Convergent evolution and paraphyly of the hawk-eagles of the genus Spizaetus (Aves, Accipitridae) -: phylogenetic analyses based on mitochondrial markers

The phylogenetic relationships within the New and Old World hawk-eagle assemblage (genus Spizaetus; Aves: Accipitridae) were studied using mitochondrial DNA sequences (cytochrome b, control region). Eighty-four specimens representing all Spizaetus species and almost all currently distinguished subspecies as well as 11 other booted and non-booted 'eagle' genera from the Neotropics, Africa, Eurasia, South Asia and Australasia (Oroaetus, Harpia, Morphnus, Lophaetus, Stephanoaetus, Hieraaetus, Aquila, Ictinaetus, Spilornis, Pithecophaga, Harpyopsis) were investigated. Although the basal branching could not be resolved, our investigations clearly indicate that hawk-eagles represent a paraphyletic assemblage and thus their external similarities have to be ascribed to convergent evolution. The New World taxa of Spizaetus cluster together, but the South American species Oroaetus isidori appears embedded within this clade. The taxa from Southeast to East Asia form a clearly separated monophyletic group. It is further divided into two subgroups, which are also characterized by distinct juvenile plumage patterns. Spizaetus africanus, the only African representative of the genus, is found in a mixed cluster consisting of members of the genera Aquila and Hieraaetus. These findings are in accordance with previous studies of other authors based on various molecular markers and different sets of taxa, but disagree with current taxonomy. Therefore, we suggest assigning the species of the genus Spizaetus to three different genera: (1) Spizaetus (including Oroaetus isidori) in Central and South America and (2) Nisaetus for the Southeast to East Asian group. (3) The African taxon (Spizaetus africanus) is discussed to be included into the genus Aquila. Furthermore, we propose to use the former genus name Lophotriorchis Sharpe, 1874, for the monotypic species Hieraaetus kienerii, which has an isolated phylogenetic position.