introduced species

“Invasional Mutualism” Between Honey Bees and Myrtle Rust Pathogen

New research from NeoBiota uncovers an invasional mutualism between Western honey bees and myrtle rust, with potentially troubling consequences for Australia’s native ecosystems.

Every year on May 20th, the world celebrates World Bee Day, a date chosen to honour Anton Janša, an 18th-century pioneer of modern beekeeping who was born on this day in Slovenia, a country where beekeeping has been a cherished tradition for centuries. This year’s theme, “Bee Together for People and the Planet,” puts the spotlight on the partnership between humans and bees, and how collaboration, tradition, and innovation can help secure a sustainable future for both.

At Pensoft, we’re marking the occasion by shining a light on a threat that often goes unnoticed: the destabilisation of pollination networks. As ecosystems change and pathogens spread, sometimes carried by the very pollinators we rely on, the delicate web of relationships between plants and their pollinators is under pressure. Understanding bees and other pollinators as potential carriers of invasive plant diseases is becoming an increasingly important piece of the conservation puzzle.

Surprising Interaction

Apis mellifera and myrtle rust fungus invasional mutualism — Apis mellifera on leaves with myrtle rust. Photo credit to Geoff S Pegg.

New research published in NeoBiota has found that the Western honey bee – an introduced species to Australia – and the devastating, invasive plant fungus known as myrtle rust (Austropuccinia psidii) may have formed a mutually beneficial relationship known as an “invasional mutualism.”

Myrtle rust is notorious for devastating ecologically and culturally significant native plants in the Myrtaceae family, putting 17% of Australia’s endemic vegetation at risk. While rust fungi generally rely strictly on wind to spread, researchers discovered that bees may actively forage on the bright yellow fungus spores, packing them into their pollen baskets and carrying them back to the hive just as they would regular pollen.

Researcher taking samples from a beehive. Photo credit to Caroline Hauxwell.
Beehive in the forest. Photo credit to Caroline Hauxwell.

Through a series of experiments, the team made three significant findings. Firstly, the rust spores proved to be quite nutritious. They contained over 22% protein and all 10 essential amino acids, meeting the threshold required for bee colonies to survive. In fact, the fungus matched the nutritional quality of high-value floral pollen, like willow pollen.

In laboratory feeding trials, larvae raised on a diet of myrtle rust spores grew up perfectly healthy, developing at the same speed and reaching similar body weights as bees raised on a traditional high-quality pollen diet. As the researchers explain:

These findings suggest that spore foraging may not be an aberration, but a viable foraging strategy for honey bees.

And perhaps the most alarming discovery is that the myrtle rust spores remain viable and capable of causing new plant infections for at least nine days inside a beehive which could pose significant biosecurity risks

A Devastating Ecological Feedback Loop

Beehive samples taking — Taking samples from a beehive. Photo credit to Caroline Hauxwell.

This discovery challenges the assumption that invasive species always act independently, and it carries major environmental consequences. As myrtle rust kills off keystone taxa in the Myrtaceae family, such as eucalypts, paperbarks, and other ecologically and culturally significant species, particularly in Australia, fewer flowers and less pollen become available for bees to forage on. Beyond the direct biodiversity loss, as the fungus kills these plants, fewer flowers and less pollen are available for the bees.

Under such conditions, bees may increasingly turn to alternative protein sources, such as fungal urediniospores,
the researchers explain.

This could set off a devastating ecological feedback loop.

“Over time, this dynamic may destabilise plant-pollinator networks and forest regeneration, particularly in regions with high Myrtaceae endemism.” They add: “While generalist foragers like A. mellifera may buffer their colony health by switching to spores or non-Myrtaceae pollen sources, the long-term ecological cost could be substantial, especially for specialist pollinators that lack such flexibility.“

The risks extend beyond ecosystems. Because spores remain viable inside a hive for over a week, commercial beehives – regularly transported across the country over three to seven days to pollinate crops – now represent a significant pathway for human-assisted spread of the pathogen.

As the lead author, Sacchi Shin-Clayton (University of Cambridge) emphasises:

Apis mellifera is an introduced species used as a commercial pollination agent worldwide, and shifting honey bee colonies between agricultural sites to boost pollination has become a standard practice. This reliance on honey bee colonies and shifting between multiple sites is quite concerning, given the demonstrated interaction between A. mellifera and myrtle rust, and its longevity within colonies.

Despite this, current biosecurity strategies for managing myrtle rust do not account for the movement of commercial beehives, leaving a critical gap in disease management approaches.

We propose that honey bees be explicitly considered in both epidemiological models and the formulation of management and containment strategies,
the researchers urge.

Recognising pollinators as potential vectors of invasive plant pathogens is an essential next step – one that could prove critical for protecting Australia’s vulnerable native forests.

This World Bee Day is a timely reminder that our relationship with bees is more complex than it might seem. Protecting them and the ecosystems they move through will require us to understand that complexity better.

Original source:

Shin-Clayton S, Mortensen AN, Beggs JR, Buxton MN, Hauxwell C, Bateson MF, Jochym M, Pegg GS, Pattemore DE (2026) Honey bees as potential vectors of the invasive rust pathogen Austropuccinia psidii: nutritional mutualism and implications for pathogen spread. NeoBiota 106: 75-90. https://doi.org/10.3897/neobiota.106.169027

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Alien land snail species are increasing exponentially

A new study compiles an overview of the exponential increase and dynamic spread of land snail species introduced to Europe and the Mediterranean.

Invasive land snail species can displace native species and harm human health. A recent study by the Leibniz Institute for Biodiversity Change Analysis (LIB) compiles an overview of the exponential increase and dynamic spread of land snail species introduced to Europe and the Mediterranean from other continents.

*Laevicaulis alte*, an invasive species from tropical Africa that was introduced into Egypt in 2018. © Reham F. Ali

To date, there is a lack of information for the spread of alien species, especially invertebrates such as snails. “Despite efforts to compile lists of alien species, there is not even a well-documented inventory of alien invertebrate species for Europe,” emphasizes Prof. Dr. Bernhard Hausdorf, section leader Mollusca at LIB. His study, just published in the journal NeoBiota, provides a basis for decisions on further measures to control or eradicate introduced populations.

Alien land snail species in the Western Palaearctic Region: Zonitoides arboreus, Hawaiia minuscula, Guppya gundlachii, Polygyra cereolus

Land snails play a supporting role in ecosystems. They decompose decaying plants and thus play an important role in nutrient cycling and soil formation. However, more and more species are being spread beyond their native range, usually by humans, sometimes intentionally, but often unintentionally by goods or travellers.

The study examines 22 land snail species introduced to Europe and the Mediterranean from other continents. Most of them are small, live on decaying plant parts and apparently cause few problems. In contrast, carnivorous species can threaten native species; and species that feed on living plants can cause damage to agriculture. Some even serve as hosts and vectors of parasites that can cause brain encephalitis, for example, and thus can indirectly harm human health.

Alien land snail species in the Western Palaearctic Region: *Paralaoma servilis* and *Helicodiscus parallelus*.

Harmful species include the Laevicaulis species recently introduced to the Mediterranean from tropical Africa and the African giant snail Lissachatina fulica. They can cause economic damage on irrigated farmland or in greenhouses by destroying or contaminating crops, making them unsaleable.

Hausdorf’s study compiles records of land snail species introduced to the Western Palearctic region, Europe and the Mediterranean, from other regions after 1492 and established in the wild. In doing so, he observes that the number of alien species has increased steadily since the 19th century, even exponentially from the 1970s onward, and that the introduced species have become more widespread.

Within Europe, alien species generally spread from south to north and from west to east. Thirteen of the 22 species studied were from North America, three from sub-Saharan Africa, two from the Australian region, three probably from the Oriental region, and one from South America.

Even if trade relations and the spread of species can be correlated, Hausdorf believes that the prevailing climate is primarily decisive: “The spread of many of the introduced species, especially the tropical species dispersing in Mediterranean, is probably favored by climate change.”

Bernhard Hausdorf, “Distribution patterns of established alien land snail species in the Western Palaearctic Region”, NeoBiota, Pensoft
https://doi.org/10.3897/neobiota.81.96360

Press release originally published by Leibniz Institute for the Analysis of Biodiversity Change. Republished with permission.

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Can amateurs combat the threat of alien species? Tracking introduced species in the world of citizen science

How citizen scientists documented the spread of an alien mantis across Australia

Guest blog post by Matthew Connors

From the infamous cane toad to the notorious spotted lanternfly, we all know the drastic effects that introduced species can have on both ecosystems and agriculture.

In today’s interconnected world, these alien species are being moved around the globe more frequently than ever before. Hitchhikers and stowaways on ships, planes, and other vehicles can cause irreversible and catastrophic damage to fragile native ecosystems and to us humans, and tens of billions of dollars are spent every year trying to control these invaders.

Spotted lanternfly. Photo by peterlcoffey licensed under CC BY-NC-SA 2.0.

But one of the greatest problems for researchers and government bodies trying to combat these threats is that it can be incredibly difficult to monitor the invaders even when we know they’re here.

So how on earth is anyone supposed to detect when a new species has invaded? Many of these organisms are small, inconspicuous, and difficult to identify, and by the time they’ve been spotted it’s often already too late to act.

What if there was a way to quickly and easily find invasive organisms all over the world? Enter the world of Citizen Science, where anybody and everybody can produce important scientific data without even leaving their backyard. Just by taking a photograph of an organism and uploading it to a citizen science platform like iNaturalist or QuestaGame, amateurs and enthusiasts can provide scientists with invaluable records from across the globe.

A screenshot from the iNaturalist homepage, captured on July 7, 2022.

Back in 2015, when amateur naturalist Adam Edmonds spotted an unusual praying mantis in his garden, he took a photo and posted it to the Australian citizen science platform BowerBird. When even the local experts didn’t recognise it, a specimen was sent off to mantis specialist Graham Milledge. He confirmed that it was a newly introduced species – the South African Mantis (Miomantis caffra).

Miomantis caffra, an adult female from Victoria, Australia. Photo by Adam Edmonds

Since then, this alien mantis has spread across Australia from Sydney to Perth. And every step of the way, citizen scientists have been there to document its spread.

Last month, all of these citizen science records were compiled by entomologist Matthew Connors of James Cook University (Queensland, Australia) into the first comprehensive report of the mantis’s presence in Australia. Understanding where the species has spread and what impacts it has had on native species is crucial to managing and controlling it.

The introduced South African Mantis (*Miomantis caffra*) preys on a native Harlequin Bug (*Dindymus versicolor*) in Geelong, Australia. Photo by Kelly Clitheroe

The research found that the South African Mantis has spread through suburban habitats in three Australian states (Victoria, New South Wales, and Western Australia) and one offshore territory (Norfolk Island). It probably arrived in these regions as egg cases attached to plants and equipment, and it can now be found in high numbers, especially during late summer and early autumn. Despite this, it appears to be highly localised and has only been recorded in suburbia, and furthermore there has not been any noticeable impact on native species.

Miomantis caffra, egg case (ootheca) from Victoria, Australia. Photo by Ken Walker

None of this research would have been possible without citizen scientists – the dedicated community of enthusiasts and amateurs who share their finds with researchers online. Photographs from citizen science platforms and social media sites have been instrumental in showing just how far the South African Mantis has spread. In fact, more than 90% of the records of the species come from citizen scientists, and without them we would barely know anything.

These days, more and more researchers are realising just how useful citizen science can be. As well as tracking introduced species, citizen scientists have rediscovered rare creatures, documented never-before-seen behaviours, and even discovered completely new species.

Miomantis caffra, an adult female from Victoria, Australia. Photo by Matthew Connors

This latest research, published in the Journal of Orthoptera Research, is among a handful of recent studies that have gone a step further though – instead of just being a source of data, the citizen scientists were invited to take part in the entire research process, from data collection all the way through to publishing. After all, they did all of the fieldwork!

Research like this is proof that anyone can be a citizen scientist in today’s day and age – so what are you waiting for?

Research article: Connors MG, Chen H, Li H, Edmonds A, Smith KA, Gell C, Clitheroe K, Miller IM, Walker KL, Nunn JS, Nguyen L, Quinane LN, Andreoli CM, Galea JA, Quan B, Sandiford K, Wallis B, Anderson ML, Canziani EV, Craven J, Hakim RRC, Lowther R, Maneylaws C, Menz BA, Newman J, Perkins HD, Smith AR, Webber VH, Wishart D (2022) Citizen scientists track a charismatic carnivore: Mapping the spread and impact of the South African Mantis (Miomantidae, Miomantis caffra) in Australia. Journal of Orthoptera Research 31(1): 69-82. https://doi.org/10.3897/jor.31.79332

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.