Many vertebrate species would have to evolve about 10,000 times faster than they have in the past to adapt to the rapid climate change expected in the next 100 years, a study led by a University of Arizona ecologist has found. Scientists analyzed¹ how quickly species adapted to different climates in the past, using data from 540 living species from all major groups of terrestrial vertebrates, including amphibians², reptiles³, birds and mammals. They then compared their rates of evolution to rates of climate change projected for the end of this century. This is the first study to compare past rates of adaption to future rates of climate change.

 

The results, published online in the journal Ecology Letters, show that terrestrial vertebrate species appear to evolve too slowly to be able to adapt to the dramatically warmer climate expected by 2100. The researchers suggested that many species may face extinction⁴ if they are unable to move or acclimate⁵.

 

"Every species has a climatic niche⁶ which is the set of temperature and precipitation conditions in the area where it lives and where it can survive," explained John J. Wiens, a professor in UA's department of ecology and evolutionary⁷ biology in the College of Science. "For example, some species are found only in tropical areas, some only in cooler temperate⁸ areas, some live high in the mountains, and some live in the deserts."

 

Wiens conducted the research together with Ignacio Quintero, a postgraduate⁹ research assistant at Yale University.

 

"We found that on average, species usually adapt to different climatic conditions at a rate of only by about 1 degree Celsius¹⁰ per million years," Wiens explained. "But if global temperatures are going to rise by about 4 degrees over the next hundred years as predicted by the Intergovernmental Panel of Climate Change, that is where you get a huge difference in rates. What that suggests overall is that simply evolving to match these conditions may not be an option for many species."

 

For their analysis, Quintero and Wiens studied phylogenies -- essentially¹¹ evolutionary family trees showing how species are related to each other -- based on genetic¹² data. These trees reveal how long ago species split from each other. The sampling covered 17 families representing the major living groups of terrestrial vertebrates, including frogs, salamanders（蝾螈）, lizards¹³, snakes, crocodilians, birds and mammals.

 

They then combined these evolutionary trees with data on the climatic niche of each species to estimate how quickly climatic niches¹⁴ evolve among species, using climatic data such as annual mean temperature and annual precipitation（年降水量） as well as high and low extremes.

 

"Basically, we figured out how much species changed in their climatic niche on a given branch, and if we know how old a species is, we can estimate how quickly the climatic niche changes over time," Wiens explained. "For most sister species, we found that they evolved to live in habitats with an average temperature difference of only about 1 or 2 degrees Celsius over the course of one to a few million years."

 

"We then compared the rates of change over time in the past to projections¹⁵ for what climatic conditions are going to be like in 2100 and looked at how different these rates are. If the rates were similar, it would suggest there is a potential for species to evolve quickly enough to be able to survive, but in most cases, we found those rates to be different by about 10,000-fold or more," he said.

 

"According to our data, almost all groups have at least some species that are potentially endangered, particularly tropical species."

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