英语语法分析

North and South American species migrating across the Isthmus now came into competition with each other.

北美和南美的物种迁徙穿过地峡，现在开始互相竞争。

Second, it appears that closely related populations of fishes on both sides of the isthmus are starting to genetically diverge from each other.

其次，地峡两侧紧密相关的鱼类种群似乎开始在基因上彼此分化。

While previously the gap between the continents had allowed a free flow of water, now the isthmus presented a barrier that divided the Atlantic Ocean from the Pacific Ocean.

以前，大陆之间的鸿沟允许水自由流动；而现在地峡形成了一道屏障，把大西洋和太平洋分隔开来。