What a salamander virus can tell us about the future of biodiversity in a changing climate

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A new project by two NAU scientists aims to predict the future, specifically the future of different amphibian species in the face of an unpredictable environment.

Principal investigator Joseph Mihaljevic, assistant professor in the School of Informatics, Computing, and Cyber ​​Systems who studies the ecology of infectious diseases, and co-PI Jason Ladner, assistant professor in the Pathogen and Microbiome Institute who studies epidemiology genomics, received an $844,000 grant from the National Science Foundation to study ectotherms – a type of cold-blooded organism that includes amphibians, fish, reptiles and insects. Their project will create better, more predictive models to help scientists understand how climate change and infectious diseases are likely to interact in the future to impact the health of wildlife and predict how climate and disease affect these species, including those threatened with extinction.

Ectotherms play a variety of diverse roles in the ecosystem; amphibians eat many insects considered pests and are food sources for snakes, fish, birds and other animals. Because they have both water and land life stages, they are an important part of the food web of multiple ecosystems.

“Our ultimate goal is to better understand and better predict how climate change interacts with infectious diseases to determine whether certain species might be at higher or lower risk of extinction, especially for ectothermic species,” Mihaljevic said. “For these types of species, whose body temperature is regulated by the environment, climate determines how well they can cope with infectious diseases, and climate also impacts how these species survive and reproduce. in their habitats. We need better predictive models of when climate and disease are expected to have the greatest combined impacts on these species in the future. This is important for biodiversity conservation, as well as for the agriculture and aquaculture.

The research will focus on ranaviruses, a group of naturally occurring viruses that infect amphibians, and their effects on the tiger salamander population. Mihaljevic called it the “Ebola virus of the amphibian world”; it causes systemic infection and organ failure in salamander larvae, but adults are usually able to mount an effective immune response. Tiger salamanders can live for a decade or more, so even if a virus outbreak decimates a set of offspring, the animals still have many years to reproduce. Historically, this means that the overall salamander population has remained fairly stable.

This is good news for the tiger salamander, but not all amphibians live that long. Many species do not have as many reproductive opportunities, which means their populations are much more susceptible to this and other diseases that evolve unpredictably as the climate changes.

Researchers will study natural populations of salamander larvae in Arizona water bodies. They test for the virus by dabbing the skin of larvae and adults; the virus is released from the skin into the water, so they can detect the virus molecularly on the swabs. They will also monitor when the adults breed and how many eggs they produce and can relate these patterns to rainfall, temperature patterns and other climate indicators.

Using laboratory experiments, they will study how water temperature affects virus transmission and incorporate this knowledge into mathematical models, which will explain how climate influences salamander reproduction and the severity of virus outbreaks. . The next step is to examine the long-term effects on population sizes, simulating what the climate will look like in 20, 30 or 50 years and trying to predict the likelihood that salamander populations will decline over time. What they learn from salamanders will help create better models that can be applied to predict whether other amphibian species are at higher or lower risk of extinction in the future.

This is a critical question to answer when we know the threat of climate change is real, but we don’t know the specific forms that threat will take.

“Emerging infectious diseases are a serious concern for global biodiversity, particularly due to the movement of animals and pathogens through human activity, and future climate change has the potential to exacerbate the impacts of infectious diseases, especially especially for exothermic species that are not able to self-regulate their internal temperature,” Ladner said. “This work is important because it will allow us to link seasonal disease dynamics to temperature variability to understand how infectious disease impacts might be affected by climate change.”

As part of the project, the team will also sequence up to 50 genomes of Ambystoma tigrinum virus (a type of ranavirus) isolated from various wild species, allowing them to explore fundamental questions about how this pathogen survives and circulates in the southwest. .

Mihaljevic and Ladner are also partnered with Greg Dwyer from the University of Chicago and scientists from Arizona Game and Fish. Several undergraduate students and one doctoral student will participate in the research, which builds on the work of master’s students Kelsey Banister and Kathryn Cooney, alumni Diego Olivo and Monica Long, and undergraduate students Braden Spencer and Zane Ondovcik. Olivo and Spencer’s collaborative project was funded by Urdea, Ondovcik’s current project is funded by the Hooper Undergraduate Research Award. It also builds on efforts funded by a Heritage Grant from Arizona Game & Fish and TRIF.

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