Including ancient DNA to understand implications of historical overharvest, recolonization and climate change for the genetic diversity and structure of high-Arctic wild Svalbard reindeer

Contemporary genetic material holds information from the past, but lineages that went extinct are lost. Integrating ancient DNA prior to and during, for instance, harvest bottlenecks enables in-depth insights into genetic diversity loss and changes in genetic population structure. The high-Arctic tundra preserves millennia of natural history in the form of antlers, bones and the ancient DNA they contain. Ancient (4000-400 yrs BP) and modern wild Svalbard reindeer whole-genomes are now being studied by the ColdRein project, revealing a strong genetic diversity turnover following historical overharvest (17th-20th centuries). The regional extirpations and subsequent recolonization phase in the 20th and 21st centuries caused loss of genetic diversity and strong population-genetic structuring, further amplified by reduced dispersal ability as sea-ice corridors diminished. The slow recolonization from four remnant populations was supplemented by translocations from a genetically diverse population, which led to comparatively less accumulation of genetic load. Thus, after millennia of natural selection in the absence of humans, the current genetic diversity of Svalbard reindeer is a result of direct (overharvest, translocations) and indirect (climate change, including loss of dispersal corridors) effects of anthropogenic selection. The evidence of past genetic erosion and isolation will play a major role in predictions of future population viability in this increasingly fragmented meta-population system undergoing the Earth’s most rapid climate change.