Guest blog post by Arnold Erdélyi, Judit Hartdégen, Ákos Malatinszky, and Csaba Vadász
Today, almost everyone is familiar with the term “biological invasion”. Countless studies have been carried out to describe the various processes, and explore the cause and effect, and several methods have been developed in order to control certain invasive species. However, one of the biggest puzzles is always the question of how it all happened. It is not always easy to answer, and, in general, the smaller the area, the more difficult or even impossible it is to answer. In the course of our work, we attempted to explore the history of the spread of four, non-indigenous invasive tree species in one of the most important Hungarian forest-steppe forests of high conservation value, the Peszér Forest (approximately 1000 ha). Last week, we published our study in the journal One Ecosystem.
The Far Eastern tree of heaven (Ailanthus altissima), as well as the North American black cherry (Prunus serotina), the box elder (Acer negundo) and the common hackberry (Celtis occidentalis) are among the worst invasive plant species in Hungary. They are also responsible for serious conservation and economic problems in the Peszér Forest.
Invasion of tree of heaven (top left) and common hackberry (top right) in poplar stands, carpet of seedlings of black cherry (bottom left), and monodominant stand of box elder, regrown from stump after cutting (bottom right)
Historical reconstructions of the spread of invasive species are most often based on only one, or sometimes a few aspects. We used six approaches simultaneously:
we reviewed the published and grey literature,
extracted tree species data from the National Forest Database since 1958,
conducted a field survey with full spatial coverage (16,000 survey units (25×25 m quadrats)) – instead of sampling,
recorded all the largest (and presumably the oldest) individuals for annual ring counts,
performed hotspot analyses on the field data
collected local knowledge.
Cutting down the oldest common hackberry trees in order to count the annual rings from trunk discs
Our results show that each approach provided some new information, and without any of them the story revealed would have been much shorter and more uncertain. We have also highlighted that at the local level, the use of one or two aspects can be not only inadequate but also misleading.
From the literature it was possible to determine the exact place and date of the first occurrence of the tree of heaven and the black cherry. However, in the case of black cherry, for example, it was only possible to piece together the circumstances of the first plantings by combining three different sources. The first occurrences of box elder were found in forestry data. Finally, in the case of the common hackberry, searching for old individuals and determining their age gave the best results.
Common hackberry in the Peszér forest according to the recent forestry data (2016) and the field survey (2017-2019). The difference is clear: in the official forestry database, the tree species is underrepresented several times over
A well-explored story of a biological invasion can go a long way in making more and more people understand that controlling these non-indigenous species can only be beneficial. On the other hand, it can also help to strengthen conservation efforts, for example by increasing the volunteer workforce, which can be a major factor in the reduction of certain species. We hope that our work and the approaches we have taken will serve as a good model for exploring other invasion stories around the world.
Winter snapshot from the Peszér Forest, a diverse forest edge habitat along an inner road.
Erdélyi A, Hartdégen J, Malatinszky Á, Vadász C (2023) Historical reconstruction of the invasions of four non-native tree species at local scale: a detective work on Ailanthus altissima, Celtis occidentalis, Prunus serotina and Acer negundo. One Ecosystem 8: e108683. https://doi.org/10.3897/oneeco.8.e108683
Hundreds of weeds have been found advertised on a public online marketplace in Australia. Cacti and pond plants were among the most frequently advertised illegal weed species. These weeds are prohibited in Australia due to their harmful impact on the country’s environment and agriculture. Despite this, a research team led by Jacob Maher discovered thousands of online advertisements for these weeds. Their study is published in the open access journal NeoBiota.
Water hyacinth, a notorious invader that was found traded online.
Trade of ornamental plants, the kind grown in homes and gardens, is the major way weeds are introduced to new places. Some ornamental plants can make their way into the environment and become invasive, negatively impacting native species and agriculture. Increasingly, plants are traded on the internet, allowing a wide variety of plants to be introduced to more distant places. A lack of surveillance and regulation of this trade has resulted in the wide trade of invasive species.
In response, scientists from the University of Adelaide have utilised specialised software called ‘web scrapers’ to monitor trade on public classifieds websites. These web scrapers automate the collection of online advertisements. This allowed the researchers to detect thousands of advertisements for weeds over a 12-month period.
Opuntia, a notorious invader that was found traded online.
Despite Australia’s laws banning the trade of harmful weeds, advertisements were observed across the country. Some of the weeds advertised were associated with uses by traders, including food and medicine. The most popular uses were associated with pond and aquarium plants such as filtering water and providing fish habitat.
The researchers recommend that governments adopt web scraping technology to assist in regulating online trade of plants. They also highlight increasing public awareness and seeking cooperation from online marketplaces as solutions to this growing problem.
“Currently, these online marketplaces allow people to advertise and purchase invasive species, whether they are aware of it or not,” says Maher. “Regulation is needed, but we also need to cultivate awareness of amongst plant growers of this issues and we need help from marketplaces to regulate trade on their end.”
The technology developed in this study is now being utilised by biosecurity agencies in Australia to monitor and regulate the illegal trade of plants and animals online.
Armored catfish (Pterygoplicthys spp.) and microplastics, as invasive species and emerging contaminants, respectively, represent two socio-environmental problems in the globalized world, since both have negative effects on faunistic communities and freshwater habitats, as well as on rural community fisheries and public health.
Non-native invasive species of armored catfish have become numerically dominant in some ecosystems, with efforts to eradicate them a seemingly endless task. Due to this, a possible scenario of biological homogenization in Mesoamerica can be expected, mainly given by the wide dispersion of the Pterygoplichthys species, added to the introduction of other non-native catfish species.
Photo: Miguel Ángel Salcedo. Drawing: Diana Ríos-Hernández.
The omnipresence of plastics in terrestrial and aquatic environments is caused by their excessive use and inadequate management of waste. The discarded plastics are fragmented, degraded, and dissolved by solar radiation, wind, and water, among other agents, to be incorporated into the food web in aquatic environments.
Microplastics found in the digestive tract of armed catfish (Pterygoplichthys spp.)
Both persist in the aquatic environment, microplastics forming the disproportionate amount of plastic garbage, and catfish thanks to their tolerance to pollution and anoxic environments, and their ability to survive for several hours breeding atmospheric oxygen. What is the relationship between the two? Microplastics, depending on their origin and composition, are sedimented in the wetlands, where they can be ingested by detritus feeders, such as armored catfish, mainly in areas where there is runoff or discharge of liquid waste.
In this context, we ask ourselves, can armored catfish be used as biomonitors of microplastics deposited in wetlands? Taking the above into consideration, the doctoral student Gabriela Angulo-Olmos under the guidance of the researchers Nicolás Álvarez-Pliego, Alberto J. Sánchez, Rosa Florido, Miguel Ángel Salcedo, Allan K. Cruz-Ramírez and Arturo Garrido Mora from the Laboratorio de Humedales, from the División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, decided to answer the aforementioned question based on the numerical dominance of armored catfish recorded in the aquatic ecosystems of the Metropolitan Area of Villahermosa (MAV) in the coastal plain of the Gulf of Mexico.
A) Study area; Metropolitan Area of Villahermosa. Map modified from INEGI (2021). B) La Pólvora lake (Satélite Airbus 2023).
The stomach contents of the specimens from a lake located in the MAV were reviewed and the results showed that all the specimens had consumed microfibers. This result corroborated that these organisms can ingest sedimented microplastics due to their benthophagous habits.
The use of armored catfish as a resource in the food industry has had positive results, but is still insufficient. Therefore, we propose that another option to control their populations is to subtract and use this organism to verify which are the most frequent and abundant emerging contaminants deposited in the bottoms of urban wetlands.
Angulo-Olmos G, Alvarez-Pliego N, Sánchez AJ, Florido R, Salcedo MÁ, Garrido-Mora A, Cruz-Rámirez AK (2023) Microfibers in the gut of invasive armored catfish (Pterygoplichthys spp.) (Actinopterygii: Siluriformes: Loricariidae) in an urban lake in the floodplain of the Grijalva River basin, Mexico. Acta Ichthyologica et Piscatoria 53: 81–88. https://doi.org/10.3897/aiep.53.102643
“Stomp, squash, smash” has been the accompanying soundtrack to the expansion of an odd-looking bug through the Eastern US. The spotted lanternfly, a large planthopper native to Asia, has been popularized in media outlets as the most recent enemy one ought to kill on sight.
Spotted lanternflies. Photo by Matthew Helmus
This charismatic insect was first discovered in the US in Berks county, Pennsylvania, in 2014, likely the result of an accidental introduction alongside shipments of landscaping materials. Since then, the invasive pest has spread throughout the country, fueled by its ability to hitch rides undetected on cargo and passenger vehicles, and aided by the widespread presence of one of its favorite food sources, the tree of heaven, another invasive in North America. As of 2023, it has been found in 14 US states.
Unfortunately, this species is not picky when it comes to the plants it consumes, favoring both crops and ornamentals, and showing a particular preference for cultivated grape. This dietary choice has impacted several wine-making areas throughout Pennsylvania and New York state, and is threatening important wine hubs on the Western coast of the US.
When it comes to controlling the spread of this pest, two of the main challenges for researchers and field managers alike are to 1) know where this species is today so that eradication campaigns can be targeted and 2) predict where it will be tomorrow, to invest in prevention practices. Both efforts rely on accurate and extensive knowledge of its past and present distribution.
Many state and federal agencies, as well as individual research institutions, have been involved in conducting surveys to detect this bug in the field. In addition, a campaign to raise public awareness has fostered the development of self-reporting tools citizens can use to track sightings of this insect. Unfortunately, given the different practices adopted by these parties, the data on the presence of spotted lanternfly are scattered and hard to access, which makes it harder to assess and manage its spread.
Spotted lanternflies. Photo by Matthew Helmus
The need to put together a current, comprehensive, consistent and openly available dataset pushed researchers at Temple University to take action. A research group led by Dr. Matthew Helmus has been closely monitoring the spread of this invasive pest since its inception, contacting institutions and collecting data. In a recent work published in the journal NeoBiota, Dr. Helmus and Dr. Sebastiano De Bona, together with collaborators across several agencies, put together an anonymized and comprehensive dataset that collected all records of spotted lanternfly in the US to date. These records come from a plethora of sources, from control actions, citizen-science projects, and research efforts. The resulting dataset contains highly detailed data (at 1 km2 resolution) with yearly information on the presence or absence of spotted lanternflies, the establishment status of this pest, and estimated population density, across over 650,000 observations.
“The lydemapr package will aid researchers, managers and the public in their understanding, modelling and managing of the spread of this invasive pest,” says Dr. De Bona, the lead author of the study.
The scientists hope that this package will make forecasting the spread of the spotted lanternfly easier and foster more effective collaboration between agencies and researchers.
De Bona S, Barringer L, Kurtz P, Losiewicz J, Parra GR, Helmus MR. 2023. lydemapr: an R package to track the spread of the invasive Spotted Lanternfly (Lycorma delicatula, White 1845)(Hemiptera, Fulgoridae) in the United States. NeoBiota 85: 151–168, DOI: 10.3897/neobiota.86.101471
Plant species become exotic after being accidentally or deliberately transported by humans to a new region outside their native range, where they establish self-perpetuating populations that quickly reproduce and spread. This is a complex process mediated by many factors, such as plant traits and genetics, which challenges the creation of general guidelines to predict or manage plant invasions. Scientists from Spanish and Australian institutions have now defined a new framework to find the predictors of invasiveness, investigating species that have succeeded or failed to establish abroad after following similar historical introduction routes.
Ancient agricultural landscape dominated by plant species introduced in other Mediterranean regions (Parque Natural de Los Alcornocales, Andalucía, Spain). Photo by Dr Javier Galán Díaz
“While current policies exert strong control on the import and export of living organisms, including pests, across countries, until only a few decades ago, very little attention was paid to this issue. This means that many species were translocated to new regions without any consideration of their potential impacts,” says Dr Javier Galán Díaz.
An example of this is the massive plant exchange among Mediterranean‐type regions as a consequence of European colonialism: crops and cattle were exported, along with tools and materials, potentially bringing along the seeds of many plant species.
Agricultural landscape dominated by exotic species of European origin (Merced Vernal Pool and Grassland Reserve, California, U.S.A.). Photo by Dr Javier Galán Díaz
“So far, most studies on plant invasions have tried to explain the success of exotic species by comparing their traits with those of the native plant communities where they arrive, or by comparing the traits of plant species that have achieved different levels of invasion in the same region. But, if we take into account that the most common plant species from European agricultural landscapes have been in contact with humans and have therefore had the potential to be inadvertently transported to other Mediterranean regions, then only those that have successfully invaded other regions have something different in them that allowed them to establish and spread abroad,” Dr Galán Díaz explains.
Following this approach, the scientists found that, when comparing plant species transported from the Mediterranean Basin to other Mediterranean-climate regions (California, Central Chile, the Cape Region of South Africa and Southwestern and South Australia) in the search of predictors of invasiveness, only those species with large distribution ranges that occupy climatically diverse habitats in their native region became exotic. Also, species with many dispersal vectors (for instance those that have seeds dispersed by animals, water or wind), long bloom periods and acquisitive above- and belowground strategies of resource use are most likely to become exotic. Most of this plant information is readily available or easy to obtain from free and open-access repositories.
Lotus corniculatus, one of the species that the study identified as invasive in other Mediterranean-climate regions of the world. Photo by Teresa Grau Ros under a CC-BY 2 license
Rumex acetosella, one of the species that the study identified as invasive in other Mediterranean-climate regions of the world. Photo by Jakub T. Jankiewicz under a CC-BY 2 license
Carduus tenuiflorus, one of the species that the study identified as invasive in other Mediterranean-climate regions of the world. Photo by jacinta lluch valero under a CC-BY 2 license
Poa pratensis, one of the species that the study identified as invasive in other Mediterranean-climate regions of the world. Photo by AnneTanne under a CC BY-NC-SA 2 license
“Determining the factors that pre-adapt plant species to successfully establish and spread outside of their native ranges constitutes a powerful approach with great potential for management,” the researchers write in their paper. “This framework has the potential to improve prediction models and management practices to prevent the harmful impacts from species in invaded communities.”
“Using the existing information, we can identify the key species to monitor. This is especially encouraging in the era of Big Data, where observations from citizen science applications add to those of scientists, increasing the potential of screening systems,” Dr Galán Díaz says in conclusion.
This happens more than you might think, with pet releases deemed responsible for 53% of invasive vertebrate species and one third of all aquatic invasive species. It has been shown that the more readily available a species is in the pet trade, the greater the risk of it being released, or escaping, into the wild.
Somewhat fascinatingly, this also puts the trade at the mercy of pop culture influences. 1970s animated series “Rascal the Raccoon” is commonly blamed for Japan’s invasive racoon population, and demand for Trachemys scripta pets is said to have boomed in the 1990s due to “Teenage Mutant Ninja Turtles.” Side note: the influence of movies highlighting the challenges of pet ownership, such as “Gremlins” or “Little Shop of Horrors”, warrants further study.
While invasion ecology has typically focused on these released species and the impacts that they cause, many species are sold with commensal organisms attached. These incidentally carried fauna are commonly known as “hitchhikers”.
Recent studies have found the protozoan Vorticella sp. and a species of bdelloid rotifer associated with two species of atyid shrimps, digenean larvae with the carnivorous snail Anentome helena, and an epibiont, Diceratocephala boschmai, on New Guinean ornamental Cherax crayfish.
Temnocephalid eggs located on thorax carapace (white arrow) of adult Cherax monticola. From Ložek F, Patoka J, Bláha M. 2021. Another hitchhiker exposed: Diceratocephala boschmai (Platyhelminthes: Temnocephalida) found associated with ornamental crayfish Cherax spp. Knowl. Manag. Aquat. Ecosyst., 422, 25.
A high-profile example emerged in 2021 when zebra mussels (Dreissena polymorpha) were detected in 21 US states on aquarium moss balls that had been imported from Ukraine, and subsequent searches revealed the species in 600 locations in Canada. Similar findings have since emerged from Europe. Having colonised both European and North American waters, the ease with which this Ponto-Caspian bivalve is being spread by the pet trade on both sides of the Atlantic is a major concern. Zebra mussels have been listed as one of the IUCN’s “100 of the Worst Invasive Species”, and their myriad ecological and economic impacts range from habitat alteration, to competition with native unionids, to disruption of food-web structure, to blocking industrial water intake pipes. They are also able to attach to boat hulls and other organisms, facilitating further spread.
Zebra mussels, Dreissena polymorpha, found amongst ordered European pond snail, Viviparus viviparus
I remember the moment clearly. I had ordered seventy-five Viviparus viviparus – a common European pond snail species – for behavioural studies at GEOMAR Helmholtz Centre for Ocean Research Kiel where I was based for lab work in the group of Elizabeta Briski. After some stress over posting delays and an increasingly fraught relationship developing with the GEOMAR receptionist, the snails arrived. Over the next day, watching them go about their lives in our climate chamber in their new tanks became a favourite way to spend working breaks. With obvious dimorphism you could clearly tell males from females, which added to the developing snail soap operas. However, just before packing up to leave the lab, I noticed a huge lump on one snail. What on earth is that? Soon I noticed a second. I called Elizabeta with my suspicions, which she confirmed the next day. Photos were taken, measurements made, and our go-to ecological geneticist Reid Brennan was begged to work his DNA sequencing magic. Before long, it was all confirmed: we had zebra mussels.
The biggest takeaway message here is that even native species in the pet trade can facilitate the spread of non-native hitchhikers. In a parallel universe, those snails did not go to an invasion ecology lab but rather to someone keen to stock their garden pond. Escape from ponds is a major pathway for freshwater species introductions, and even if the impact of a native species escaping might be limited, its potential for the zoochorous dispersal of a non-native should not be ignored.
Zebra mussels, Dreissena polymorpha, found amongst ordered European pond snail, Viviparus viviparus.
Of course, questions surround the conditions under which the pond snails were held before selling. Were they stocked in zebra mussel infested outdoor ponds? Which other species are held in a similar way? How prevalent are these practices within the trade? One way of combating this risk of non-native species spread is via legislation. Calls have been made for white lists of low-risk species that can be sold in the trade in place of risky species, but in our study, the issue stems from the selling of a native species within its native range, which would surely be deemed low-risk.
We propose that should a white-list system be adopted, the potential for a “low-risk” species to transport invasive species must be accounted for. We also call for stricter biosecurity practices to be enforced, including regular checking and disinfecting of outdoor stock ponds where appropriate. Tools such as environmental DNA surveillance could be used to effectively detect the presence of targeted invasive species, as part of biosecurity “audits”. However, for the time being, a desperate, final line of defence is to raise awareness amongst consumers and for them to be wary of unwanted hitchhikers.
Dickey JWE, Brennan RS, Chung SS, Jeschke JM, Steffen GT, Briski E (2023) More than we bargained for: Zebra mussels transported amongst European native freshwater snails. NeoBiota 10: 1–10. https://doi.org/10.3897/neobiota.83.97647
DeRoy EM, Scott R, Hussey NE, MacIsaac HJ (2020) Density dependence mediates the ecological impact of an invasive fish. Diversity and Distributions 26: 867–880. https://doi.org/10.1111/ddi.13063
Gippet JMW, Bertelsmeier C (2021) Invasiveness is linked to greater commercial success in the global pet trade. Proceedings of the National Academy of Science USA 118. https://doi.org/10.1073/pnas.2016337118
Lozek F, Patoka J, Bláha M (2021) Another hitchhiker exposed: Diceratocephala boschmai (Platyhelminthes: Temnocephalida) found associated with ornamental crayfish Cherax spp. Knowledge and Management of Aquatic Ecosystems 2020-Janua. https://doi.org/10.1051/kmae/2021023
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Patoka J, Patoková B (2021) Hitchhiking Exotic Clam: Dreissena polymorpha (Pallas, 1771) Transported via the Ornamental Plant Trade. Diversity 13: 1–5.
Patoka J, Magalhães ALB, Kouba A, Faulkes Z, Jerikho R, Vitule JRS (2018) Invasive aquatic pets: Failed policies increase risks of harmful invasions. Biodiversity and Conservation 27: 3037–3046. https://doi.org/10.1007/s10531-018-1581-3
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Zeng Y, Shakir KK, Yeo DCJ (2019) Competition between a native freshwater crab and an invasive crayfish in tropical Southeast Asia. Biological Invasions 21: 2653–2663. https://doi.org/10.1007/s10530-019-02009-6
While invasive alien species (IAS) represent a growing threat to global biodiversity and ecosystems, public awareness of them hasn’t seen a significant increase. Many researchers believe informing people about IAS is an essential long-term investment to counter biological invasions; in particular, “learning by doing” is an extremely effective method for involving new audiences, such as students.
Map of the study area (the Veneto Region) indicating the high school locations.
About 500 Italian students aged 11-18 took part in a citizen science project that led to new geographical records of two alien species of ambrosia beetles considered to be quarantine pests by the European Union. Dr. Fernanda Colombari and Prof. Andrea Battisti of the University of Padova have described the results in a paper in the open-access journal NeoBiota.
The project involved schools located in urban areas in north-eastern Italy and aimed to connect environmental education and experiential outdoor learning through lectures, videos, reports, and large-scale surveillance of ambrosia beetles. The students used plastic bottles and hand sanitizer to trap ambrosia beetles in their school grounds. They then assessed their abundance, looking at the different species. Before and after the educational activities, their knowledge and awareness of IAS were tested using simple anonymous questionnaires.
Schematic representation of a plastic bottle trap filled with hand sanitizer as attractant
“Our study aimed to both educate students and collect scientific data at sites such as schools where surveillance for potentially invasive ambrosia beetles is not usually conducted, or where it is sometimes misunderstood,” Dr. Colombari and Prof. Battisti write in their paper.
Identifying the specimens collected by the students, the authors found that IAS amounted to 35% of total catches. Remarkably, two out of the four alien species caught, Cnestus mutilatus and Anisandrus maiche, were recorded for the first time in Europe thanks to this study.
Furthermore, questionnaire results showed that the students acquired greater knowledge and increased their awareness and interest in IAS by more than 50%. After the experiment, most of them were interested in learning more about the negative effects of the introduction of IAS and practices to limit their spread.
This study shows that citizen science can successfully involve school students, giving them an opportunity to contribute in an effective early detection of IAS, as most first records occur in cities or suburban areas. The results also point to the primary role of education, which is as a major driver of change in tackling sustainability challenges. Moreover, as students bring home the message and share it with their relatives, the process supports intergenerational learning and enlarges public collaboration.
A plastic bottle trap filled with hand sanitizer as attractant. Photo by Dr Fernanda Colombari
“People are often unaware of the role they have in the entire invasive process,” the researchers write in their study. Citizen science projects like this one are more than a reliable tool for collecting scientific data; they also help engage the public and spread awareness of biological invasions, eventually contributing to the creation of more efficient management strategies.
The monitoring programme in this study was conducted in the context of the European project HOMED (Holistic management of emerging forest pests and diseases), which has developed a full panel of scientific knowledge and practical solutions for the management of emerging native and non-native pests and pathogens threatening European forests. The main results of HOMED’s research are publically available in a special issue in the open-access scholarly journal NeoBiota.
Colombari F, Battisti A (2023) Citizen science at school increases awareness of biological invasions and contributes to the detection of exotic ambrosia beetles. In: Jactel H, Orazio C, Robinet C, Douma JC, Santini A, Battisti A, Branco M, Seehausen L, Kenis M (Eds) Conceptual and technical innovations to better manage invasions of alien pests and pathogens in forests. NeoBiota 84: 211-229. https://doi.org/10.3897/neobiota.84.95177
Every year, new alien species of insects and fungi invade European forests. Some of them are exotic pests and diseases that can affect the survival and growth of trees.
To help develop strategies for monitoring and managing these non-native forest pests, a consortium of over 50 scientists representing 23 research institutions and 15 countries from across the globe joined their skills in the Horizon 2020 project HOMED “Holistic management of emerging forest pests and diseases.”
Alex Stemmelen during his presentation at the XXVI ICE Congress 2022. He is the first author of a paper on the pests of Douglas fir in NeoBiota‘s special issue.
Between 2018 and 2022, the HOMED consortium developed a full panel of scientific knowledge and practical solutions to better deal with emerging native and alien invasive pests and diseases.
Fruiting bodies of Austropuccinia psidii on Myrtus communis (symptoms of myrtle rust). Photo by Alberto Santini
This includes targeting the successive phases of invasion, and developing innovative methods for each phase: risk analysis, prevention/detection, surveillance, eradication/containment, and control.
To share the results of this cooperation and help researchers further improve the management of emerging forest pests and pathogens, HOMED has made the main outcomes of its research publically available.
They are now published in a special issue in the open-access journal NeoBiota, called “Conceptual and technical innovations to better manage invasions of alien pests and pathogens in forests”. The issue comprises 16 articles on various aspects of the ecology and management of invasive alien insects and fungal pathogens in Europe’s forests.
“Because forests provide irreplaceable goods and materials for people and the European economy, because maintaining healthy forests is essential for their contribution to climate change mitigation through sequestration and storage of atmospheric carbon, it is urgent to develop more effective protective measures against the ever-increasing threat of invasive forest pests,” the editors of the special issue write in an editorial.
More tools are needed that can help identify, prevent and monitor invasive alien species and improve early warning methods, which makes the research in this issue so crucial and timely.
The European project Homed, leaded by Hervé Jactel, gave the opportunity to produce a lot of important scientific results, these are just a part! Incredibly happy and proud!https://t.co/VeIK5zvC7I
“The role of researchers is to develop, test and promote the most relevant methods and tools at each stage of the invasion framework, i.e., for the early detection of these invasive alien organisms, for the identification of the species and for the monitoring of their damage and spread, but also for new eradication and control solutions,” the editors continue.
Hervé Jactel, Lukas Seehausen and Martin Gossner at HOMED’s and Pensoft’s stand during the XXVI ICE Congress 2022.
One highlight in the published research is a study exploring how using the methods of citizen science at schools can increase invasive species awareness. Another explores the efficiency of artificial intelligence in pest detection.
“The publications collected in this special issue demonstrate that current conceptual, methodological, and technological advances allow a great progress in the anticipation, monitoring and management of invasive pest species in forests,” the editors conclude.
The U.S. Geological Survey has released a comprehensive synthesis of Burmese python science, showcasing results from decades of USGS-funded research on python biology and potential control tools. The giant constrictor now represents one of the most challenging invasive species management issues worldwide.
Occurrence records were obtained from a large geospatial database of invasive species reports (Early Detection & Distribution Mapping System) submitted by both researchers and the public. The map illustrates the chronology of python removals across southern Florida and represents the best professional estimate of the invasion front, which is not exact and will change over time.
“For the first time, all the science on python ecology and potential control tools has been consolidated into one document, allowing us to identify knowledge gaps and important research areas to help inform future python management strategies. This synthesis is a major milestone for Burmese python research; six years in the making, it represents the consensus of the scientific community on the python invasion,” said USGS Ecologist Jacquelyn Guzy, lead author for the publication.
Burmese pythons were confirmed to have an established breeding population in Everglades National Park in 2000. The population has since expanded and now occupies much of southern Florida. They consume a wide range of animals and have altered the food web and ecosystems across the Greater Everglades.
Photo by U.S. Geological Survey.Photo by Conservancy of Southwest Florida.Photo by U.S. Geological Survey.Burmese pythons.
The synthesis, which pulled together the expertise of scientists and managers nationwide, provides a breakdown of 76 prey species found in python digestive tracts, which primarily included mammals and birds, as well as two reptile species, American alligator and Green iguana. However, as the scientists noted, the number of animals may increase as the python population expands to new areas.
It also reports new findings including a summary of body sizes of pythons measured by state and federal agencies between 1995 and 2022, as well as descriptions of length-mass relationships, the estimated geographic spread of pythons over time, and a comprehensive assessment of all control tools explored to date.
Illustration by Natalie Claunch demonstrates typical features of the Burmese python.
One of the hallmark issues of the Burmese python invasion has been the difficulty of visually detecting or trapping pythons in an immense natural landscape, Guzy said. Pythons do not readily enter any type of trap, occupy vast stretches of inaccessible habitat, and camouflage extremely well within the subtropical Florida environment.
Examples of cryptic coloration contributing to low detection probability in representative habitat where Burmese pythons have been captured. White circles indicate pythons. Photos by
“Extremely low individual python detection rates hamper our ability to both estimate python abundance and expand control tools across the extensive natural landscape” says USGS Research Ecologist Kristen Hart, an author of the publication.
Because the Burmese python has spread throughout southern Florida, eradication of the population across the landscape is not possible with existing tools, the publication states. However, researchers at USGS and partner institutions are exploring potential novel techniques such as genetic biocontrol, that may one day provide an avenue towards larger-scale population suppression.
Eradication of the population across the landscape is not possible with existing tools, a new report states. USGS and partners are "exploring potential novel techniques such as genetic biocontrol, that may one day provide an avenue towards larger-scale population suppression."
In the meantime, important areas of research according to the publication include reproductive life history and estimation of demographic vital rates such as survival, to help managers evaluate and refine existing control tools. With improved control tools managers may be able to reduce population expansion and minimize the future impact of pythons on the environment.
The USGS python research over the past decades has been largely supported by the USGS Greater Everglades Priority Ecosystem Sciences (GEPES) Program with additional support from the USGS Biothreats and Invasive Species program.
Guzy JC, Falk BG, Smith BJ, Willson JD, Reed RN, Aumen NG, Avery ML, Bartoszek IA, Campbell E, Cherkiss MS, Claunch NM, Currylow AF, Dean T, Dixon J, Engeman R, Funck S, Gibble R, Hengstebeck KC, Humphrey JS, Hunter ME, Josimovich JM, Ketterlin J, Kirkland M, Mazzotti FJ, McCleery R, Miller MA, McCollister M, Parker MR, Pittman SE, Rochford M, Romagosa C, Roybal A, Snow RW, Spencer MM, Waddle JH, Yackel Adams AA, Hart KM (2023) Burmese pythons in Florida: A synthesis of biology, impacts, and management tools. NeoBiota 80: 1-119. https://doi.org/10.3897/neobiota.80.90439
Story originally published by the USGS. Republished with permission.
The scientists examined a total of nearly 200 animals living in the wild in lakes in Freiburg and Kehl. Their findings suggest that the turtles have established themselves in a new habitat, where they could become a threat to the local ecosystem.
For two species, this is the first evidence of independent reproduction outside of their natural reproductive range. For the third species, this is the northernmost evidence of its presence up to now,
The false map turtle (Graptemys pseudogeographica) enjoys the sun’s warmth. Photo: Johannes Penner.
Turtles released into the wild
Invasive species do a great deal of economic damage world-wide. They also contribute to advancing global species extinctions.
Alien reptiles regularly make their way into the wild in Germany. Most often, this is because they have been released by pet owners.
Large numbers of North American pond sliders (Trachemys scripta) were imported into the European Union (EU) in the 1980s and 1990s as house pets. In 1997, their import into the EU was banned. By 2016, the sale of specimens born here was also made illegal. Since then, pet shops have replaced them with other freshwater turtles, such as the river cooter (Pseudemys concinna) and the false map turtle (Graptemys pseudogeographica).
Genetic analyses of specimens of all three species in a range of ages have now demonstrated that they are reproducing independently in local waters.
What’s surprising is that the invasive species have established themselves so far north. In Europe, successful reproduction and self-maintaining populations of Trachemys scripta were only known in the Mediterranean regions and the continental climate zone of Slovenia,
explains Benno Tietz.
Until recently, it had been assumed the turtles being examined couldn’t reproduce in Central Europe due to the colder climate. Especially the false map turtle is actually quite sensitive to the cold,
A North American pond slider (Trachemys scripta) resting on a lily pad. Photo: Johannes Penner.
Consequences for local species unclear
The invasive turtles could become a problem for indigenous species.
The European pond turtle (Emys orbicularis), for example, is now only present in Germany in parts of Brandenburg.
In an experimental setup, the European pond turtle showed weight loss and an increased death rate when being kept together with Trachemys scripta,
Penner says that could be caused by the larger, alien species forcing the smaller local turtles from places where they sun themselves, leading the local turtles to have problems with thermoregulation. Or perhaps the competition led to them having greater challenges when seeking food.
Beyond that, aquatic turtles could be hosts for viruses and parasites, leading them to play a role in the spread of diseases. This could potentially have a damaging influence on other parts of the ecosystem, including amphibians, fish, or aquatic plants.
On the other hand, in their study, the researchers consider the alien species could assume functions in damaged ecosystems that would otherwise go unreplaced.
Vamberger says these questions urgently need to be explored further.
We need to raise public awareness that people should not release – no matter what kind of species – any animals into the wild in future.”
A river cooter (Pseudemys concinna) lets itself drift in the water. Photo: Johannes Penner.
Benno Tietz has completed a Master’s degree in Environmental Sciences at the University of Freiburg. His thesis – finished in the Winter Semester of 2020/2021 – investigated alien turtles. Currently, he is a research assistant at the Freiburg Institute of Applied Animal Ecology.
Tietz B, Penner J, Vamberger M (2023) Chelonian challenge: three alien species from North America are moving their reproductive boundaries in Central Europe. NeoBiota 82: 1-21. https://doi.org/10.3897/neobiota.82.87264