Tag: invasive species

Can we predict if a plant species will become exotic?

A new approach compared characteristics of species that succeeded or failed to establish after probably following the same historical introduction route.

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.

Dr Javier Galán Díaz, University of Seville, Spain, Dr Enrique G. de la Riva, University of León, Spain, Dr Irene Martín-Forés, The University of Adelaide, Australia, and Dr Montserrat Vilà, Doñana Biological Station (EBD-CSIC), Spain, described their findings in a new paper in the open-access journal NeoBiota.

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.

Research article:

Galán Díaz J, de la Riva EG, Martín-Forés I, Vilà M (2023) Which features at home make a plant prone to become invasive? NeoBiota 86: 1-20. https://doi.org/10.3897/neobiota.86.104039

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When life gives you zebra mussels

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.

Guest blog post by James Dickey

The role played by the global pet trade in the spread of invasive alien species is increasingly gaining attention. Media outlets have excitedly picked up on stories of released goldfish growing to the size of rugby balls, Amazonian catfish appearing in Scottish rivers, and North American crayfish terrorising Tiergarten tourists in Berlin. In recent years I’ve been drawn to these stories, despite the simplistic, repetitive plot: well-meaning but feckless owners can no longer give pets the care they deserve, they struggle to rehome the pets, they release the pets into the wild, chaos ensues.

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.

Hitchhikers

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.

The discovery

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.

Potential implications

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.

References:

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

Militz TA, Foale S (2017) The “Nemo Effect”: Perception and reality of Finding Nemo’s impact on marine aquarium fisheries. Fish and Fisheries 18: 596–606. https://doi.org/10.1111/faf.12202

Padilla DK, Williams SL (2004) Beyond ballast water: Aquarium and ornamental trades as sources of invasive species in aquatic ecosystems. Frontiers in Ecology and the Environment 2: 131–138. https://doi.org/10.1890/1540-9295(2004)002[0131:BBWAAO]2.0.CO;2

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

Richardson MJ, Whoriskey FG, Roy LH (1995) Turbidity generation and biological impacts of an exotic fish Carassius auratus, introduced into shallow seasonally anoxic ponds. Journal of Fish Biology: 576–585.

Saul WC, Roy HE, Booy O, Carnevali L, Chen HJ, Genovesi P, Harrower CA, Hulme PE, Pagad S, Pergl J, Jeschke JM (2017) Assessing patterns in introduction pathways of alien species by linking major invasion data bases. Journal of Applied Ecology 54: 657–669. https://doi.org/10.1111/1365-2664.12819

Simberloff D (2006) Risk assessments, blacklists, and white lists for introduced species: Are predictions good enough to be useful? Agricultural and Resource Economics Review 35: 1–10. https://doi.org/10.1017/S1068280500010005

Stanicka A, Maciaszek R, Cichy A, Templin J, Świderek W, Żbikowska E, Labecka AM (2022) Unwanted ‘hitchhikers’ of ornamental snails: A case report of digeneans transported via the international pet trade. The European Zoological Journal 89: 601–607. https://doi.org/10.1080/24750263.2022.2065039

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

Beetles in a bottle: a message from aliens to schools

A citizen science project in Italy had high school students monitor the activities of ambrosia beetles, catching them with traps made from recycled plastic bottles.

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.

Cnestus mutilatus. Photo by Durham Field Office – Forest Health Protection under a CC BY-NC-SA 2.0 license.

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.

Original source:

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

New NeoBiota special issue: tackling invasive alien forest pests in Europe

The issue comprises 16 articles on various aspects of the ecology and management of invasive alien insects and fungal pathogens in Europe’s forests.

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.

The cover of NeoBiota’s new special issue.

“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 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.

Follow HOMED on Twitter. Follow NeoBiota on Twitter and Facebook. See the latest tweets on the special issue using the hashtag #HOMED_SI.

Comprehensive review of Burmese python science released

A USGS-led publication offers a new look at the constrictor that has invaded southern Florida.

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.

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.

Research article:

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.

North American turtles establish succcessful populations in Germany, possibly threathening ecosystems

For the first time, self-sustaining populations of three non-native species of turtles were identified in south-western Germany by researchers at the University of Freiburg

For the first time, self-sustaining populations of three non-native species of turtles were identified in south-western Germany by researchers at the University of Freiburg

Original text published by the University of Freiburg

Three species of turtles native to North America have been successfully reproducing in the wild in Germany, report for the first time environmental researcher Benno Tietz and biologist Dr. Johannes Penner of the University of Freiburg, along with Dr. Melita Vamberger of the Senckenberg Natural History Collection in Dresden.

Their results were published in the open-access scientific journal NeoBiota.

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,

says Penner.
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,

he says.
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,

reports Penner.

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.”

she insists.
A river cooter (Pseudemys concinna) lets itself drift in the water. Photo: Johannes Penner.
Meet the research team:

Dr. Johannes Penner was the scientific coordinator of the research training group “Conservation of Forest Biodiversity in Multiple-Use Landscapes of Central Europe” (ConFoBi) and a lecturer for the Chair of Wildlife Ecology and Management of the University of Freiburg. Currently, he is a curator at the NGO “Frogs and Friends” and a guest researcher in wild animal ecology.

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.

Dr. Melita Vamberger is a researcher at the Senckenberg Natural History Collection in Dresden.

***

The study was supported by the Hans Schimenz Fund of the German Society for Herpetology and Terrarium Science (DGHT) as well as the Academic Society of Freiburg.

***

Research paper:

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

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Where did all those insects come from? Tracking the history of insect invasion in Chile

Going through centuries-old literature, researchers compiled a database of the exotic insects established in the country.

Guest blog post by Daniela N. López, Eduardo Fuentes-Contreras, Cecilia Ruiz, Sandra Ide, Sergio A. Estay

Understanding the history of non-native species arrivals to a country can shed light on the origins, pathways of introduction, and the current and future impacts of these species in a new territory. In this sense, collecting this information is important, and sometimes essential, for researchers and decision makers. However, in most cases, reconstructing this history takes a lot of work. Finding antique references is hard work. To add more complexities, changes in the taxonomy of species or groups could be frustrating as we try to track the moment when a species was referenced in the country for the first time, sometimes centuries ago. Of course, we only learned about these issues when, almost seven years ago, we thought that compiling a database for the exotic insects established in Chile would be interesting to people working on invasive species in the country.

Tremex fuscicornis caught in Chile. Photo by Sergio Estay

First, we collected information from physical and electronic books and journals available in our institutional libraries, but soon we noticed that we needed a more significant effort. In Chile, the National Library and The National Congress library allowed us to review and collect information from texts, in many cases, over a hundred years old. We also had to request information from foreign specialized libraries and bookstores. Sometimes, we had to negotiate with private collectors to buy antique books or documents. When we figured the first version of the database was ready, we began a second step for detecting errors, correcting the taxonomy, and completing the information about the reported species.

Ctenarytaina eucalypti individuals and damage in Chile. Photo by Sergio Estay

The analysis began when we finally completed the database. What types of questions could we answer using this data? Was the database complete enough to detect historical, biogeographic, and ecological patterns? Two competing hypotheses were the starting point for the study at this stage. On the one hand, the species that dominated the non-native insect assemblage could have come from original environmental conditions that matched Chile’s. Or, the pool of non-native insects arrived using pathways associated with the country’s economic activities, regardless of their origin.

We found records of almost 600 non-native insect species established in continental Chile. Most species corresponded to Hemiptera (true bugs and scales, among others) from Palaearctic origin and were linked to agriculture and forestry, as we initially hypothesized. These characteristics point to the central role of intercontinental human-mediated transport in structuring non-native insect assemblages in Chile. Non-native insect introductions began immediately after the arrival of Europeans to the central valley of Chile and have shown an enormous acceleration since 1950. Using data on the economic history of Chile, we can preliminary link this acceleration with the strong development in agriculture and forestry in Chile after World War II and the increase in intercontinental air traffic.

Exotic aphids in garden in Chile. Photo by Sergio Estay

The development and analysis of this database gave us some preliminary answers about the ecology of invasive insect species and opened the door to new questions. Also, this is a work in progress. We need the scientific community’s support to improve and correct the records, provide new reports and collect further references to support the database. Our data and analysis may be representative of other countries in South America. Similarities between our countries can facilitate using this information to manage recent introductions and prevent significant economic, social, or environmental damage.

Reference

López DN, Fuentes-Contreras E, Ruiz C, Ide S, Estay SA (2023) A bug’s tale: revealing the history, biogeography and ecological patterns of 500 years of insect invasions. NeoBiota 81: 183-197. https://doi.org/10.3897/neobiota.81.87362

Tracking an invasion – a single Asian hornet sparked the ongoing spread across Europe

It is likely that all Asian hornets in Europe are descended from a single queen introduced to France in 2004.

In Europe, the Asian (or “Yellow-legged”) Hornet (Vespa velutina) is a predator of insects such as honeybees, hoverflies, and other wasps, and poses serious risks to apiculture, biodiversity and pollination services. This hornet can measure up to 4cm in length and, like all other social wasps, is capable of delivering a painful sting, although it is not aggressive by nature. Thought to have been introduced into Europe from China in 2004, the Asian Hornet has rapidly spread across the continent. While it has been thus far controlled in Britain, the hornet is well established across mainland Europe and the Channel Islands. In April 2021, the Irish National Parks and Wildlife Service confirmed that a single specimen had been found, ‘alive but dying’ in a private dwelling in Dublin, marking the first Irish record of this species.  

The Asian Hornet specimen recovered in Dublin. Image by Dr Aidan O’Hanlon

The circumstances of how the specimen arrived in the Irish capital are not known, but with the area’s extensive regional, national and international connectivity, there can be many possible pathways of introduction. In an Irish context, it was of particular interest to determine whether this individual originated in Europe/Britain or represented a potential new invasion source from within its native range in Southeast Asia.

The specimen was deposited in the National Museum of Ireland and identified by Dr. Aidan O’Hanlon, who suggested performing genetic analysis to determine its provenance. In collaboration with scientists from the School of Biological, Earth and Environmental Sciences (BEES), University College Cork, and partners on the EU Atlantic Positive Project (which aims to establish Europe-wide methodologies for the control of the Asian hornet), genetic analysis was performed and data were compared with those from specimens provided from several other locations across Europe. The researchers then published their findings in Journal of Hymenoptera Research.

An Irish hornet. Image by Danel Solabarrieta, licensed under CC BY-SA 2.0.

“Earlier work had demonstrated that Asian hornets in Europe apparently shared the same genetic lineage, based on studies of a single gene. We took this a step further and looked at two additional genes which would be more sensitive in detecting variation within the invasive population”, explains Dr. Eileen Dillane of BEES.

Data from all three genetic markers confirmed that not only are Asian hornets in Europe of a single pedigree, but are likely descended from a single mated queen hornet that somehow arrived in France in 2004.  Furthermore, this lineage has not yet been described within the native range. 

“Our research has revealed the remarkable potential for population expansion of eusocial insects in invaded areas, even when original genetic diversity is extremely low”, says Dr. Simon Harrison, who is part of the research team .

Female V. velutina specimen from Dublin, Ireland.

These findings are both bad news and good news for the control of the Asian hornet in Europe. Whilst single mated queens can evidently rapidly re-colonise areas from where hornets have been eradicated (for example, where intensive efforts have destroyed all nests in an area), the close relatedness of all individuals of the Asian hornet in Europe offers hope for eradication methods based on biological control. 

In the Irish context, it is unlikely that this is the beginning of a larger-scale invasion, as the climate and habitat landscape of Ireland is likely less than ideal for the Asian hornet, which requires higher summer temperatures and a greater supply of energy-rich food. “Nonetheless, climate change is likely to increase the threat of a successful invasion in the future, so vigilance against this species must be maintained”, the authors of the study advise.

Original source:

Dillane E, Hayden R, O’Hanlon A, Butler F, Harrison S (2022) The first recorded occurrence of the Asian hornet (Vespa velutina) in Ireland, genetic evidence for a continued single invasion across Europe. Journal of Hymenoptera Research 93: 131-138. https://doi.org/10.3897/jhr.93.91209

Invasive fruit fly may pose threat to forest ecosystems

The decay of fruits attacked by the spotted wing drosophila leads to a loss of resources, which can cause considerable ecological damage.

The invasive spotted wing drosophila (SWD), introduced from South-East Asia, is a well-known fruit crop pest. It lays its eggs by destroying the mechanical protection of the fruit’s skin, providing an entry point for further infestation. Egg deposition and inoculated microbes then accelerate decay, and as a result the fruit rots and becomes inedible. While this small fly is known to cause massive economic damage in agriculture, little is known about its ecological impact on more natural ecosystems such as forests.

The larvae of the invasive spotted wing drosophila develops in fruits of many forest species such as brambles. Its occurrence result in a fast decay of the fruits.

A recent study by Swiss scientists from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL and the Ökobüro Biotopia, published in the scientific journal NeoBiota, concluded that the SWD competes strongly with other fruit-eating species and that its presence could have far-reaching consequences for ecosystems.

The research team assessed the use of potential host plants at 64 sites in forests from mid-June to mid-October 2020 by checking a total of 12,000 fruits for SWD egg deposits. To determine if SWD attacks trigger fruit decay, they also recorded symptoms of fruit decay after egg deposition. In addition, they monitored the fruit fly (drosophilid) fauna in the area, assuming that the SWD would outnumber and possibly outcompete other fruit-eating insects.

The male of the invasive spotted wing drosophila can be easily identified by the dark spots on the wings.

The authors found egg deposits on the fruits of 31 of the 39 fruit-bearing forest plant species they studied, with 18 species showing an attack rate of more than 50%. Furthermore, more than 50% of the affected plant species showed severe symptoms of decay after egg deposition. The egg depositions may alter the attractiveness of fruits, because they change their chemical composition and visual cues, such as colour, shape and reflective patterns, which in turn might lead seed dispersers such as birds to consume less fruits.

Given the large number of infested fruits, significant ecological impacts can be expected. “Rapid decay of fruits attacked by the spotted wing drosophila results in a loss of fruit available for other species competing for this resource, and may disrupt seed-dispersal mutualisms due to reduced consumption of fruit by dispersers such as birds,” says Prof. Martin M. Gossner, entomologist at the WSL. “If the fly reproduces in large numbers, both seed dispersers and plants could suffer.”

The females of the invasive spotted wing drosophila has an enlarged, serrated ovipositor to attack undamaged fruits, which gives it a competitive advantage over native fruit flies.

The authors further found that SWD were strongly represented and dominant in trap catches, and showed that the more abundant SWD were, the less abundant native drosophilids were. This suggests additional negative impacts of the invasive species on native communities.

With ongoing climate change, these potentially severe ecological impacts might be amplified in temperate forests, as higher average and winter temperatures will most likely lead to shorter generation times and lower winter mortality, which will eventually further increase the pressure on forest fruits and the competitiveness of the SWD over native drosophilids, the authors note.

Research article:
Bühlmann I, Gossner MM (2022) Invasive Drosophila suzukii outnumbers native controphics and causes substantial damage to fruits of forest plants. NeoBiota 77: 39-77. https://doi.org/10.3897/neobiota.77.87319

Photos by Prof. Martin M. Gossner.

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Dr Giovanni Vimercati gave the Best Talk at NEOBIOTA 2022

The invasion scientist and NEOBIOTA 2022 awardee shares more about his research on the impact assessment of biological invasions.

Giovanni Vimercati is a postdoctoral researcher at the University of Fribourg, Switzerland, and most recently recipient of the Best Talk award (Early Career Researcher) at the 2022 NEOBIOTA conference held in mid-September in Tartu, Estonia. 

As a sponsor of the event and publisher of the NeoBiota journal, Pensoft granted a complimentary publication in it to the awardee. 

NeoBiota readers might already be familiar with Vimercati, whose name first appeared on its pages in a 2017 paper that used alien amphibians as a case study to identify the differences and potential difficulties with two impact assessment scoring tools: the Environmental Impact Classification of Alien Taxa (EICAT) and the Generic Impact Scoring System (GISS). 

Then, in 2020 and 2021, the researcher had two research articles published in NeoBiota as lead author. The 2020 paper provided a summary of the frameworks assessing beneficial impacts of alien species, while in the 2021 study his team used a spatially-explicit stage-structured model to assess efficacy of past, present and alternative control strategies for invasive guttural toads (Sclerophrys gutturalis) in Cape Town.

Giovanni Vimercati being awarded at NEOBIOTA 2022. Photo by Ana Novoa.

In anticipation of Vimercati claiming the Best Talk award with a forthcoming submission to the journal, we asked him to join us for an interview and share his thoughts on his research.  

Going back to the beginning, what sparked your interest in the study of invasive species in particular? What are the unique aspects of your research?

Like the episodic nature of many biological invasions, my first contact with the study of alien species was quite “unexpected”. Having a strong interest in herpetology, I had the luck to pursue my doctoral research at the Center of Excellence for Invasion Biology (CIB) in Stellenbosch, South Africa, where I studied the invasion of an alien amphibian species. My PhD study, and the highly stimulating community of researchers that characterized the CIB, made me realize not only that invasive species provide an invaluable opportunity to address ecological and evolutionary questions, but also how important it is to study their impact on biodiversity and human communities. 

One unique aspect of my research since then has been its multidisciplinary character, as I have studied biological invasions from multiple angles simultaneously, by using mathematical models, physiological experiments, field surveys, remote sensing, literature reviews, meta analysis, and questionnaires. It seems a paradox, but the uniqueness of my research on biological invasions is that it has never really been unique! 

Are there recent developments in the field that you find particularly interesting to explore?

As many other scientific disciplines, the field of invasion science is highly dynamic, and novel developments emerge every year. However, I find of particular interest the development of new approaches and tools to explore the links between biological invasions and the various socio-economic contexts. The use of online structured and semi-structured interviews, or the development of standardized socio-economic indicators are, for example, particularly promising for future studies. 

In addition, the emergence of novel technological tools, for instance, linked to remote sensing, eDNA, stable isotopes and camera trapping, or the rapid increase in the computational power of modern CPUs, are allowing invasion scientists to collect and analyze data that used to be unaffordable, or simply unavailable. It is certainly an exciting moment to be an invasion scientist. 

What do you find to be the biggest challenges as a researcher in your field?

I find that the proliferation of hypotheses and frameworks that characterize the field of invasion biology are particularly intriguing and challenging. Many of them work extremely well in certain conditions or across specific taxonomic groups, but they often lack generality or are marred by context dependence, which may limit their predictive power. 

Addressing such a context dependence and finding ways to integrate various hypotheses and frameworks in invasion biology will be highly beneficial for understanding and forecasting biological invasions in the next decades. 

Another challenge is to communicate the implications of our research to non-experts. I often wonder how stakeholders and policymakers from different cultural backgrounds or geographic regions perceive alien species and their impacts.  

The theme of this year’s NEOBIOTA conference was “Biological Invasions in a Changing World”. To what extent can changes be anticipated and forecasted in order to make the work of assessing their impacts and mitigating damage easier?

I think that a key point would be to focus on specific indicators or proxies to measure these changes, so that different impacts and species can be quantified, both transparently and consistently. 

In recent years, the field has produced a huge body of literature regarding impacts caused by alien species, but the results of these studies have not always been comparable. I feel that the development of the EICAT framework and its recent adoption by the IUCN as a global standard for measuring the magnitude of environmental impacts of alien species were two very important steps in this direction. 

Your talk at the NEOBIOTA conference focused on the positive socio-economic impacts of invasive species. Why is this important for different stakeholders, including policy makers, but also local communities and individuals?

In my opinion, invasive species, and more generally alien species, can have various positive socio-economic impacts that should be identified and assessed rigorously. These impacts are often anecdotally reported or vaguely stated in the literature, a tendency that hampers our capacity to identify (and forecast) conflicts of interest among different stakeholders or understand their perceptions toward alien species. 

In my talk, I presented the preliminary version of a framework that assesses positive socio-economic impacts. The framework is based on the capability approach, and aims to quantify the degree to which the well-being of certain human communities increases after the introduction of alien species. Of course, the scheme won’t be used in isolation, but rather in combination with other frameworks that assess the negative socio-economic and environmental impacts of alien species, so that their effects can be understood in their full complexity.

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