时差N小时 种群动态进化（在线收听）

Until recently, many ecologists didn't study the effect of evolution on population dynamics because evolution is much slower than the predator-prey cycle.

直到最近，许多生态学家都没有研究种群动态进化所带来的影响，因为进化的速度远远慢于捕食的周期。

But a study suggests that adaptive evolution might actually play a role in the dynamics ofthe predator-prey relationship.

但是研究表明，适应性进化可能影响着掠食者与被掠食者之间的动态。

Cornell University biologists studied the population dynamics of green algae and rotifers, the microscopic aquatic animals that feed on them.

康乃尔大学的生物学家研究了以绿藻为食的轮虫的种群动态。

They expected that the rotifers would eat the algae and multiply until the algae population crashed.

他们预测，轮虫将会吃掉绿藻并繁衍后代直到绿藻的种群锐减。

This would then cause the rotifer population to crash, which would allowthe algae population to recover, and the whole cycle to begin again.

由于绿藻的减少，轮虫的种群也会锐减，这时绿藻种群便开始恢复，整个循环周期便又开始了。

What they observed, however, was that there was some lag between the time the algae population reached a certain density and the time the rotifer population began its recovery.

但是他们观察到在绿藻种群到达一定的密度之后，轮虫种群并没有立刻开始恢复。

Why? And how does evolution fit into all this?

为什么呢？进化过程是如何与之一致的呢？

Well, it turns that some algal cells are resistant to digestion, although this resistance comes at a cost: they reproduce more slowly.

实际上，有些藻类细胞会对消化产生抵抗性。尽管这些抵抗也是有代价的：它们的繁殖更加缓慢。

As the more dominant, non-resistant strains of algae crashed, the resistant algal cells began cloning themselves more rapidly, and this temporarily stabilized the algae population.

由于处于优势，不抗消化的绿藻品种数量减少，抗消化的绿藻细胞开始更加快速的繁殖，这就暂时稳定了绿藻种群。

In the meantime, the rotifer population crashed because the rotifers had less to eat,allowing the non-resistant strains of algae to recover.

同时，轮虫种群随着它们食物的减少而减少，这就让不抗消化的绿藻品种开始恢复。

Once the non-resistant algae became common again, the rotifer population increased, completing the cycle.

一旦不抗消化的绿藻又变得普遍了，轮虫种群就开始增长，完成整个循环周期。

So basically, adaptive evolution enabled the algae population to reestablish itself by delaying the time it took the predator population to recover.

因此，适应性进化使得绿藻种群能够通过拖延捕食者种群恢复的时间来重建自己。

Understanding the effects of adaptive evolution may help scientists to better understand the behavior of drug-resistant bacteria and outbreaks of disease.

对适应性进化影响的了解将会帮助科学家更好的明白抗药菌的行为以及疾病的爆发。