Queen’s: Tropical amphibians evolving resistance to world’s deadliest wildlife disease, study finds

A lethal fungal pandemic once blamed for driving amphibians towards extinction may now be losing its grip in tropical regions, according to a major new global study led by Queen’s University Belfast.

The research suggests that many tropical amphibian species have evolved resistance to chytridiomycosis – the most destructive wildlife disease ever recorded – raising cautious optimism that some populations may be stabilising or even beginning to recover.

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has been responsible for catastrophic global declines in frogs, toads, newts and salamanders. The disease has long been regarded as the dominant driver behind what scientists describe as the most severe biodiversity losses seen in any group of vertebrates.

However, the new study, published in the world-leading journal Global Change Biology, challenges the assumption that the disease continues to affect all amphibians equally across the globe.

By comparing historical datasets with more recent figures, researchers examined infection status across thousands of amphibian species in both tropical and colder regions.

The findings reveal stark regional differences in how the panzootic – a disease outbreak affecting animals on a global scale – is now unfolding.

Dr Daniel Pincheira-Donoso, from the School of Biological Sciences at Queen’s University Belfast and principal investigator on the project, said the scale of previous research had created a unique opportunity to reassess the true impact of the disease.

“The idea that this infectious disease has been a dominant cause of the rapid loss of amphibian biodiversity has become a form of paradigm amongst the scientific community to produce volumes of data from thousands of species on a global scale.

“This collective effort created an opportunity for us to gather a comprehensive database spanning the global diversity of amphibian species, including the threatened and non-threatened, and all the thousands of species in which the presence of the disease has been tested.

“We now know that the role of this infectious disease in the extinction of amphibians is not exactly as we thought, with tropical species getting over the panzootic, while these panzootic effects are still ongoing in amphibians from colder climates.”

The research indicates that in many tropical areas – once the epicentre of devastation – the most vulnerable species may already have been lost, while others have survived by developing tolerance or resistance to the fungus. This raises the possibility that some populations are now able to coexist with Bd, rather than continuing on a trajectory towards extinction.

In contrast, amphibians in colder regions such as Europe appear to be facing a worsening situation.

Dr Pincheira-Donoso suggests climate plays a critical role in shaping how the disease spreads and how species respond to it.

“An explanation is that the seasonality of colder climates added to the low density of amphibians in these regions may have acted as ‘natural lockdowns’ and ‘social distance’ effects that have made the impact of the pandemic slower, slowing down the evolution of their resistance.”

The study highlights clear region-specific and time-specific patterns, with tropical amphibians no longer experiencing declines of the same intensity, while non-tropical species continue to decline.

Luke Goodyear, a PhD researcher from the School of Biological Sciences at Queen’s who led the study, said the findings offer both hope and urgency.

“This new research is very exciting as it shows two different ways this disease has affected amphibians. We see early signs of possible stabilisation in environments around the equator, which were initially hit very hard by the disease.

“Although many species are still at risk in these regions, it seems that the peak of devastation might be behind us.

“Then in colder climates, like Europe, we see the opposite. This is the first research to show the increasing impact on these amphibian species at this scale. Hopefully this can speed up conservation action while there is still time to prevent the mass declines we saw in tropical climates.”

Conservationists say the findings underline the importance of region-specific strategies, with urgent intervention still needed in temperate zones to prevent further losses.

The paper can be read in full here.