The future of DNA-DNA hybridization studies.

This article draws on many vertebrate examples to assess the future of DNA-DNA hybridization studies. I first discuss whether applications of the method have reached the point of diminishing returns, or rather the start of a great leap forward, in our evolutionary understanding. Vertebrate groups whose relationships are especially likely to be illuminated include parrots, pigeons, bats, pinnipeds, mammalian carnivores, frogs, and rodents. There are at least two reasons why classifications based on DNA-DNA hybridization may prove to differ from classifications based on particular character, whether these be noncoding DNA sequences or protein sequences or anatomical characters. Because evolutionary relationships can now be deduced independently of anatomical characters, this should permit a renaissance in comparative anatomical studies of adaptation. The origin of major functional shifts from changes in a small fraction of the genome is illustrated by polar bears, sea otters, warblers, vultures, and especially by humans.