Genomic diversity and differentiation between island and mainland
populations of White-tailed Eagles (Haliaeetus albicilla)
Abstract
Divergence in the face of high dispersal capabilities is a documented
but poorly understood phenomenon. The white-tailed eagle (Haliaeetus
albicilla) has a large geographic dispersal capability and should
theoretically be able to maintain genetic homogeneity across its
dispersal range. However, following analysis of the genomic variation of
white-tailed eagles, from both historical and contemporary samples,
clear signatures of ancient biogeographic substructure across Europe and
the North-East Atlantic is 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.