Tag: invasive species

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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Assessments of alien species impacts are reliable to prioritize resources

Experts are consistent when assessing the economic, health and ecological impacts of alien species, find the scientists.

Original post by EBD-CSIC

An international collaboration led by the Doñana Biological Station (EBD-CSIC) has shown that experts are consistent when assessing the economic, health and ecological impacts of alien species. These assessments are therefore reliable to guide the prioritization of resources invested against biological invasions.

You can find the scientific article published in the open-access, peer-reviewed scholarly journal NeoBiota.

These results have a great impact on the management by national and international institutions, which have limited resources to fight against the growing and worrying increase of alien species invasions and the damage they caused to society and environment. 

Biological invasions annually cause huge food losses, disease transmissions, species extinctions and ecosystem perturbations. For these reasons, it is one of the biggest problems that humankind currently faces, and its relevance will alarmingly increase due to the extreme situations that climate change will expose society to.

The seriousness of this problem lies in the limited human resources available to fight against it, that force to prioritize its management. Here is where tools such as impact assessments play a key role. Assessments report the impact of invasive species in different areas, including economy, health and environment, and allow us to rank the most harmful species.

For instance, in aquatic ecosystems like the Ebro Delta in Spain, there are dozens of invasive alien co-occurring species that cause millions of economic losses and irreparable ecological damage.

Such is the case of the Zebra mussel, which affects irrigation; the apple snail that devours rice fields; and the blue crab causing the local extinction and declines of many native species.

“That’s why it is crucial to ensure that the results are not dependent on the assessors and to understand what factors affect discrepancies among experts,”

explains Rubén Bernardo-Madrid, lead author and researcher at Doñana Biological Station – CSIC.

One of the relevant aspects of this study is the quantification of the consistency of responses across assessors for a large number of invasive species of vertebrates, invertebrates and plants. In addition, the researchers have studied multiple protocols focused on different aspects, providing a global view of this problem.

“The study has shown that the great majority of assessments are consistent and therefore valid to aid in decision-making. These results are encouraging as they suggest that these protocols may be useful when facing the worrying forecasts of increasing biological invasions and their damages,” 

explains Rubén.

On the other hand, the researchers have observed that discrepancies across assessments might be due to multiple factors, such as the type of impact asked or the linguistic formulation used in the protocols.

The results suggest that there is room for improvement in assessments, but it will require more funding for research, and more multidisciplinary collaborations between ecologists and linguists to develop less ambiguous protocols.

As always, the most effective measure against biological invasions turns out to be prevention.

However, given the incapacity to control every voluntary and involuntary introduction, other tools such as impact assessments are essential to reduce as far as possible the damage caused by these species on human welfare and environment. Its continuous improvement and evaluation, such as the one made in this study, are decisive.

***

Research article:

Bernardo-Madrid R, González-Moreno P, Gallardo B, Bacher S, Vilà M (2022) Consistency in impact assessments of invasive species is generally high and depends on protocols and impact types. In: Giannetto D, Piria M, Tarkan AS, Zięba G (Eds) Recent advancements in the risk screening of freshwater and terrestrial non-native species. NeoBiota 76: 163-190. https://doi.org/10.3897/neobiota.76.83028

***

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Invasive species denialism: what is it, and what can we do about it?

Even when there is agreement on the impacts of invasive species on ecosystems, some stakeholders nevertheless deny the need for, or benefit of managing invasive species.

Guest blog post by Noelle G. Stratton, Nicholas E. Mandrak, and Nicole Klenk

Invasive species denialism (ISD) is a hot topic in recent invasion ecology discourse. Many of us are familiar with the concept of science denialism, particularly during recent discussions about climate change and the ongoing COVID-19 pandemic. Essentially, a person who exhibits science denialism is skeptical of, or refuses to believe, the scientific facts about a topic. Much of the discussion about ISD has focused on characterising it as a form of science denialism. However, while science denialism may be one form of ISD, it is not the only one.

Understanding the different forms of ISD is an important step in learning more about what drives ISD positions, and how those positions can be overcome to improve invasive species management. Recently, researchers at the University of Toronto outlined these ISD forms in a new paper in NeoBiota. While these framings are not the only ways to characterize invasive species denialism, they demonstrate that there are multiple framings to the ways that people deny the imperative to manage all invasive species as prescribed by early detection and rapid response.

So, what are the forms of ISD?

Venn diagram of the three forms of invasive species based on interviews and focus groups with invasive species community members in the Great Lakes region, including interested publics and decision-makers: 1) Invasive species denialism; 2) invasive species cynicism; and 3) invasive species nihilism. Each has different motivations and ways of talking about invasive species. Notably, all forms include an opposition to invasive species engagement or management efforts.

Invasive species denialism is the form that will typically come to mind when you picture a “science denialist”. Someone who does not believe in invasive species, or says that the existing scientific literature is all wrong, would fall within this framing. However, it is more complex than that. Invasive species practitioners also identified some of those who believed in invasive species and supported their management under this framing.

For example, folks who wanted management to happen immediately, be 100% effective, or have no risks to them or the environment whatsoever, were considered another form of denialist. This is because while these people supported invasive species management, they were still opposed to certain management efforts due to a lack of understanding of the science behind that management. Similarly, people who agree invasive species are a problem but say “this isn’t my problem, and I shouldn’t have to do anything about it” when shown evidence otherwise were also framed as denialists, as it again indicated a denial, or at least a lack of understanding of the scientific facts.

Invasive species cynicism is the form where someone may well understand what invasive species are and the science behind their management. However, they may still oppose management because they believe it will harm them in some way.

For example, someone who does not want to have to check and clean their boat to prevent an invasive species spread because it takes too much time would be categorized as an invasive species cynic. As well, someone who does not want to cooperate with management efforts because they personally like a particular invasive species and would like it to persist, despite knowing its potential for harms to the ecosystem or economy, is also an invasive species cynic. From these examples, it should be clear that this form of ISD is quite different from what we would think of as a “science denialist”. They understand the science, but it just does not motivate their beliefs or behaviour on this topic.

This research was also recently presented at the International Conference on Aquatic Invasive Species by co-author Noelle G. Stratton. Invasive species nihilism, in particular, prompted discussion both in-person and on social media.

Invasive species nihilism is the form that does not appear to take into account the science behind invasive species or their management at all. Rather, it revolves around the idea that invasive species research, management, or engagement are essentially a waste of time. The efforts were pointless and the results useless. This framing also differed from the other two forms in that the folks who expressed these beliefs often directly approached invasive species practitioners during the course of their work to inform them that their job was meaningless and to ask them why they bothered. This type of framing has the greatest potential to impact invasive species researchers and practitioners personally, and it is potentially the most difficult form of denialism to surmount during engagement and management efforts.

How can invasive species denialism impact management efforts?

ISD has the potential to hinder management efforts in a few different ways. Invasive species denialists may slow down decision-making by stalling or halting discussions with other stakeholders. In some cases, invasive species cynics have taken direct action to interfere with the implementation of policies that would aid with management efforts. Invasive species nihilism could make some stakeholders less likely to engage with managers because they have come to believe that management is pointless, and managers themselves may endure the stress of hearing that their work is not of value to people with this perspective. The effects that ISD may have on management are varied and depend largely on the type of framing of ISD being used. Similarly, the way that we respond to someone that we believe to be an invasive species denialist should be informed by the framing of ISD they are using.



“An understanding of these framings is also vital to respond to instances of ISD appropriately. Whether we are being confronted with anti-science contrarianism, environmental cynicism, or outbursts of nihilism, should inform our responses and our strategies to counter these positions.” (Stratton et al. 2022)

The framings of ISD explored in this research suggest that a diversity of interpretations of species movements, and value judgments about their impacts and the need for management, exist. This has the potential to problematize reductionist claims that all critiques of invasive species management are simply a denial of scientific facts. These results provide evidence that even when there is agreement on the impacts of invasive species on ecosystems, some stakeholders nevertheless deny the need for, or benefit of managing invasive species. This study further contributes to ongoing scholarly and practitioner conversations about the normative assumptions of invasive species biology and their implications for invasive species management and governance.

Research article:

Stratton NG, Mandrak NE, Klenk N (2022) From anti-science to environmental nihilism: the Fata Morgana of invasive species denialism. NeoBiota 75: 39-56. https://doi.org/10.3897/neobiota.75.90631

Image credits: diagram by NG Stratton; comic panels by NG Stratton, via material from Flickr (ChrisA1995, CC BY 2.0; Mike, CC BY-NC-SA 2.0; the-difference CC BY-NC-SA 2.0) and Studio Alternativi (Esetefania Quevedo).

Naturalists can mediate silent plankton invasions

Plankton can easily spread between water bodies on hydrobiological instruments if naturalists use inadequate biosecurity treatments in their work.

Homo sapiens is not only a great (perhaps the best) candidate for the world’s most invasive species award. Humans, due to their actions and technological wonders, are also at the forefront of good vectors for organismal dispersion. Can we break this inglorious streak?

“Because humans will continue to interact with terrestrial and aquatic environments, it is impossible to stop the human-aided dispersal of organisms completely. The best we can do is minimise the risk of human-mediated organism dispersal events by implementing adequate biosecurity methods in our activity” explains Dr Wejnerowski from Adam Mickiewicz University (Poland). 

Plankton sampling using net. Photo by Sandra Wejnerowska

“We should be aware that all our activities can affect biodiversity, and adequate biosecurity treatments should be applied whenever the risk of inadvertent spreading of organisms is non-zero” adds Dr Marcin Krzysztof Dziuba from the University of Michigan (United States of America).

Recently, a team of researchers from Adam Mickiewicz University, Istanbul University (Turkey), Åbo Akademi University (Finland), and the University of Michigan empirically proved that plankton net – a basic hydrobiological instrument of almost every aquatic scientist and water manager – is a good vector for the dispersal of various phyto- and zooplankton taxa, including species of high invasive potential. Nuisance, bloom-forming, also toxic filamentous cyanobacteria are efficient hitch-hikers, and they are able to successfully compete with native residents in the new environment.

Instructions for US citizens to avoid spreading invasive species during lake recreation. Photo by Marcin Krzysztof Dziuba

Apart from identifying hitch-hiking plankton on the net and its fate in the new environment, the paper they published in the journal NeoBiota also describes the most commonly used biosecurity treatments that naturalists worldwide use to prevent plankton spread between water bodies via the net.

Their findings sound disturbing: naturalists use inadequate or questionable biosecurity treatments. As revealed by the survey data, only 9% of plankton samplers clean plankton nets using disinfectant liquids after sampling, while a majority of people either rinse the net with distilled or tap water, immerse the net with an open outflow in the water body and let it dry, or do not care about the cleanness of the net after sampling at all.

Exemplary photos of some phyto- (A – Limnothrix redekei, B – Planktothrix agardhii, C – Pseudanabaena limnetica, D – Melosira varians, E – Desmodesmus armatus, F – Asterionella formosa, G – Tetradesmus obliquus) and zooplankton ( H – Keratella cochlearis f. typica) hitch-hikers on the plankton net. Micrograph I shows the plankton biomass on the surface of the plankton net after immersing the net with an open outflow in the water body (inadequate biosecurity treatment). Photos by Tumer Orhun Aykut and Łukasz Wejnerowski. Identification of organisms by Aleksandra Pełechata and Marcin Krzysztof Dziuba.

“Indeed, the reality presented in the paper is unsettling. It worries me when I think of how often I have accidentally facilitated dispersion of nuisance plankton and how much I contributed to the invasion of plankton taxa into new water bodies when using inappropriate biosecurity treatments in my fieldwork,” admits Dr Wejnerowski, and adds: “We do not mean to reinvent the wheel; the problem of aquatic organism dispersal through hydrobiological instruments is already known. For years, it was neglected despite some recalls from the scientific community. It comes back like a bad penny because it needs a complex solution from the society of aquatic naturalists. It should happen. After all, naturalists are a human line of defence, protection and rescue for nature.”

Research article:

Wejnerowski  Ł, Aykut TO, Pełechata A, Rybak M, Dulić T, Meriluoto J, Dziuba MK (2022) Plankton hitch-hikers on naturalists’ instruments as silent intruders of aquatic ecosystems: current risks and possible prevention. NeoBiota 73: 193-219. https://doi.org/10.3897/neobiota.73.82636

Genetically-enhanced biocontrols can help fight large invasive mammals

Genetic biocontrols could rapidly eradicate animals like rats, mice and rabbits. Others – like cats and foxes, would however take a lot longer.

But gene drives are not a one-size-fits-all solution

Invasive alien mammals can have catastrophic impacts on native flora and fauna, causing species extinctions and driving profound environmental change. Classical control methods such as poison baiting, trapping, or hunting are currently not feasible on a large scale, which is why researchers are looking for alternatives.

CRISPR-based genome engineering is often seen as a “silver bullet” for pest control. Despite the increasing interest in the development of this technology for invasive mammals like mice, rats, rabbits, feral cats, and foxes, studies have so far only focused on mice.

Scientists have been pondering whether genome editing technologies could help eradicate larger mammals, and if so, how long it would take.

Rabbit. Photo by Mark Philpott licensed under CC BY-NC 2.0.

In order to address these questions, a team of researchers from the University of Adelaide developed a mathematical model able to simulate the impact of gene drives on mammal populations at a landscape scale. Published in the open-access NeoBiota journal, their study is the first to estimate the time it would take to eradicate long-lived alien mammals.

Using CRISPR-Cas9 technology, the simulated gene drive relies on “molecular scissors” inserted into the Y-chromosome that target and slice up the X-chromosome at the right time during meiosis, so that only Y-chromosome carrying sperms are functional and can successfully fertilize the egg. In this way, the drive carrying males should only produce sons that also carry the molecular scissors on their Y-chromosome. Over multiple generations, females will become rarer and produce fewer offspring; as a result, the population size will fall.

Red fox. Photo by Rylee Isitt licensed under CC BY-SA 2.0.

This “X-shredder” drive has been successfully developed and demonstrated to suppress cage populations of malaria-carrying mosquitos, but has not yet been developed in mammals. The model shows that the X-shredder drive could potentially achieve landscape-scale eradication of mice, rats, rabbits, feral cats, and red foxes, but the probability of success and the time it would take to eradicate them vary greatly.

The researchers investigated the ability of the X-shredder drive to eradicate a population of 200,000 individuals of each species. “CRISPR-based gene drives offer novel solutions for controlling invasive alien species, which could ultimately extend eradication efforts to continental scales,” they concluded.

The method could be effective in small-sized pests, such as rodents and rabbits. The expected time to eradication is 18 years for mice, 19 years for rats, and 48 years for rabbits, with 90% population suppression achieved in around half those times.

However, the results suggest that gene drives are not a one-size-fits-all solution: they might not be so useful in larger species like cats and foxes.

“The probability of eradicating feral cats with gene drives is identical to flipping a coin, 50/50; and provided that the coin lands on the right side, it would take about 140 years to get rid of them,” says Dr. Aysegul Birand, part of the research team. “The probability of eradication is higher for foxes, but the wait is even longer.”

Original source: 

Birand A, Cassey P, Ross JV, Thomas PQ, Prowse TAA (2022) Scalability of genetic biocontrols for eradicating invasive alien mammals. NeoBiota 74: 93-103. https://doi.org/10.3897/neobiota.74.82394