Inbreeding May Offer Long-Term Benefits: A Study on Svalbard Reindeer

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Reindeer have managed to adapt to life on Svalbard, despite the fact that they have only been on the islands for roughly 8,000 years. But will they be able to adapt to the rapid climate changes? (Image Credit: Bart Peeters)

The Arctic Archipelago of Svalbard has been home to reindeer for over 7000 years. Among the reindeer species in the far north, the Svalbard reindeer is distinct, having the most inbreeding and least genetic diversity, according to Nicolas Dussex, a postdoc at the Norwegian University of Science and Technology (NTNU).

Historical records suggest that reindeer first reached Svalbard between 7000-8000 years ago, possibly migrating from Russia. This limited migration might have led to a small founding population, which, according to evolutionary principles, could face genetic challenges due to inbreeding. However, the Svalbard reindeer population has flourished, now numbering over 20,000 animals.

Despite their low genetic diversity, these reindeer have adapted well to Arctic conditions. Distinct features include a smaller size, shorter legs, the ability to digest mosses when lichens are absent, and the capacity to alter their circadian rhythm to Svalbard's unique seasonal changes.

Research teams from NTNU and partnering institutions studied genetic samples from 91 reindeer to understand how they genetically differ from their mainland counterparts. Michael D. Martin, a professor at NTNU, emphasized the importance of studying such isolated populations for understanding genetic challenges.

Historically, the Svalbard reindeer population experienced a severe reduction, a phenomenon termed as a 'bottleneck' in population biology. High inbreeding levels can expose harmful genetic mutations, which can be detrimental. However, over time, such mutations can be phased out—a process known as 'purging'. "Paradoxically, in the long run, inbreeding can be beneficial," stated Dussex.

Evidence of this phenomenon is also seen in New Zealand's Kakapo parrots. After a long period of inbreeding, harmful genetic variants were eliminated, leading to a population resurgence.
Brage Bremset Hansen, a professor at NTNU, stated that the Svalbard reindeer are in a comparatively favorable genetic state. This discovery could alter the approach to studying the impacts of genetic bottlenecks. However, researchers aim to further understand the pace at which these harmful mutations are eliminated, utilizing DNA from ancient bone remains and antlers.

While the Svalbard reindeer have shown adaptability, there's uncertainty about their response to the accelerated changes due to global warming. The rapid warming in Svalbard, faster than any other global region, may challenge the reindeer's evolved adaptations.

Hansen expressed concerns about the reindeer's ability to adapt, potentially due to the loss of significant genetic variation. This challenge extends to other terrestrial animals with limited movement options in a changing climate. "But this work now provides us with a better basis for understanding how quickly species can adapt to new environments," noted Martin.

Read the original publication in iScience.