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做过托福TPO31第一篇阅读的同学们一定会对物种形成 (Speciation) 这个生物学概念留下深刻印象，那么我们现在来系统地了解一下什么是物种形成。 一. 物种形成，即从旧物种中分化出来新物种的过程。 (Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.) 物种形成主要有四种模式： 异域性物种形成（Allopatric Speciation） 边域性物种形成（Peripatric Speciation） 临域性物种形成（Parapatric Speciation） 同域性物种形成（Sympatric Speciation） 二. 异域性物种形成或地理隔离：同一物种，由于如海洋、高山、沙漠等地理隔离，导致分布不连续，彼此间没有遗传基因的交换，渐渐演化为不同的物种。 （Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become vicariant, or isolated from each other to an extent that prevents or interferes with genetic interchange. This can be the result of population dispersal leading to emigration, or by geographical changes such as mountain formation, island formation, or large scale human activities. The vicariant populations then undergo genotypic or phenotypic divergence as: (a) they become subjected to different selective pressures, (b) they independently undergo genetic drift, and (c) different mutations arise in the gene pools of the populations.） 三. 生殖隔离：亲缘相近的种群，在自然条件下，不能交配；即使能交配，也不能产生后代，或不能产生可以生育的后代。 （The mechanisms of reproductive isolation are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced are sterile.） |
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