatial uncertainty of the airborne HSI (∼2.25 m) was accounted for with uncertainty buffers, which, when included in the measurement of detected Phragmites, lead to a total area of 59.17 ha (0.591 km2), or 7.26% of the park. The overall accuracy of the Phragmites map was 84.28%, with a sensitivity of 76.32% and a specificity of 91.57%. Additionally, visual interpretation of the validation ground truth dataset was performed by 10 individuals, in order to compare their performance to that of the target detection algorithm. The overall accuracy of the visual interpretation was lower than the target detection (i.e., 69.18%, with a sensitivity of 59.21% and a specificity of 78.31%). Overall, this study is one of the first to utilize airborne HSI and target detection to map the extent of Phragmites over a moderately large extent. The uses and limitations of such an approach are established, and the methodology described here in detail could be adapted for future remote sensing studies of Phragmites or other vegetation species, native or invasive, at study sites around the world.

Recent advances in environmental DNA‐based biodiversity assessment and conservation

Recent advances in environmental DNA‐based biodiversity assessment and conservation

INVASION OF SAVANNAS BY PROSOPIS TREES IN EASTERN AFRICA: EXPLORING THEIR IMPACTS ON LULC DYNAMICS, LIVELIHOODS AND IMPLICATIONS ON SOIL ORGANIC CARBON STOCKS

Abstract. Trees of the genus Prosopis from the Americas, were introduced in Eastern Africa in the 1970s to mitigate land degradation and its associated disservices. However, over time these trees have spread and invaded valuable grasslands and croplands and consequently led to significant land use and land cover (LULC) changes and livelihood stress. Early detection of invasive species is essential for formulating effective management strategies to prevent further spread into non-invaded lands and for monitoring the outcome of management interventions. We mapped the spatio-temporal evolution and dynamics of Prosopis invasion, its impacts on LULC and livelihoods in Baringo, Kenya by applying a Random Forest classifier on Landsat satellite data over seven-year intervals from 1988 – 2016. We then linked the LULC changes to soil organic carbon (SOC) stocks that we had measured for the different LULCs and also to socio-economic data on annual costs of clearing Prosopis from farmlands. By 2016, Prosopis had invaded 18,792 ha of land, spreading at a rate of 640 ha/yr, while all other land uses and land cover declined, each by over 40% of its original coverage in 1988. Through LULC specific SOC measurements, and relating the changes to annual costs of clearing Prosopis, we found that Prosopis removal and restoration to grassland is more effective for climate change mitigation compared to Prosopis “cultivation” while also avoiding trade-offs with other ecosystem services and livelihoods. Therefore, future management of this species in Kenya and Eastern Africa should be based on a more collaborative and integrated approach.

Matching a snail's pace: successful use of environmental DNA techniques to detect early stages of invasion by the destructive New Zealand mud snail.

Early detection of invasive species allows for a more rapid and effective response. Restoration of the native ecosystem after an invasive population has established is expensive and difficult but more likely to succeed when invasions are detected early in the invasion process. Containment efforts to prevent the spread of known invasions also benefit from earlier knowledge of invaded sites. Environmental DNA (eDNA) techniques have emerged as a tool that can identify invasive species at a distinctly earlier time point than traditional methods of detection. Here, we focus on whether eDNA techniques can be successfully applied to detect new invasions by the destructive New Zealand Mud Snail Potamopyrgus antipodarum (NZMS). It is an opportune time to apply eDNA-based detection in P. antipodarum, which is currently expanding its invasive range across eastern North America. We collected water samples from eight sites in central Pennsylvania that prior evidence indicated were not yet invaded by the NZMS but were part of the same watershed as other previously documented invaded sites. We found evidence for NZMS invasion at five of the eight sites, with subsequent physical confirmation of mud snails at one of these sites. This study is the first example of successful application of eDNA to detect a previously unidentified invasive population of NZMS, setting the stage for further monitoring of at-risk sites to detect and control new invasions of this destructive snail. This study also shows potential opportunities for invasion monitoring offered by using low-cost efforts and methods that are adaptable for citizen science.

Outreach increases detections of an invasive species in a crowdsourced monitoring program

Crowdsourcing can be a useful tool for the early detection of invasive species. Invasive wild pigs (Sus scrofa) have been reported in Ontario, Canada. We compared trends in reporting frequency of wild pig sightings to trends in media events that included directions for the public on where to submit their wild pig sightings. We found that media events occurring on the same week, and in up to two weeks before the sighting was reported significantly increased the number of wild pig reports we received. Our findings suggest that media can be used to increase participation by the public. Because of this relationship, our findings also imply that reporting frequency alone cannot accurately index real changes in wild pig numbers—participants were more likely to report sightings after they had been exposed to relevant media, and spikes in the number of reports tracked our outreach efforts. Despite this limitation, reports of wild pig sightings from community members remain a cost-effective tool to detect low-density invasive species across large regions, and participation in the program can be increased with periodic news media and social media blitzes.

The first detection of the fungal pathogen batrachochytrium dendrobatidis in Norway with no evidence of population declines for great crested and smooth newts based on modeling on traditional trapping data

AbstractThe pathogenic fungus Batrachochytrium dendrobatidis (Bd) causes chytridiomycosis in amphibians across the world, often leading to population declines and species extinctions. Here, we present the first detection of Bd in Norway, diagnosed using environmental DNA (eDNA) in water samples. In a genetic screening of 31 ponds in southeastern Norway for Bd, great crested newt (Triturus cristatus) and smooth newt (Lissotriton vulgaris), we detected Bd in five different localities. Resampling in one location revealed that time of sampling seemingly had a strong effect on the concentration of Bd eDNA in the water, which increased from May till June. In contrast, eDNA concentration of great crested newt decreased during the same period. Following a traditional sampling approach with traps, newts in the investigated ponds have been sampled for population estimates since 2012. We imposed a model on the catch data and contrasted the Bd‐positive ponds to the Bd‐negative ponds, finding no signs of population declines in the Bd‐positive ponds. This could suggest either recent infection events, with animals still having low prevalence of Bd and with little time for Bd to affect the present breeding generations of newts, and/or that the two newt species are infection‐tolerant. This study further highlights eDNA as a tool for early detection of invasive species.