Tag: invasive species

New improvements to how impacts of non-native species are assessed recommended

*A farmer sets a pheromone trap to fight tomato leaf miner. Photo by CABI.*

The Centre for Agriculture and Bioscience International (CABI) has led an international team of non-native species (NNS) specialists who have compiled a list of recommendations to improve the way in which the impact of a range of invasive pests – such as the tomato leaf miner Tuta absoluta – are assessed, potentially helping towards ensuring greater global food security.

Lead authors Dr Pablo González-Moreno and Dr Marc Kenis, Senior Researchers at CABI are two of 89 NNS experts from around the world who have collaborated on the paper, published in NeoBiota, that calls for ‘more robust and user-friendly’ impact assessment protocols to predict the impacts of new or likely invaders as well as to assess the actual impact of established species.

The manuscript is the outcome of an enormous collective effort using 11 different protocols to assess the potential impact of 57 NNS to Europe yielding a total of 2614 separate assessments. This unique dataset has allowed the authors to identify which are the main factors increasing the robustness of protocols and provide recommendations on how the robustness and applicability of protocols could be enhanced for assessing NNS impacts.

As reported in the study, entitled ‘Consistency of impact assessment protocols for Non-Native Species’, Dr González-Moreno and fellow scientists – from 80 institutions including the UK-based Centre for Ecology & Hydrology (CEH), University of Milan, University of Bern and Queens University Belfast – argue that ‘assessment of the realised or potential impacts of NNS is particularly important for the prioritization of management actions.’

Millions of the world’s most vulnerable people face problems with invasive weeds, insects and plant diseases, which are out of control and have a major impact on global prosperity, communities and the environment. Developing countries are disproportionately affected.

The global cost of the world’s 1.2 million invasive species is estimated at $1.4 trillion per year – close to 5 percent of global gross domestic product. In East Africa, five major invasive species alone cause $1 billion in economic losses to smallholder farmers each year.

The scientists believe that, currently, the large variety of metrics adopted to measure the impacts of invasive species undermines direct comparison of impacts across species, groups of taxa, localities or regions. They go on to argue that in general we have ‘little understanding of the patterns in consistency of impact scores across assessors and protocols, and more importantly, which factors contribute to high levels of consistency.’

Dr González-Moreno said,

“There is an increasing demand for robust and user-friendly impact assessment protocols to be used by professionals with different levels of expertise and knowledge.

Robust NNS impact protocols should ideally result in accurate and consistent impact scores for a species even if applied by different assessors, as long as they have the adequate expertise in the assessed species and context.

Several key factors should be taken into account when selecting or designing an NNS risk assessment protocol, such as the aim, the scope, the consistency and the accuracy of the outcomes, and the resources available to perform the assessment – for example time or information available.”

In compiling a list of recommendations for improved NNS impact protocols, Dr González-Moreno and the team of researchers used 11 different protocols to assess the potential impact of 57 species not native to Europe and belonging to a very large array of taxonomic groups (plants, animals, pathogens) from terrestrial to freshwater and marine environments.

They agree that using a ‘5-level scoring, maximum aggregation method and the moderation of expertise requirements’ offers a good compromise to reducing inconsistencies in research findings without losing discriminatory power or usability.

Dr González-Moreno added, “In general, we also advise protocol developers to perform sensibility tests of consistency before final release or adoption. This is crucial as if a protocol yields inconsistent outcomes when used by different assessors, then it is likely that decisions taken based on the results could be variable and disproportionate to the actual impacts.”

Original source:

González-Moreno P, Lazzaro L, Vilà M, Preda C, Adriaens T, Bacher S, Brundu G, Copp GH, Essl F, García-Berthou E, Katsanevakis S, Moen TL, Lucy FE, Nentwig W, Roy HE, Srėbalienė G, Talgø V, Vanderhoeven S, Andjelković A, Arbačiauskas K, Auger-Rozenberg M-A, Bae M-J, Bariche M, Boets P, Boieiro M, Borges PA, Canning-Clode J, Cardigos F, Chartosia N, Cottier-Cook EJ, Crocetta F, D’hondt B, Foggi B, Follak S, Gallardo B, Gammelmo Ø, Giakoumi S, Giuliani C, Guillaume F, Jelaska LS, Jeschke JM, Jover M, Juárez-Escario A, Kalogirou S, Kočić A, Kytinou E, Laverty C, Lozano V, Maceda-Veiga A, Marchante E, Marchante H, Martinou AF, Meyer S, Michin D, Montero-Castaño A, Morais MC, Morales-Rodriguez C, Muhthassim N, Nagy ZA, Ogris N, Onen H, Pergl J, Puntila R, Rabitsch W, Ramburn TT, Rego C, Reichenbach F, Romeralo C, Saul W-C, Schrader G, Sheehan R, Simonović P, Skolka M, Soares AO, Sundheim L, Tarkan AS, Tomov R, Tricarico E, Tsiamis K, Uludağ A, van Valkenburg J, Verreycken H, Vettraino AM, Vilar L, Wiig Ø, Witzell J, Zanetta A, Kenis M (2019) Consistency of impact assessment protocols for non-native species. NeoBiota 44: 1-25. https://doi.org/10.3897/neobiota.44.31650

Additional information:

The paper is based upon work from the COST Action TD1209: ALIEN Challenge. COST (European Cooperation in Science and Technology) is a pan-European intergovernmental framework. The mission of COST is to enable scientific and technological developments leading to new concepts and products and thereby contribute to strengthening Europe’s research and innovation capacities.

Dr Pablo González-Moreno was supported by the CABI Development Fund (with contributions from ACIAR (Australia) and DFID (UK) and by Darwin plus, DPLUS074 ‘Improving biosecurity in the SAUKOTs through Pest Risk Assessments’.

Text originally published by CABI.

Non-native pest-controlling wasp identified in Canada prior to formal approval

A samurai wasp (Trissolcus japonicus) lays an egg inside a brown marmorated stink bug (Halyomorpha halys) egg. The samurai wasp’s offspring will develop inside the pest’s egg and emerge as an adult wasp. Photo by Warren Wong.

Thought to be Canada’s most promising potential defense against the brown marmorated stink bug – a globally spreading agricultural pest native to Asia – the samurai wasp (another species from Asia and natural parasitoid of the former) has been considered for future release in the country in recent years.

However, prior to any formal decision and regulatory approval, the parasitoid, which is known to be specialized on stink bug eggs, was identified at a heavily infested site in Chilliwack, British Columbia, during a survey of the local enemies of the bug, conducted by a research team led by Dr. Paul Abram of Agriculture and Agri-Food Canada. Their findings are published in the open-access Journal of Hymenoptera Research.

Native to China, Japan, Taiwan and the Korean peninsula, the brown marmorated stink bug (Halyomorpha halys) has already established in areas of the United States and Europe and continues to spread. It is highly damaging to a wide range of vegetable and fruit crops, including peaches, apples, pears, soybeans, cherries, raspberries and pears. Curiously, those infested areas in both the USA and Europe also saw the arrival of the samurai wasp (Trissolcus japonicus) amid assessments whether releasing samurai wasps in the wild should be warranted.

“Classical (importation) biological control of invasive pests, where natural enemies are imported and intentionally introduced from a pest’s area of origin, involves years of research to assess risks and benefits of proposed introductions, followed by regulatory approval,” explain the researchers in their paper.

“However, there is increasing recognition that unintentional introductions of natural enemies are probably common, introducing a high level of uncertainty to the regulatory process for biological control introductions.”

In two consecutive years (2017 and 2018), the team of Dr Abram placed a total of 1,496 egg masses (41,351 eggs) of brown marmorated stink bugs at 16 field sites in coastal and interior British Columbia – already known to host large and well-established breeding populations of the species – in order to monitor and identify the local enemies of the pest. Later on, when the researchers retrieved the eggs and studied their parasitoids, they found three native wasp species, but their parasitism appeared largely unsuccessful.

*Female samurai wasp (Trissolcus japonicus) collected from Chilliwack, British Columbia. Photo by Elijah Talamas.*

According to the scientists, as well as previous studies conducted in both the USA and Europe, native wasps would often lay their eggs in those of the brown marmorated stink bug, but their larvae would rarely complete development. Even when they emerged, they were unlikely to produce their own offspring.

In one of the egg masses, however, the scientists noted that all eggs had been parasitized and, moreover, each produced a viable wasp. Later, the offspring would register a success of >90% in parasitizing brown marmorated stink bug eggs. Following these observations, the team identified these parasitoids as samurai wasps.

While the species is currently being redistributed within some US states on purpose, samurai wasp populations advancing to other localities suggest that much like its host, the parasitoid is also becoming a “global invader”. Therefore, it is quite possible that the samurai wasps in British Columbia have simply crossed a distance of >400 km from nearby Washington State, and the wasp is still at the early stages of its establishment in Canada.

“Nonetheless, the detection of this exotic biological control agent in Canada concurrently with regulatory review of its intentional importation and release is emblematic of the current uncertainty around regulatory control on the movement of biological control agents across borders,” comment the authors of the study.

Field surveys and extensive analyses are currently underway to track the establishment and biological control impact of the samurai wasp in Canada and also reveal how the species ended up in British Columbia.

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Original source:

Abram PK, Talamas EJ, Acheampong S, Mason PG, Gariepy TD (2019) First detection of the samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae), in Canada. Journal of Hymenoptera Research 68: 29-36. https://doi.org/10.3897/jhr.68.32203

The Widow Next Door: Where is the globally invasive Noble False Widow settling next?

*Noble false widow spider (Steatoda nobilis) at a public bus stop in the seaside resort of Lyme Regis, southern England. Photo by Rainer Breitling.*

Spiders are one of the most successful groups of ‘invaders’ on the planet. Out of over 47,000 species of spiders known today, there are some that tend to follow humans across the globe and settle in habitats far away from their native homelands. A particularly notorious example is the species Steatoda nobilis, the Noble False Widow spider.

Originating from Madeira (Portugal) and the Canary Islands (Spain), the Noble False Widow has been rapidly spreading around the globe over the last few decades. While the species is already well established in Western Europe and large parts of the Mediterranean area, it has recently spread into California, South America and Central Europe. Meanwhile, its populations in England, where the spider used to be restricted to the very southern parts of the country, are now seen to experience a sudden expansion northwards.

As its name suggests, this is a relatively large species that resembles the well-known Black Widow and can inflict a painful – yet mostly harmless to humans – bite. Naturally, its ‘arrival’ causes widespread concerns and public disruptions. Specifically, the Noble False Widow poses a threat to native faunas, since it can prey on nearly every smaller animal thanks to its potent venom and sturdy webs.

Recently, experts and non-professional citizen scientists joined forces to reconstruct the invasion path of the Noble False Widow in Europe and the Americas, so that they could identify patterns and predict which regions are likely to be the next colonised by the spider.

By combining data from museum collections and the Spider and Harvestman Recording Scheme of the British Arachnological Society with published literature and their own observations from England, Germany, France and Ecuador, the researchers provided an unprecedented detailed view of the expansion of the Noble False Widow. The study, conducted by Tobias Bauer (State Museum of Natural History Karlsruhe), Stephan Feldmeier (Trier University), Henrik Krehenwinkel (Trier University and University of California Berkeley), Rainer Breitling (University of Manchester) and citizen scientists Carsten Wieczorrek and Nils Reiser, is published in the open-access journal Neobiota.

While it had largely been assumed that the Noble False Widow turned up in Europe along with bananas traded from the Canary Islands, a new look at the data revealed that the spiders have most likely been transported via imports of ornamental plants. Further, rather than the result of climate change, the establishment of the species across new, large territories is rather linked to the fact that these habitats all share similar conditions to the spider’s native localities.

“Similar suitable False Widow habitats occur in quite specific regions all around the globe,” explain the researchers. “Most importantly, South Africa, some areas in southern Australia, and a large part of New Zealand turn out to be highly likely targets for future invasions, unless appropriate import control measures are implemented.”

*Global prediction of suitable regions for the Noble False Widow (Steatoda nobilis). Image by Stephan Feldmeier & Tobias Bauer.*

In conclusion, the authors call for enhanced monitoring of the Noble False Widow as well as its still little known ecological impact on the environment in newly colonised areas. They also urge scientists in the predicted potential invasion target regions to search for specimens, especially in coastal cities.

Original source:

Bauer T, Feldmeier S, Krehenwinkel H, Wieczorrek C, Reiser N, Breitling R (2019) Steatoda nobilis, a false widow on the rise: a synthesis of past and current distribution trends. NeoBiota 42: 19-43. https://doi.org/10.3897/neobiota.42.31582

Scientists forecast where is the highly invasive fall armyworm to strike next

*The fall armyworm is the larvae of the fall armyworm moth species Spodoptera frugiperda. Photo by Centre for Agriculture and Bioscience International (CABI).*

Staple and economically important crops throughout the world could be at serious risk if efficient measures are not taken soon

Known to be feeding on many economically important crops cultured across the world, including maize, rice, sugarcane, sorghum, beet, tomato, potato, cotton and pasture grasses, the larvae of the native to the Americas fall armyworm moth seem to have already found a successful survival strategy in a diverse and changing world.

Furthermore, having taken no longer than 2 years to invade and spread throughout most of sub-Saharan Africa, the pest has already demonstrated its huge potential in severely affecting livelihoods around the globe.

A recent study in the open-access journal NeoBiota, conducted by Dr Regan Early of Exeter University, United Kingdom and her colleagues at the Centre for Agriculture and Bioscience International: Dr Pablo González-Moreno, Sean T. Murphy and Roger Day, looks into the factors and likelihood for the fall armyworm (Spodoptera frugiperda) to spread to other regions and continents.

Invasion progress

The alarming reports started in January 2016 when major outbreaks of fall armyworms were registered in Nigeria and Ghana, preceding signals from Benin, Sao Tomé and Togo shortly after. By September 2017, the pest had already been confirmed in 28 sub-Saharan African countries, with nine states expected to follow suit.

While unaided dispersal of the species in Africa is considered unlikely, it is speculated that the pest had arrived on a passenger flight from America. To back this theory, the researchers point out that the first countries to house the invader are also the major air transportation hubs in Africa and have warm, moist climate similar to those in the pest’s natural habitat.

In the aftermath, recent estimates point to up to 50% maize yield loss in Africa attributed to the fall armyworm. However, scientists believe that the species is far from finished spreading and is highly likely to invade new continents.

Who’s next?

To find what makes a region an inviting new habitat for the fall armyworm, hence which countries face the highest threat of future invasions, the researchers looked into both the native and African distributions of the species, and the effects different temperatures and precipitation levels have on it.

Having concluded that the lowest temperatures and the maximum amount of rain play the main role in determining whether the fall armyworm is to establish in a certain region, the scientists concluded that South and Southeast Asia, as well as Australia face the most serious risk, since their climate is very similar to the one preferred by the pest.

However, the authors of the study remind that this forecast shall in no way be taken with a sigh of relief by countries with milder climatic conditions. While the moth needs particular temperature and precipitation amplitudes at its year-round habitat, it could easily travel back and forth up to several hundred kilometres during its seasonal migrations. Therefore, if the fall armyworm establishes in North Africa, it could migrate to Europe during the warmer months, just like it has already been observed to travel from its year-round localities in Argentina, Texas and Florida all the way to Canada’s Québec and Ontario in the north.

The increasing transportation and international trade are also likely to facilitate the further spread of the fall armyworm outside Africa. The scientists conclude that, given the current travel air routes, it is Australia, China, India, Indonesia, Malaysia, Philippines and Thailand which are at high risk of becoming the pest’s new habitat.

*The map illustrates the likelihood of the establishment of the fall armyworm if introduced at different parts of the world. Image by Regan Early.*

What’s next?

Having concluded that there is a considerable potential for near global invasion and seasonal migration of fall armyworm, the scientists call for vigilance from farmers and programme managers alike. They remind that early detection of small larvae is crucial, since it is only at this stage that chemical insecticides would work effectively.

“As fall armyworm has huge potential to affect staple and economic crops globally, we urgently need information on the pest’s potential distribution and environmental limitations,” comment the researchers.

“Management decisions would be improved by further research on fall armyworm’s seasonal migration and population dynamics and the environmental dependency of interactions with other species.”

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Original source:

Early R, González-Moreno P, Murphy ST, Day R (2018) Forecasting the global extent of invasion of the cereal pest Spodoptera frugiperda, the fall armyworm. NeoBiota 40: 25-50. https://doi.org/10.3897/neobiota.40.28165

A preprint of the study was published earlier on bioRxiv.

Tiny moth from Asia spreading fast on Siberian elms in eastern North America

In 2010, moth collector James Vargo began finding numerous specimens of a hitherto unknown pygmy moth in his light traps on his property in Indiana, USA. When handed to Erik van Nieukerken, researcher at Naturalis Biodiversity Center (Leiden, the Netherlands) and specialist in pygmy moths (family Nepticulidae), the scientist failed to identify it as a previously known species.

*These are male specimens of the studied leaf mining moth Stigmella multispicata collected from Iowa, USA.*

Then, Erik found a striking similarity of the DNA barcodes with those of a larva he had recently collected on Siberian elm in Beijing’s botanical garden. At the time, the Chinese specimen could not be identified either.

In October 2015, Daniel Owen Gilrein, entomologist at Cornell Cooperative Extension of Suffolk County (New York, USA), received samples of green caterpillars seen to descend en masse from Siberian elm trees in Sagaponack, New York. He also received leafmines from the same trees.

Once they joined forces, the researchers did not take long to find out that the specimens from James Vargo and the caterpillars from New York belonged to one and the same species. The only thing left was its name.

Following further investigation, the scientists identified the moth as Stigmella multispicata – a pygmy moth described in 2014 from Primorye, Russia, by the Lithuanian specialists Agne Rociene and Jonas Stonis.

“Apparently, this meant that we were dealing with a recent invasion from East Asia into North America,” explains Erik.

Once the researchers had figured out how to identify the leafminer, they were quick to spot its existence in plenty of collections and occurrence reports from websites, such as BugGuide and iNaturalist.

With the help of Charley Eiseman, a naturalist from Massachusetts specializing in North American leafminers, the authors managed to conclude the moth’s existence in ten US states and two Canadian provinces. In most cases, the species was found on or near Siberian elm – another species transferred from Asia to North America.

Their study is published in the open access journal ZooKeys.

Despite the oldest records dating from 2010, it turned out that the species had already been well established at the time. The authors suspect that the spread has been assisted by transport of plants across nurseries.

“Even though Stigmella multispicata does not seem to be a real problem, it would be a good idea to follow its invasion over North America, and to monitor whether the species may also attack native elm species,” the researchers point out.

Interestingly, in addition to the newly identified moth, the Siberian elms in North America have been struggling with another, even more common, invasive leafminer from Asia: the weevil species Orchestes steppensis. The beetle had been previously misnamed as the European elm flea weevil.

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Original source:

van Nieukerken EJ, Gilrein DO, Eiseman CS (2018) Stigmella multispicata Rociene & Stonis, an Asian leafminer on Siberian elm, now widespread in eastern North America (Lepidoptera, Nepticulidae). ZooKeys 784: 95-125. https://doi.org/10.3897/zookeys.784.27296

How did coyotes conquer North America?

Coyotes now live across North America, from Alaska to Panama, California to Maine. But where they came from, and when, has been debated for decades.

Using museum specimens and fossil records, researchers from the North Carolina Museum of Natural Sciences and North Carolina State University have produced a comprehensive (and unprecedented) range history of the expanding species that can help reveal the ecology of predation as well as evolution through hybridization. Their findings are published in the open access journal ZooKeys.

The geographic distribution of coyotes has dramatically expanded since 1900, spreading across much of North America in a period when most other mammal species have been declining. Although this unprecedented expansion has been well-documented at the state/provincial scale, continent-wide picture of coyote spread been coarse and largely anecdotal. A more thorough compilation of available records was needed.

“We began by mapping the original range of coyotes using archaeological and fossil records,” says co-author Dr. Roland Kays, Head of the Museum’s Biodiversity Lab and Research Associate Professor in NC State’s Department of Forestry and Environmental Resources. “We then plotted their range expansion across North America from 1900 to 2016 using museum specimens, peer-reviewed reports, and game department records.”

In all, Kays and lead author James Hody, a graduate student at NC State University, reviewed more than 12,500 records covering the past 10,000 years for this study.

Their findings indicate that coyotes historically occupied a larger area of North America than generally suggested in the literature. Previous maps, as it turns out, had ancient coyotes only located across the central deserts and grasslands. However, fossils from across the arid west link the distribution of coyotes from 10,000 years ago to specimens collected in the late 1800s, proving that their geographic range was not only broader but had been established for hundreds, perhaps thousands of years, which also contradicts some widely-cited descriptions of their historical distribution.

It wasn’t until approximately 1920 that coyotes began their expansion across North America. This was likely aided by an expansion of human agriculture, forest fragmentation, and hybridization with other species. Eastern expansion, in particular, was aided by hybridization with wolves and dogs, resulting in size and color variation among eastern coyotes.

Before too long, coyotes may no longer be just a North American species. Kays notes that coyotes are continually expanding their range in Central America, having crossed the Panama Canal in 2010. Active camera traps are now spotting coyotes approaching the Darien Gap, a heavily forested region separating North and South America, suggesting that they are at the doorstep of South America.

“The expansion of coyotes across the American continent offers an incredible experiment for assessing ecological questions about their roles as predators, and evolutionary questions related to their hybridization with dogs and wolves,” adds Hody.

“By collecting and mapping these museum data we were able to correct old misconceptions of their original range, and more precisely map and date their recent expansions.”

“We hope these maps will provide useful context for future research into the ecology and evolution of this incredibly adaptive carnivore,” he concludes.

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(Originally published on Eurekalert! by North Carolina Museum of Natural Sciences.)

Original source:

Hody JW, Kays R (2018) Mapping the expansion of coyotes (Canis latrans) across North and Central America. ZooKeys 759: 81–97. https://doi.org/10.3897/zookeys.759.15149

Scientists dive into museum collections to reveal the invasion route of a small crustacean

Biological invasions are widely recognised as one of the most significant components of global change. Far-reaching and fast-spreading, they often have harmful effects on biodiversity.

Therefore, acquiring knowledge of potentially invasive non-native species is crucial in current research. In particular, it is important that we enhance our understanding of the impact of such invasions.

To do so, Prof Sabrina Lo Brutto and Dr Davide Iaciofano, both working at the Taxonomy Laboratory of the University of Palermo, Italy, performed research on an invasive alien crustacean (Ptilohyale littoralis) known to have colonised the Atlantic European Coast. Their findings are published in the open access journal ZooKeys.

The studied species belongs to a group of small-sized crustaceans known as amphipods. These creatures range from 1 to 340 mm in length and feed on available organic matter, such as dead animals and plants. Being widely distributed across aquatic environments, amphipods have already been proven as excellent indicators of ecosystem health.

While notable for their adaptability and ecological plasticity, which secure their abundance in various habitats, these features also make amphipods especially dangerous when it comes to playing the role of invaders.

Having analysed specimens stored at the Museum of Natural History of Verona and the Natural History Museum in Paris, the scientists concluded that the species has colonised European waters 24 years prior to the currently available records.

The problem was that, back in 1985, when the amphipod was first collected from European coasts, it was misidentified as a species new to science instead of an invader native to the North American Atlantic coast.

A closer look into misidentified specimens stored in museum collections revealed that the species has been successfully spreading along the European coastlines.

Male of the invasive amphipod species (*Ptilohyale littoralis*), sampled in October 2015, from Bay of Arcachon, France.

Moreover, it was predicted that the amphipod could soon reach the Mediterranean due to the high connectivity between the sea and the eastern Atlantic Ocean through the Straits of Gibraltar – a route already used by invasive marine fauna in the past.

In the event that the invader reaches the Mediterranean, it is highly likely for the crustacean to meet and compete with a closely related “sister species” endemic to the region. To make matters worse, the two amphipods are difficult to distinguish due to their appearance and behaviour both being extremely similar.

However, in their paper, the scientists have also provided additional information on how to distinguish the two amphipods – knowledge which could be essential for the management of the invader and its further spread.

The authors believe that their study demonstrates the importance of taxonomy – the study of organism classification – and the role of natural history collections and museums.

“Studying and monitoring biodiversity can acquire great importance in European aquatic ecosystems and coastal Mediterranean areas, where biodiversity is changing due to climate change and invasions of alien species,” Prof Lo Brutto says. “In this context, specific animal groups play a crucial role in detecting such changes and they, therefore, deserve more attention as fundamental tools in biodiversity monitoring.”

“Regrettably, the steadily diminishing pool of experts capable of accurately identifying species poses a serious threat in this field.”

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Original source:

Lo Brutto S, Iaciofano D (2018) A taxonomic revision helps to clarify differences between the Atlantic invasive Ptilohyale littoralis and the Mediterranean endemic Parhyale plumicornis(Crustacea: Amphipoda). ZooKeys, 754: 47-62. https://doi.org/10.3897/zookeys.754.22884

Double trouble: Invasive insect species overlooked as a result of a shared name

An invasive leaf-mining moth, feeding on cornelian cherry, has been gradually expanding its distributional range from its native Central Europe northwards for a period likely longer than 60 years. During that period, it has remained under the cover of a taxonomic confusion, while going by a name shared with another species that feeds on common dogwood.

To reproduce, this group of leaf-mining moths lay their eggs in specific plants, where the larvae make tunnels or ‘mines’, in the leaves. At the end of these burrows, they bite off an oval section, in which they can later pupate. These cutouts are also termed ‘shields’, prompting the common name of the family, the shield-bearer moths.

During a routine study into the DNA of leaf-mining moths, Erik van Nieukerken, researcher at Naturalis Biodiversity Center, Leiden, the Netherlands, discovered that the DNA barcodes of the species feeding on common dogwood and cornelian cherry were in fact so different that they could only arise from two separate species. As a result, Erik teamed up with several other scientists and amateur entomologists to initiate a more in-depth taxonomic study.

Curiously, it turned out that the two species had been first identified on their own as early as in 1899, before being described in detail by a Polish scientist in the 50s. Ironically, it was another Polish study, published in the 70s, that regarded the evidence listed in that description as insufficient and synonymised the two leaf-miners under a common name (Antispila treitschkiella).

Now, as a result of the recent study undertaken by van Nieukerken and his collaborators, the two moth species – Antispila treitschkiella and Antispila petryi – have their diagnostic features listed in a research article published in the open access journal Nota Lepidopterologica.

“We now establish that the species feeding on common dogwood, A. petryi, does not differ only in its DNA barcode, but also in characters of the larva, genitalia and life history,” explains Erik van Nieukerken. “A. petryi has a single annual generation, with larvae found from August to November, whereas A. treitschkiella, which feeds on cornelian cherry, has two generations, with larvae occurring in June-July and once again between September and November.”

While van Nieukerken and his team were working on the taxonomy of the moths, David C. Lees of the Natural History Museum, London, spotted a female leaf-miner in the Wildlife Garden of the museum. Following consultation with van Nieukerken, it turned out that the specimen in question was the first genuine A. treitschkiella ever to be found in Britain. Subsequently, the research groups decided to join forces, leading to the present discovery.

Despite the lack of data for the British Isles, it is already known that, in continental Europe, the cornelian cherry-feeding species had established in the Netherlands and much of Germany in the 1990s.

With common dogwood being widely planted, it is now suspected that A. petryi has recently reached Sweden and Estonia, even though there was no previous evidence of the leaf-miner expanding its range.

“This discovery should provoke the attention of gardeners and other members of the public alike to the invasive leafminers attacking some of our much admired trees and shrubs, as we have demonstrated for the cornelian cherry – a species well-known for its showy red berries in the autumn,” says David Lees.

“Especially in Britain, we hope that they check their photos for the conspicuous leaf mines, recognisable by those oval cutouts, to see if they can solve the mystery of when the invasion, which is now prominent on cornels around London, actually started, and how fast it progresses. Citizen scientists can help.”

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Original source:

van Nieukerken EJ, Lees DC, Doorenweerd C, Koster S(JC), Bryner R, Schreurs A, Timmermans MJTN, Sattler K (2018) Two European Cornus L. feeding leafmining moths, Antispila petryi Martini, 1899, sp. rev. and A. treitschkiella (Fischer von Röslerstamm, 1843) (Lepidoptera, Heliozelidae): an unjustified synonymy and overlooked range expansion. Nota Lepidopterologica 41(1): 39-86. https://doi.org/10.3897/nl.41.22264

A race against pine: Wood-boring wasp in North America threatened by a Eurasian invader

Invasive species have diverse impacts in different locations, including biodiversity loss, as a result of native species being outcompeted for similar resources. A U.S. research team, led by Dr. Ann Hajek, Cornell University, studied the case of an aggressive Eurasian woodwasp that has recently established in North America and poses a threat to a native species. Their study is published in the open-access journal NeoBiota.

Most woodwasps play an essential part in the forest ecosystem, as they decompose wood, preferring dying or felled trees. They do so by laying their eggs in the wood underneath the tree bark. Curiously, the wasps also deposit a symbiotic fungus and venom that shuts down the tree’s defenses. As the tree weakens, the fungal infestation begins and the the tree starts to rot. When the eggs hatch, the larvae feed on the rotten wood before they emerge. This relationship is called obligate since the survival of the wasp is impossible without the fungal infestation.

Originating from Eurasia, the presence of the invasive species is dangerous because it can kill healthier pines. It has long been established in the southern hemisphere causing economic issues due to its attacks on pines. While pines have been introduced to that part of the world, they are native to North America, where the invasive wasp could be far more devastating.

Now that the invasive woodwasp has already been identified in the States, the scientists seek to find a way to protect its frail competitor, reporting a rapid decline in the North American species.

“We would often observe both species emerging from the same infested pine trees, but the ratios changed with time,” explains Dr. Ann Hajek.

“Shortly after the invasive colonizes an area, the native wasps emerging from the trees would equal the invasive. However, a few years later, the natives started to get fewer and fewer.”

It turned out that the Eurasian woodwasp has larger venom glands and produces more eggs, thanks to its greater body size. Furthermore, it emerges earlier than the North American species, so that it can find and colonize the most suitable trees first. By the time the native species lays its eggs, the authors speculate, most of the preferred trees are already occupied by the invasive, leaving a reduced supply of habitat for the newcomer’s larvae.

“Woodwasps are difficult to study and their biologies are generally poorly understood,” note the authors. “While the native species appears to be outcompeted from pines that both species prefer, it is possible that populations of the native can be sustained in trees less desirable to the invasive or unavailable during the time and place that the invasive is present.”

The scientists call for additional research on the native woodwasp in southeastern pine forests in USA, before the invaders spread to that area with extensive pine forests.

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Original source:

Hajek AE, Henry JC, Standley CR, Foelker CJ (2017) Comparing functional traits and abundance of invasive versus native woodwasps. NeoBiota 36: 39-55. https://doi.org/10.3897/neobiota.36.14953

Poison ivy an unlikely hero in warding off exotic invaders?

Dozens of studies have looked at the effects of Japanese knotweed on natural communities in Europe and North America. Yet Bucknell University professor Chris Martine still felt there was something important to learn about what the plant was doing along the river in his own backyard.

“The more time I spent in the forests along the Susquehanna River, the more it seemed like something was really going wrong there,” said Martine. “In addition to the prevalence of this single invasive species, it looked like the very existence of these forests was under threat.”

What Martine noticed was similar to what local nature lovers and biologists with the Pennsylvania Natural Heritage Program were also starting to see: these forests, specifically those classified as Silver Maple Floodplain Forests, were not regenerating themselves where knotweed had taken a foothold.

In a new study published in the open access Biodiversity Data Journal, Martine and two recent Bucknell alumni conclude that Japanese knotweed has not only excluded nearly all of the native understory plant species in these forests, but it has prevented the trees already established in the canopy from leaving behind more of themselves.

“If you were to fly over these forests, or even look at a Google Earth image, you’d see a nice green canopy along the river consisting of mature silver maples, river birches, and sycamores,” explained Martine. “But below that canopy there is almost nothing for tens of feet before you reach an eight-to-twelve-foot-tall thicket of knotweed. Few new trees have been able to grow through that in the last 50-60 years and our surveys found that seedlings of these species are quite rare.”

The authors suggest that as mature trees die of natural causes over the next several decades and are not replaced, these systems will shift from tree-dominated riverbank habitats to “knotweed-dominated herbaceous shrublands” incapable of supporting a rich diversity of insects, birds, and other wildlife. Loss of trees in these habitats could likely also lead to riverbank erosion and increase the severity of flood events.

The few places where knotweed has not taken over offer a bit of hope, however, from an unlikely hero: poison-ivy, which Martine calls “perhaps the least popular plant in America.”

“What we see in the data is that poison-ivy often trades understory dominance with knotweed. That is, when knotweed isn’t the big boss, poison-ivy usually is. The difference is that whereas knotweed knocks everyone else out of the system, poison-ivy is more of a team player. Many other native plants can co-occur with it and it even seems to create microhabitats that help tree seedlings get established.”

The prevalence of poison-ivy in these sites didn’t go unnoticed by undergraduate Anna Freundlich, who collected most of the plant community data — more than 1,000 data points — in a single summer as a research fellow.

“Anna developed a pretty serious methodology for avoiding a poison-ivy rash that included long sleeves, long pants, gloves, duct tape, and an intense wash-down protocol,” said her research advisor, “and even after crawling through the plant for weeks she managed to never once get a rash.”

Martine cautions against too much optimism regarding the chances of one itch-inducing native plant saving the day, however.

“Righting this ship is going to require eradicating knotweed from some of these sites, and that won’t be easy work. It will take some hard manual labor. But it’s worth doing if we want to avoid the imminent ecological catastrophe. These forests really can’t afford another half-century of us letting knotweed run wild.”

Freundlich is a now pursuing a Master’s degree in plant ecology at the University of Northern Colorado. Lead author Matt Wilson, a Bucknell Master’s student at the time of the study who analyzed the dataset, now works for the Friends of the Verde River in Cottonwood, AZ.

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Original source:

Wilson M, Freundlich A, Martine C (2017) Understory dominance and the new climax: Impacts of Japanese knotweed (Fallopia japonica) invasion on native plant diversity and recruitment in a riparian woodland. Biodiversity Data Journal 5: e20577. https://doi.org/10.3897/BDJ.5.e20577

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About Japanese knotweed:

Japanese knotweed is considered to be one of the toughest, most damaging and insidious plants in the world. Native to East Asia, the species has already established successfully in many parts throughout North America and Europe, where it can easily grow and invade private properties and homes. It is hardy enough to penetrate patios, house foundations and concrete. Given it spreads easily and can grow underground to a depth of 3 metres with a horizontal range of up to 7 metres, it is extremely difficult to eradicate and its treatment requires special attention. To find advice on recognition, hazards and treatment, you can check out The Ultimate Japanese Knotweed Guide.