Local differentiation in the land snail, Helix aspersa , was extensively studied. In Bryan, Texas, snail populations have been differentiated along very short distances, such as on different sides of streets, due to very limited migration and chance events. The pie diagrams show the frequencies of different alleles.
Smaller objects lose heat faster, as a consequence.
Accumulation of genetic differences that manifest themselves in the phenotype may lead to the formation of clines, races and eventually new species. Species formation Different species, such as these meadowlarks, can be very similar in appearance, yet they do not interbreed. Sometimes phenotypically different populations, such as these warblers that were earlier regarded as distinct species, can easily interbreed and have fertile offspring. Left, myrtle warbler, right, Audubon's warbler. Phenotypic differences may arise or may become more pronounced due to selection for avoiding gene exchange or hybridization between populations.