科学美国人60秒 SSS Cold Snap Shapes Lizard Survivors

Cold Snap Shapes Lizard 1 Survivors 2

南方寒潮中的幸存者后来都怎样了

In January 2014, an epic 3 cold wave swept across the southeast—a "snowpocalypse" so severe that thousands of drivers in Atlanta abandoned their cars on icy highways and Interstates.

2014年1月，一场史诗般的寒潮席卷了整个东南地区——严重到堪称“末日暴雪”，以至于亚特兰大数千名司机在结冰的高速公路和州际公路上弃车而去。

"And I'm from the south, I was raised in South Carolina, and I can tell you that in the South we do not do cold—at all."

“我来自南方，我是在南卡罗来纳长大的，我可以告诉你，在南方我们从来没冷过——一点都没有。”

\Shane Campbell-Staton was watching it all unfold from Harvard, where he was getting his PhD. He'd just wrapped up his last field season in Texas, studying the green anole lizard. And as he was scanning photos of the storm, he came across something unexpected: a photo that included his research subject.

肖恩·坎贝尔·斯塔顿在哈佛看到了这些资料，他也是在这里拿到了博士学位。肖恩刚刚结束了在德克萨斯州野外对绿色变色龙蜥蜴的研究课题。他在扫描那次风暴的照片时，偶然发现了意想不到的状况：一张照片中竟然出现了他的研究课题。

"There was this one picture of a green anole that was upside down, dead in the snow. And it was sort of a Eureka moment. And I thought to myself, well maybe I should go back out and see if these populations I'd been studying, if they showed any sort of response to this pretty extreme weather event in the south."

“有一张照片中出现了一只颠倒的、死在雪地里的绿变色蜥。那一刻有种终于找到某物想欢呼的感觉。我当时想，也许我应该回去看看我一直在研究的这个群体，看看它们对这次南方的极端天气事件是否有何反应。”

And so that's what he did. Because here's the bit of serendipity 4: he'd actually been studying the cold tolerance 5 of different populations of these lizards 6. And the cold snap had just delivered the perfect experiment—a chance to see natural selection in action.

然后他就那样做了。这次研究有点意外收获的意思：实际上，他一直在研究这种蜥蜴中不同种群的耐寒性。而这次寒流恰巧做了一次完美的实验——一个看到自然选择发生作用的机会。

"So I went back in April right after these winter storms had subsided 7. And I noticed that in the south, the southernmost population, the survivors of the storm were able to maintain function at significantly colder temperatures than the population before the storm. And this ability to maintain function at colder temperatures is something we typically see much farther north."

“因此，4月份当这些冬季风暴消退之后，我就立刻回到那里去了。我注意到，在南部最南端的种群中，与风暴来临之前相比，经历过风暴的幸存者能够在温度显著降低的环境中维持其功能。而这种在更冷的温度下保持功能的能力，我们通常只在更偏北的种群中见到。”

He did genetic 9 analyses too: and found that the genes 10 switched on in the surviving southern lizards overlapped 11 with genes more typically turned on in their cold-hardy northern cousins. And the survivors also carried variations in their DNA 12 that more closely matched northern lizards. So three things: cold tolerance, gene 8 expression, and even the gene variants 13 the southerners carried, suggested this winter storm had indeed caused selection on the southern lizards. The analysis is in the journal Science.

他还做了基因分析：他发现，在幸存的南方蜥蜴身上开启的基因与更典型的表现在抗寒能力更强的北方蜥蜴身上的基因一致。而且，幸存的南方蜥蜴还携带了更接近北方蜥蜴基因的基因变异。因此，耐寒性、基因表达、甚至是南方蜥蜴携带的基因变体——这三种表现，表明这场冬季风暴确实导致南方蜥蜴做出了自然选择。这项分析报告发表在《科学》杂志上。

Campbell-Staton, now at the University of Illinois and the University of Montana, is quick to mention that this isn't quite evolution yet. It's just one generation—he hasn't yet seen these traits passed down to another set of lizards. That's his next investigation 14.

目前在伊利诺伊大学和蒙大拿大学的坎贝尔·斯塔顿很快就指出，这还不算是进化。这种变化只表现在一代蜥蜴身上——他还没有看到这些特征被传到另一代蜥蜴身上。而这将是他的下一个研究项目。

As for whether this is a good thing, the fact that some lizards were able to summon the ability to survive cold? "The answer is both yes and no potentially." Yes, because if another cold wave rolls through, the surviving southern population will be better prepared—more cold-tolerant.

至于一些蜥蜴拥有了能够在寒冷环境中生存下来的能力，这是不是一件好事？“答案既有可能是肯定的，也有可能是否定的。”是的，因为如果再发生一次寒潮侵袭，幸存下来的南方蜥蜴将做好更好的防御——因为耐寒性更强了。

But: "We know that selection comes at a cost. Which is death. So the individuals that died during this event may have had genetic variants that would have allowed them to survive a heat wave, or a drought, or some other extreme event. And now those lineages are essentially 15 gone."

但是:“我们知道自然选择是要付出代价的，即死亡。因此，在这次事件中死亡的那些个体可能携带一些能使它们在热浪、干旱或其他极端事件中生存下来的遗传变体。而现在这些血统基本上消失了。”

The long term forecast for the 21st century includes more of these extreme events—and more severe ones at that. So species that lose their genetic Swiss army knife of adaptive tools may, again, be left out in the cold.

对21世纪的长期预测中包含了更多的这些极端事件——而且其中还有更为严重的。因此，那些失去了基因中的“瑞士军刀”自适应工具的物种，可能会再次在寒冷的环境中被抛弃。