Divergent evolution

Divergent evolution, also called divergent selection, is the accumulation of differences between closely related populations of the same species, a process that can eventually lead to speciation. It occurs when populations become separated by some barrier and then experience different selective pressures and different patterns of genetic drift, so that over time enough evolutionary distance builds up that the populations can no longer interbreed, whether because of physiological or behavioral barriers. Darwin's finches of the Galapagos Islands are the classic example: descended from a common ancestor, the various finch species Darwin observed had evolved beaks of very different shapes and sizes, from short beaks suited to cracking seeds to elongated beaks for catching insects and others adapted to feeding on cactus, each shaped by the particular food sources available on its own island.