parapatric speciation

例句：

1. 1. Thetwo species of birds are separated by a narrow river.
   这两种鸟被一条狭窄的河流隔开。
2. 2. This process is often referred to as parapatric speciation.
   这个过程通常被称为并行分化。
3. 3. Parapatric speciation has been proposed as a mechanism for the evolution of new species.
   平行分化被提出为新物种进化的一种机制。