Climate Change Alters Tree Frog Evolution
October 26, 2012

Evolution Is Changing For Panama Tree Frogs Due To Climate Change

April Flowers for - Your Universe Online

Though most of the over 6,000 species of frogs lay their eggs in water, many tropical frogs must lay their eggs out of water to protect them from aquatic predators, such as tadpoles and fish. The problem with this is that it increases the risk of the eggs drying out.

A post-doctoral fellow at the Smithsonian Tropical Research Institute, Justin Touchon, recently discovered that climate change in Panama may be altering the course of evolution for these frogs.

Touchon analyzed long-term rainfall data collected by the Panama Canal Authority to reveal that rainfall patterns are changing, just as climate-change models have predicted.

"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 pantless tree frog, Dendropsophus ebraccatus, has eggs that are extremely susceptible to drying out. They are so sensitive that the embryos die within a day when there is no rain. Breeding is triggered by heavy rains. As the changing climate makes the storms sporadic, the chance of rain within a day of eggs being laid decreases, and so does egg survival.

The advantage of laying eggs out of water has decreased as weather patterns change, not only for the pantless tree frog but for many other species as well.

"Pantless tree frogs 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."

Touchon's findings are published in The American Naturalist online.