Galapagos in the context of "HMS Beagle"

Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, sometimes leading to speciation. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that cause adaptations. After many generations and continual evolution, the populations become less able to interbreed with one another. The American naturalist J. T. Gulick (1832–1923) was the first to use the term "divergent evolution", with its use becoming widespread in modern evolutionary literature. Examples of divergence in nature are the adaptive radiation of the finches of the Galápagos, changes in mobbing behavior of the kittiwake, and the evolution of the modern-day dog from the wolf.

The term can also be applied in molecular evolution, such as to proteins that derive from homologous genes. Both orthologous genes (resulting from a speciation event) and paralogous genes (resulting from gene duplication) can illustrate divergent evolution. Through gene duplication, it is possible for divergent evolution to occur between two genes within a species. Similarities between species that have diverged are due to their common origin, so such similarities are homologies.

The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches generally have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where they are usually resident and do not migrate. They have a worldwide native distribution except for Australia and the polar regions. The family Fringillidae contains more than two hundred species divided into fifty genera. It includes the canaries, siskins, redpolls, serins, grosbeaks and euphonias, as well as the morphologically divergent Hawaiian honeycreepers.

Many birds in other families are also commonly called "finches". These groups include the estrildid finches (Estrildidae) of the Old World tropics and Australia; some members of the Old World bunting family (Emberizidae) and the New World sparrow family (Passerellidae); and the Darwin's finches of the Galapagos islands, now considered members of the tanager family (Thraupidae).

Buddleja americana is the most widespread of all the Buddleja species native to the Americas, its range extending south from Tamaulipas, Mexico, through Central America and much of the West Indies into South America, reaching eastward to Venezuela, westward as far as the Galapagos, and south to Bolivia. It occurs at elevations from sea level to 2500 m, in a variety of habitats, including cloud forest, mountain savanna, pine–oak forest, and rocky slopes near rivers. It also invades fields and roadsides.

The species was originally named and described by Linnaeus in 1753.