 The eight living pelican species were traditionally divided into two groups, one containing four ground-nesters with mainly white adult plumage (Australian, Dalmatian, great white, and American white pelicans), and one containing four grey- or brown-plumaged species which nest preferentially either in trees (pink-backed, spot-billed and brown pelicans), or on sea rocks (Peruvian pelican).The largely marine brown and Peruvian pelicans, formerly considered conspecific, are sometimes separated from the others by placement in the subgenus "Leptopelicanus" but in fact species with both sorts of appearance and nesting behavior are found in either.DNA sequencing of both mitochondrial and nuclear genes yielded quite different relationships; the three New World pelicans formed one lineage, with the American white pelican sister to the two brown pelicans, and the five Old World species the other.