Retracing the response of Rangifer to postglacial climate change in
Arctic islands
Abstract
Aim: Rangifer tarandus L. play a key role in Arctic ecosystems as the
most numerous and widespread large herbivore. Sea ice is vital for
maintaining genetic connectivity in Arctic islands, yet the historical
role of sea ice in shaping Rangifer biogeography is unknown. We study
the timing of island dispersal and the role of sea ice changes and ice
sheet retreat since the last glacial period. Methods: We compiled
published datasets of mitochondrial DNA sequences which informed
population history scenarios, evaluated in a coalescent-based
approximate Bayesian computation (ABC) modelling framework to test
hypotheses of island (re)colonisation and to estimate timings of
divergence and admixture. Population events were compared with modelled
and proxy-based paleo-sea ice cover and published ice sheet
chronologies. Results: Our analysis supports Holocene dispersal onto
deglaciated Arctic islands rather than High Arctic glacial refugia. The
degree of population admixture and the effect of sea ice was dependent
on regional geography and climate history. North American initial island
population divergence occurred as sea ice cover was declining. A lack of
strong genetic structure and late Holocene admixture suggest that island
populations were somewhat connected by sea ice during the Holocene. The
Svalbard and West Greenland divergence times lagged deglaciation but
broadly align with fossil-based estimates of colonisation, suggesting
dispersal limitation due to sea ice conditions, potentially modulated by
ocean currents and sea ice drift. Main conclusions: Our study sheds
light on the Late Quaternary (~60 ka - present) history of
Arctic island Rangifer and suggests that ice sheet retreat, sea ice
cover, and ocean currents were important in shaping present-day genetic
patterns. Regional differences in postglacial dynamics suggest that
dispersal during contemporary climate change may vary regionally and
depend upon decreasing connectivity provided by sea ice.