Climate Change May Alter Amphibian Evolution

Last week the Smithsonian Tropical Research Institute published a press release on their website highlighting the findings from a research on the pantless treefrog  (Dendropsophus ebraccatus) that is shifting its reproductive mode in response to climate change in Panama. The pantless treefrog can lay eggs both in water and out of the water with different benefits for both reproductive modes; however when eggs are laid out of the water they are susceptible to drying, so daily rains are necessary. The researched showed that rainfall has become less sporadic and less predictable in the last four decades and this species is opting more for laying eggs in the water because of this. The study shows that climate change is occurring in this region with some significant effects on reliability of rainfall and storms in the wet season and an effect therefore on survival of frog embryos.  Luckily the pantless treefrog is able to switch in its reproductive mode, but other species might not be so lucky.

Pantless tree frog. Credit: Wikipedia

Now follows the press release from the Smithsonian Tropical Research Institute; if you go to the original presss release on the website you will find a short movie on the researcher as well.

Most of the more than 6,000 species of frogs in the world lay their eggs in water. But many tropical frogs lay their eggs out of water. This behavior protects the eggs from aquatic predators, such as fish and tadpoles, but also increases their risk of drying out. Justin Touchon, post-doctoral fellow at the Smithsonian Tropical Research Institute, discovered that climate change in Panama may be altering frogs’ course of evolution.

By analyzing long-term rainfall data collected by the Panama Canal Authority, Touchon discovered that rainfall patterns are changing just as climate-change models predict. “Over the past four decades, rainfall has become more sporadic during the wet season,” said Touchon. “The number of rainy days decreased, and the number of gaps between storms increased.”

The eggs of the pantless treefrog, Dendropsophus ebraccatus, are extremely susceptible to drying. The embryos die within a day when there is no rain. Heavy rains trigger breeding, so as storms become sporadic, the chance of rain within a day of being laid decrease and so does egg survival.

Embryos of he pantless tree frog developing outside the water. Credit: Justin Touchon

As weather patterns have changed, the advantage of laying eggs out of water has decreased, not only for pantless treefrogs but potentially for many species. “Pantless treefrogs can switch between laying eggs in water or on leaves, so they may weather the changes we are seeing in rainfall better than other species that have lost the ability to lay eggs in water,” said Touchon. “Being flexible in where they put their eggs gives them more options and allows them to make decisions in a given habitat that will increase the survival of their offspring.”

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