Frogs around the world are dying at an unprecedented rate, and researchers from the University of Central Florida (UCF) plan on figuring out why.
The latest study, led by UCF biologist Anna Savage, suggests that natural selection coupled with other evolutionary forces has largely changed the immune genes in lowland leopard frog populations, helping them survive a deadly fungus that's killing off many other species worldwide.
"If there is a massive, sudden change in frog populations, then maybe something in the environment is changing in a broad way that could also impact us," Savage explained. "Fungal pathogens are on the rise, not just Bd (the chytrid fungus, Batrachochytrium dendrobatidis) in frogs, but there is white nose syndrome in bats, snake fungal disease, and there has been an increase in human fungal pathogens across the world. So you could argue that it's a hallmark of a broad global process such as climate change."
The focus of the recent study was to learn more about how the frog genome interacts with environmental variables like temperatures, which could lead to either susceptibility or resistance to the Bd fungus.
"It affects the amphibian's outermost skin layers where keratin is found, so much so that it doesn't allow amphibians to breathe, hydrate or thermoregulate correctly," Savage added. "Our research has found that some lowland leopard frog populations have evolved to tolerate infection due to variation in immune system genes than enable some individuals to survive."
There are believed to be 7,000 amphibian species in the world, occupying every continent except for Antarctica. In the UCF arboretum alone, there are 10 frog species, including leopard frogs, pine frogs, cricket frogs and the invasive Cuban tree frog.
What's more is Bd has been linked to the decline and even extinction of several of these species, so researchers examined what role frog immune genes play when an individual comes into contact with the fungus.
"We are doing field-based work in Florida to establish a pattern, because we know the pathogen is here and we are trying to establish if there are seasonal patterns of infection and trying to figure out which species are most impacted and should be focused on in future population genetic studies," Savage concluded.
Their findings were published in the March 23 issue of the Proceedings of the Royal Society B.
