第2个回答 2017-02-24
Populations of a species that are spread out over a broad geographical range are often arrayed in a cline-a gradual change in one or more characteristics as each population evolves adaptations to its own local environment. Along a cline, subspecies with distinct characteristics may arise. Often, individuals at either end of a cline are reproductively isolated.
地域上分布很广的种的群体中,经常存在变异群,因为适应当地的环境,每个群体逐渐产生一个或多个与众不同的特点。在变异群中,带有明显特征的亚群可能产生。通常,在两个变异群中的个体是繁殖隔离的。