The formation of new species. This typically involves the establishment of barriers (isolating mechanisms) that prevent two populations from interbreeding (see allopatric , sympatric ). Natural selection may then occur, taking the two populations along different evolutionary paths so that they become progressively different from each other. Speciation is often regarded as a relatively slow process, especially in the animal kingdom (but see punctuated equilibrium ). In the plant kingdom, however, a major contribution to speciation is polyploidy. This may establish a new population (species) in a single generation that is incapable of reproducing with either parent. Polyploidy has thus been cited as an example of 'instant evolution'. See also adaptive radiation , neoteny. |
