Researchers have discovered a key link between the global decline of amphibian populations and climate change, according to a study published by Wiley Online. The researchers used the thermal mismatch hypothesis to test species’ interactions between parasites and host amphibians to reveal how those interactions are altered by changing temperatures, then matched those results to global climate data to find a strong correlation suggesting that climate change is a prevailing factor in high amphibian mortality rates.
The thermal mismatch hypothesis is a biological principle that states that host species adapted for warmer or cooler temperatures are more vulnerable to climate change as they become more susceptible to parasitic diseases as temperatures change.
To test the hypothesis, the research team conducted experiments with a critically endangered frog that was bred in captivity in their lab. The Atelopus zeteki prefers cooler temperatures, but despite its endangered status is a relatively hardy species. In a series of experiments, the researchers exposed the frogs to the pathogenic chytrid fungus in various temperature environments. In accordance with the thermal mismatch hypothesis, it was found that mortality rates were highest when the two species were at their greatest temperature mismatch. In this case, high temperatures that supported the fungus had the greatest negative effect on the frogs. At the preferred cooler temperatures, the frogs were not susceptible to the fungus but became increasingly more vulnerable as temperatures increased.
New report – global vertebrate populations (mammals, birds, reptiles, amphibians, fish) declined 60% from 1970-2014 https://t.co/Ptc5sldXGU
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The researchers then conducted a series of experiments related to other hypotheses regarding amphibious decline and found that the strongest correlation was made by the thermal mismatch hypothesis. Only the combination of increased temperatures and infectious disease could account for the rate of global decline of each species of frog in the genus Atelopus, especially for those species that were adapted to cooler environments.
Combining the results of the experiments on the declining host populations with global climate data over time, the researchers discovered a pattern consistent with the hypothesis that the widespread decline and extinction of each species have been driven by an interaction between rising temperatures and infectious disease. Furthermore, species adapted for cool temperatures have been the most susceptible due to the more advantageous warmer environment for parasites, though warm-temperature species also showed a strong susceptibility in cooler temperatures.
The findings account for changes among 598 global populations of 235 amphibian species, creating a remarkable consistency across a wide range of populations and species. Further research will be conducted to test the thermal mismatch hypothesis on other species of various environmental adaptations.