 DNA sequencing of both mitochondrial and nuclear genes yielded relationships quite different ; 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 . The Dalmatian , pink @-@ backed and spot @-@ billed were all closely related to one another , while the Australian white pelican was their next @-@ closest relative . The great white pelican also belonged to this lineage but was the first to diverge from the common ancestor of the other four species . This finding suggests that pelicans evolved in the Old World and spread into the Americas , and that preference for tree- or ground @-@ nesting is more related to size than genetics . 
