Genomic diversity and differentiation between island and mainland populations of White‐tailed Eagles (Haliaeetus albicilla)

Using whole genome shotgun sequences from 92 white-tailed eagles
(Haliaeetus albicilla) sampled from Greenland, Iceland, Norway, Denmark,
Estonia, and Turkey between 1885–1950 and after 1990, we investigate the
genomic variation within countries over time, and between countries. Clear
signatures of ancient biogeographic substructure across Europe and the
North‐East Atlantic are observed. The greatest genomic differentiation was
observed between island (Greenland and Iceland) and mainland (Denmark,
Norway and Estonia) populations. The two island populations share a common
ancestry from a single mainland population, distinct from the other
sampled mainland populations, and despite the potential for high
connectivity between Iceland and Greenland they are well separated from
each other and are characterized by inbreeding and little variation.
Temporal differences also highlight a pattern of regional populations
persisting despite the potential for admixture. All sampled populations
generally showed a decline in effective population size over time, which
may have been shaped by four historical events: I) isolation of refugia
during the last glacial period 110‐115,000 years ago, II) population
divergence following the colonization of the deglaciated areas ~10,000
years ago, III) human population expansion, which led to the settlement in
Iceland ~1,100 years ago, and IV) human persecution and exposure to toxic
pollutants during the last two centuries.