No abstract

Greater and lesser spotted eagles (Aquila clanga, A. pomarina) are two closely related forest eagles overlapping in breeding range in east-central Europe. In recent years a number of mixed pairs have been observed, some of which fledged hybrid young. Here we use mitochondrial (control region) DNA sequences and AFLP markers to estimate genetic differentiation and possible gene flow between these species. In a sample of 83 individuals (61 pomarina, 20 clanga, 2 F1-hybrids) we found 30 mitochondrial haplotypes which, in a phylogenetic network, formed two distinct clusters differing on average by 3.0% sequence divergence. The two species were significantly differentiated both at the mitochondrial and nuclear (AFLP) genetic level. However, five individuals with pomarina phenotype possessed clanga-type mtDNA, suggesting occasional gene flow. Surprisingly, AFLP markers indicated that these ''mismatched'' birds (originating from Germany, E Poland and Latvia) were genetically intermediate between the samples of individuals in which mtDNA haplotype and phenotype agreed. This indicates that mismatched birds were either F1 or recent back-cross hybrids. Mitochondrial introgression was asymmetrical (no pomarina haplotype found in clanga so far), which may be due to assortative mating by size. Gene flow of nuclear markers was estimated to be about ten times stronger than for mtDNA, indicating a sex-bias in hybrid fertility in accordance with Haldane's rule. Hybridization between the two species may be more frequent and may occur much further west than hitherto assumed. This is supported by the recent discovery of a mixed pair producing at least one fledgling in NE Germany.

We present a phylogeny of all booted eagles (38 extant and one extinct species) based on analysis of published sequences from seven loci. We find molecular support for five major clades within the booted eagles: Nisaetus (10 species), Spizaetus (4 species), Clanga (3 species), Hieraaetus (6 species) and Aquila (11 species), requiring generic changes for 14 taxa. Additionally, we recommend that the Long-crested Eagle (Lophaetus occipitalis) and the Black Eagle (Ictinaetus malaiensis) remain in their monotypic genera, due to their distinctive morphology. We apply the recently resurrected genus Clanga for the spotted eagles (previously Aquila spp.) to resolve the paraphyly of the genus Aquila such that the clade including the Booted Eagle (H. pennatus), Little Eagle (H. morphnoides), Pygmy Eagle (H. weiskei), Ayres's Eagle (H. ayresii) and Wahlberg's Eagle (H. wahlbergi) can remain in the genus Hieraaetus. The Rufous-bellied Eagle should be retained in the genus Lophotriorchis. For consistency in English names, we recommend that the term "hawk-eagles" be used only for the species in the genera Nisaetus and Spizaetus. We suggest following new or modified English names: Cassin's Eagle (Aquila africana), Bonaparte's Eagle (A. spilogaster), Ayres's Eagle (Hieraaetus ayresii), and Black-and-chestnut Hawk-Eagle (Spizaetus isidori).