This article is available from: http://www.biomedcentral.com/1471-2148/7/170
[Background] Dating of population divergence is critical in understanding speciation and in
evaluating the evolutionary significance of genetic lineages, upon which identification of
conservation and management units should be based. In this study we used a multilocus approach
and the Isolation-Migration model based on coalescence theory to estimate the time of divergence
of the Spanish and Eastern imperial eagle sister species. This model enables estimation of population
sizes at split, and inference of gene flow after divergence.
[Results] Our results indicate that divergence may have occurred during the Holocene or the late
Pleistocene, much more recently than previously suspected. They also suggest a large population
reduction at split, with an estimated effective population size several times smaller for the western
population than for the eastern population. Asymmetrical gene flow after divergence, from the
Eastern imperial eagle to the Spanish imperial eagle, was detected for the nuclear genome but not
the mitochondrial genome. Male-mediated gene flow after divergence may explain this result, and
the previously reported lower mitochondrial diversity but similar nuclear diversity in Spanish
imperial eagles compared to the Eastern species.
[Conclusion] Spanish and Eastern imperial eagles split from a common ancestor much more
recently than previously thought, and asymmetrical gene flow occurred after divergence. Revision
of the phylogenetic proximity of both species is warranted, with implications for conservation
This project
was funded by the Spanish Ministry of Science and Technology (Ref.:
REN2001-2310) and the I BBVA Foundation Awards for Scientific Research
in Conservation Biology in Spain to our Group of Conservation Biology of
Birds and their Habitats.
Peer reviewed