在新墨西哥州沙漠中对几十只蜥蜴的最新研究表明，目前，在全球变暖背景下，用于预测物种生存的模型可能偏离了目标。

由于地球变暖的速度比这些种群适应的速度要快，因此，世界上40%的蜥蜴种群预计会在2080年灭绝。

但是，发表在美国国家科学院会议上的最新研究表明，想要做出准确的预测，这些模型必须包括更多的数据，遮阳地在动物的栖息地是如何分布的。

根据华盛顿大学生物学名誉教授雷蒙德 休伊的介绍，“这是一项突破性的研究”。“研究气候变暖的科学家们需要评估阳光和阴凉面积的空间分布，而不能仅仅计算一个区域阳光或背阴面积的比例。”

“坦率地说，这给我们的研究工作增加了难度，但也更有趣。”

即使体温发生很小的变化，也能显著影响生物体的状态。比如，当一个人的体温上升1到2度。爬行动物，包括蜥蜴，通过在它们栖息地的温暖和凉爽区域之间移动，来调节自己的体温。

不仅仅是温暖和凉爽区域的相对比例会影响蜥蜴如何调节它的体温，休伊说，也包括它们在空间上是如何分布的。

在本研究中，如果蜥蜴所处之地有很多小块的阴凉地，那么它们就能更加有效地调节体温，在这种地形条件下，它们能够很快爬到阴凉处，如果是一片开阔地，有一大片阴凉地，情况就不一样了。

“取决于环境的复杂性，以前估计的灭绝率或者太高，或者不够高，”麦克 西尔斯说，他是克莱姆森大学生物学副教授、该研究的主要作者。

“真正令人担心的是，以往的研究低估了灭绝的风险，” 亚利桑那州立大学教授，研究论文合著者Mike Angilletta说。

“大多数模型假设动物在它的环境中可以在任意时间抵达任意地点，却没有考虑动物要花费多少能量来调节它的体温。动物要移动和搜索的阴凉地，当阴凉处相距甚远时，它们就很难为自己降温”Angilletta说。

西尔斯花了20年的时间研究蜥蜴。他说爬行动物特别适合气候变化的研究，因为“它们像移动的小小恒温器。”

休伊说，让这项研究最引人注目的，是它一次解决了三个问题。

“它首次开发了高复杂性的计算机模拟模型，模拟复杂热环境下动物的运动模式，”休伊说。“在该研究领域，它加入了大规模动物实际运动模式实验。最后，它显示出气候变暖——在现实热环境中——比目前所预测的有着更严重的影响。”

当西尔斯首次质疑目前的模型时，他建立了一个计算机模拟来检验他们的假设。数字蜥蜴遵循调节体温最有效的算法。在虚拟环境中，西尔斯的数字蜥蜴会告诉他，当阴凉地是聚集在一起或分散开的时候，它们要花费多少能量来调节体温。

在虚拟环境中，当阴凉地是小块分散的时候，数字蜥蜴能够更加有效地调节体温：它们需要很少的能量就能从一块阴凉地移动到另一块。在一个地点，当阴凉地是孤立存在的，蜥蜴不得不移动到更远的地方来寻找食物，而这需要更多的能量。

西尔斯，Angilletta和来自另外两所大学的同事们，用真蜥蜴验证他们的计算机模型，地点是新墨西哥州阿尔伯克基以南80英里，新墨西哥大学Sevilleta场站附近。

在过去两个夏天，研究人员和他们的学生在九个场地设了围栏，每一个场地是20*20平方米。为了模拟仿真的阴凉地，他们在每一个场地上用了相同大小的舞台遮阳布，但是遮阳布的分布是不同的，有的是一大片遮阳布，4块阴凉地或16个小的阴凉地。

在每个环境中，每一组蜥蜴呆两天时间，研究人员用微型的植入式传感器对它们的体温进行监测。

在一大片阴凉地的场地，蜥蜴比四个阴凉地的场地体温变化超过12%，比16个阴凉地的场地，体温变化超过10%。因此，更多的阴凉地意味着能够更加精细地调节温度。

这一结果与西尔斯的计算机模型相符。在模拟中，一大片阴凉地与4块或16块阴凉地对比，数字蜥蜴的体温变化是9%。

“作为一个年轻人，我学到了热资源的空间分布非常重要，”休伊说。“西尔斯和他的同事们将这个研究课题上升到了新的复杂水平上，显示出遮阴地分布如何影响蜥蜴调节体温的能力，以及理解这种分布对于预测气候变暖的生物反应非常关键。”

这项研究证实了西尔斯的预感，全球气温并不足以预测物种的生存。

“如果我们真的想要了解生物种群如何应对气候变化，我们不能仅仅用一个简单、保守的方法，”西尔斯说。“我们需要认真思考比现有研究更加精细的方法。”

“英文原文”

Lizard study finds global warming data not enough to predict animal extinction

Current models used to predict the survival of species in a warming world might be off target, according to new research that enlisted the help of dozens of spiny lizards in the New Mexico desert.

Almost 40 percent of the world's populations of lizards are expected to become extinct by 2080, because the earth is warming faster than these populations can adapt.

But the new study, published in Proceedings of the National Academy of Science, shows that, to make accurate predictions, these models must include much more data about how shade is distributed in an animal's habitat.

"This is a breakthrough paper," according to Raymond Huey, a professor emeritus of biology at the University of Washington. "Scientists studying climate warming will now be forced to evaluate the spatial distribution of sunny-shady patches, and not just compute the fraction of an area that is sunny or shady.

"Frankly, that makes our research lives much harder, but also much more interesting."

Even a small change in body temperature can dramatically affect an organism's well-being, like when a person's temperature rises one or two degrees. Reptiles, including lizards, regulate their body temperatures by moving between warm and cool areas within their home ranges.

It isn't just the relative proportion of warm and cool areas that affects how well a lizard can regulate its temperatures, Huey said, but also how they are distributed in space.

The spiny lizards in the study regulated their temperatures much more efficiently when they had many small patches of shade, which they could easily reach to cool off, instead one large clump of shade in a wide-open space.

"Depending on the complexity of the environment, previous estimates of extinction may be too high or they might not be high enough," said Mike Sears, an associate professor of biology at Clemson University and the lead author of the study.

"The real fear is that previous research has underestimated the risk of extinction," said Mike Angilletta, a professor at Arizona State University and coauthor of the study.

"Most models assume that an animal can be anywhere in its environment at any time, which doesn't account for how much energy an animal spends to regulate its temperature. Animals have to move and search for shade, which makes cooling down more difficult when patches of shade are far apart," Angilletta said.

Sears has spent 20 years studying lizards. He says the reptiles are especially suited for climate change studies because "they're like little thermostats running around."

What makes this study remarkable, Huey said, is that it tackles three issues at once.

"It develops original and highly sophisticated computers simulations of animal movement patterns in complex thermal environments," Huey said. "It adds large-scale experiments of real animal movement patterns in the field. Finally, it shows that climate warming—in realistic thermal landscapes—may have more serious effects than predicted so far."

When Sears first questioned the current models, he built a computer simulation to test their assumptions. Digital lizards followed algorithms that regulated body temperatures most efficiently. In the virtual environment, Sears' digital lizards told him how much energy they spent on regulating their body temperatures when shade was either clumped together or spaced apart.

When shade was dispersed throughout a simulated environment, the digital lizards were able to regulate their temperatures more efficiently: they required less energy to move from patch to patch. When shade was isolated to one location, the lizards had to move farther away to hunt for food, which required more energy.

Sears, Angilletta and colleagues from two other universities tested their computer model with real lizards near the University of New Mexico's Sevilleta Field Station, about 80 miles south of Albuquerque, New Mexico.

Over two summers, the researchers and their students fenced in nine arenas, each 20 by 20 meters square. To mimic the shade of the simulations, they stretched equal areas of shade cloth over each arena, but arranged the cloth differently—one big clump of shade, four medium-sized patches of shade or 16 small patches.

Each group of lizards spent two days in each environment, and their body temperatures were monitored through tiny, surgically implanted sensors.

When the lizards were in the arena with one large clump of shade, their temperatures varied 12 percent more than when they were in the arena with four patches of shade, and 10 percent more than when they were in the arena with 16 patches of shade. Thus, more patches mean more careful thermoregulation.

The results corresponded to Sears' computer model. In the simulations, digital lizards experienced nine percent more variation in body temperature when shade was provided in one clump compared to either four patches or 16 patches.

"As a young lad, I leaned that spatial distribution of thermal resources mattered," Huey said. "But Sears and colleagues take this theme to a general and sophisticated new level, and show how the distribution of shade patches affects the ability of lizards to use behavior to regulate their body temperatures, and also why an understanding of that distribution will be critical to predicting biological responses to climate warming."

The research confirmed Sears' hunch, that global temperatures aren't sufficient for predicting how well species survive.

"If we really want to understand how populations of organisms will respond to climate change, we can't use a simple, back-of-the-envelope method," Sears said. "We need to think on a finer scale than we have been."

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