气候变化使蝾螈体型变小

Wild salamanders（蝾螈） living in some of North America's best salamander habitat are getting smaller as their surroundings get warmer and drier, forcing them to burn more energy in a changing climate. That's the key finding of a new study, published March 25 in the journal Global Change Biology, that examined museum specimens¹ caught in the Appalachian Mountains from 1957 to 2007 and wild salamanders measured at the same sites in 2011-2012. The salamanders studied from 1980 onward² were, on average, 8% smaller than their counterparts from earlier decades. The changes were most marked in the Southern Appalachians and at low elevations⁴ -- settings where detailed⁵ weather records showed the climate has warmed and dried out most.

 

Scientists have predicted that some animals will get smaller in response to climate change, and this is strongest confirmation⁶ of that prediction.

 

"This is one of the largest and fastest rates of change ever recorded in any animal," said Karen R. Lips, an associate professor of biology at the University of Maryland and the study's senior author. "We don't know exactly how or why it's happening, but our data show it is clearly correlated with climate change." And it's happening at a time when salamanders and other amphibians⁸（两栖动物） are in distress⁹, with some species going extinct and others dwindling¹⁰ in number.

 

"We don't know if this is a genetic¹¹ change or a sign that the animals are flexible enough to adjust to new conditions," Lips said. "If these animals are adjusting, it gives us hope that some species are going to be able to keep up with climate change."

 

The study was prompted by the work of University of Maryland Prof. Emeritus¹² Richard Highton, who began collecting salamanders in the Appalachian Mountains in 1957. The geologically ancient mountain range's moist forests and long evolutionary¹³ history make it a global hot spot for a variety of salamander species. Highton collected hundreds of thousands of salamanders, now preserved in jars at the Smithsonian Institution's Museum Service Center in Suitland, MD.

 

But Highton's records show a mysterious decline in the region's salamander populations beginning in the 1980s. Lips, an amphibian⁷ expert, saw a similar decline in the frogs she studied in Central America, and tracked it to a lethal¹⁴ fungal disease. She decided¹⁵ to see whether disease might explain the salamander declines in the Appalachians.

 

Between summer 2011 and spring 2012, Lips and her students caught, measured and took DNA¹⁶ samples from wild salamanders at 78 of Highton's collecting sites in Maryland, Virginia, West Virginia, Tennessee and North Carolina. Using relatively¹⁷ new techniques for analyzing¹⁸ DNA from preserved specimens, the researchers tested some of Highton's salamanders for disease.

 

Lips found virtually no fungal disease in the museum specimens or the living animals. But when she compared size measurements of the older specimens with today's wild salamanders, the differences were striking.

 

Between 1957 and 2012, six salamander species got significantly smaller, while only one got slightly larger. On average, each generation was one percent smaller than its parents' generation, the researchers found.

 

The researchers compared changes in body size to the animals' location and their sites' elevation³, temperature and rainfall. They found the salamanders shrank the most at southerly sites, where temperatures rose and rainfall decreased over the 55-year study.

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