Distinct and extinct: genetic differentiation of the Hawaiian eagle

Eagles currently occur in the Hawaiian Islands only as vagrants, but Quaternary bones of Haliaeetus eagles have been found on three of the major islands. A previous study of a ∼3500-year-old skeleton from Maui found its mtDNA more similar to White-tailed (H. albicilla) than to Bald (H. leucocephalus) Eagles, but low intraspecific resolution of the markers and lack of comparative data from mainland populations precluded assessment of whether the individual was part of the diversity found in Eurasia, or whether it represented an endemic Hawaiian lineage. Using ancient DNA techniques, we sequenced part of the rapidly evolving mtDNA control region from the same specimen, and compared it to published range-wide control region data from White-tailed Eagles and newly generated sequences from Bald Eagles. Phylogenetic analyses indicated that the Hawaiian eagle represents a distinct (>3% divergent) mtDNA lineage most closely related to those of extant White-tailed Eagles. Based on fossil calibration, we estimate that the Hawaiian mtDNA lineage diverged from mainland sequences around the Middle Pleistocene. Although not clearly differentiated morphologically from mainland forms, the Hawaiian eagle thus likely constituted an isolated, resident population in the Hawaiian archipelago for more than 100,000 years, where it was the largest terrestrial predator.