Tropical lowland frogs at greater risk from climate warming than high-elevation species, study shows

April 7, 2017 by Jim Erickson, University of Michigan
Bryophryne hanssaueri is one of the 22 species included in the Peruvian frog study. Individuals of this species have a bright orange throat and belly. Adults typically range in size from 0.47 to 1.13 inches (1.20 - 2.87 centimeters) in length. These frogs live under mosses and leaf litter in the high-elevation cloud forest between 10,480 and 11,250 feet, just below the treeline. Like other Bryophryne species, females attend clutches of direct-developing embryos until they hatch into tiny froglets. Credit: Alessandro Catenazzi

A new study of Peruvian frogs living at a wide variety of elevations—from the Amazon floodplain to high Andes peaks—lends support to the idea that lowland amphibians are at higher risk from future climate warming.

That's because the lowland creatures already live near the maximum temperatures they can tolerate, while high-elevation amphibians might be more buffered from increased temperatures, according to a study by University of Michigan ecologist Rudolf von May and his colleagues published online April 6 in the journal Ecology and Evolution.

Previous studies have suggested that lowland reptiles and amphibians are especially vulnerable to climate warming. But in most cases, those conclusions were based on computer modeling work that incorporated a limited amount of field data.

"Understanding how species respond to climatic variation is critical for conserving species in future climatic conditions. Yet for most groups of organisms distributed in tropical areas, data about species' critical thermal limits are limited," said von May, a postdoctoral researcher in the U-M Department of Ecology and Evolutionary Biology.

"I think the contribution of our study is that it focuses on a group of closely related distributed along a single montane gradient and that it includes empirical data on species' tolerance to heat and cold, as well as air temperatures measured along the same gradient."

In the process of conducting the study, which involved more than two years of fieldwork, von May and his colleagues identified three previously unknown species. Those newly discovered species will be described separately in a series of journal articles.

The elevational-gradient study focused on the thermal ecology and evolution of 22 species of land-breeding frogs, which are also known as terrestrial-breeding frogs, in southern Peru's Manu National Park and surrounding areas. Sampled elevations ranged from the Amazon River floodplain, at 820 feet above sea level, to 12,000-foot Andes Mountains peaks.

The region in and around Manu National Park is known for long-held records of biodiversity including more than 1,000 species of birds—about 10 percent of the world's bird species—and more than 1,200 species of butterflies. In addition, the park contains an estimated 2.2 percent of the world's amphibians and 1.5 percent of its reptiles.

While most frogs lay eggs in water, terrestrial-breeding frogs use a specialized reproductive mode called direct development: A clutch of embryos hatch directly into froglets; there are no free-living tadpoles. Terrestrial-breeding frogs form a diverse group that can exploit a wide variety of habitats, as long as those locations contain sufficient moisture.

In the study, the researchers looked at how closely related frog species differ in their elevational distribution and their tolerance to heat and cold in a region of the tropical Andes where temperature increase is predicted to be detrimental for most species.

"These measurements were taken in order to determine whether tropical frogs could take the heat—or cold—predicted for tropical regions as a result of climate change," von May said.

The researchers found that the frogs' tolerance to heat varied from 77 degrees Fahrenheit to 95 degrees and that, as expected, highland species tolerated much lower temperatures than lowland species.

Frogs living in high-elevation grasslands tolerated near-freezing temperatures, which they experience during the dry season, as well as moderately high temperatures, which they may experience during sunny days.

When considering the temperature of the microhabitats in which the frogs live, the results suggest tropical lowland live close to their thermal limit. Amphibians living at high elevation might be more buffered from future increases because the highest temperatures they can tolerate are farther away from the maximum temperatures that they regularly experience in the wild.

Von May is the first author of the Ecology and Evolution paper, "Divergence of thermal physiological traits in terrestrial breeding frogs along a tropical elevational gradient."

Explore further: Tiny frogs face a troubled future in New Guinea's tropical mountains

More information: Rudolf von May et al. Divergence of thermal physiological traits in terrestrial breeding frogs along a tropical elevational gradient, Ecology and Evolution (2017). DOI: 10.1002/ece3.2929

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1 / 5 (3) Apr 07, 2017
I wonder, did the frogs have the same issues during the 400 years (CE 850 - CE 1250) it was warm enough to grow vineyard grapes in Newfoundland, Nova Scotia, Scotland and Scandinavia? When it was warm enough for Barley, Wheat and Dairy Cattle farming on Greenland? During the longer growing seasons concurrently noted in China?

Well, did they?
1 / 5 (2) Apr 08, 2017
More scientists in bed with politicians who want to use "climate change" supposedly caused by man, to pick our pockets. Note they didn't they disclose their funding sources in this report, but being from a government funded university they probably didn't want to tell readers they were picking their pockets either.
5 / 5 (1) Apr 08, 2017
Note they didn't they disclose their funding sources in this report, but being from a government funded university they probably didn't want to tell readers they were picking their pockets either.

Ummm, they did identify the funding - it came from a combination of public and private funds. The paper is freely available, so it's a failure on your part that you didn't see it. As you've indicated, you didn't read the paper and your comment is just a knee jerk political response on your part. There doesn't seem to be anything controversial about the paper, other than the fact that it disagrees with your personal political beliefs. What part of the empirical data do you disagree with?

Since you didn't read the paper, it doesn't appear that you're interested in science at all - why do you come here? Just to spout your political beliefs?

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