University of Oulu

Lan, T., Leppälä, K., Tomlin, C., Talbot, S. L., Sage, G. K., Farley, S. D., Shideler, R. T., Bachmann, L., Wiig, Ø., Albert, V. A., Salojärvi, J., Mailund, T., Drautz-Moses, D. I., Schuster, S. C., Herrera-Estrella, L., & Lindqvist, C. (2022). Insights into bear evolution from a Pleistocene polar bear genome. Proceedings of the National Academy of Sciences, 119(24), e2200016119.

Insights into bear evolution from a Pleistocene polar bear genome

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Author: Lan, Tianying1,2; Leppälä, Kalle3; Tomlin, Crystal1;
Organizations: 1Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260
2Daicel Arbor Biosciences, Ann Arbor, MI 48103
3Department of Mathematical Sciences, University of Oulu, 90014 Oulu, Finland
4Far Northwestern Institute of Art and Science, Anchorage, AK 99501
5Alaska Department of Fish and Game, Anchorage, AK 99518
6Alaska Department of Fish and Game, Fairbanks, AK 99701
7Natural History Museum, University of Oslo, 0318 Oslo, Norway
8School of Biological Sciences, Nanyang Technological University, Singapore 637551
9Organismal and Evolutionary Biology Research Programme, University of Helsinki, 00014 Helsinki, Finland
10Bioinformatics Research Centre, Aarhus University, 8000 Aarhus, Denmark
11Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551
12Laboratorio Nacional de Genómica para la Biodiversidad/Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del Instituto Politecnico Nacional, 36500 Irapuato, México
13Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79430
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.9 MB)
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Language: English
Published: National Academy of Sciences of the United States of America, 2022
Publish Date: 2023-05-26


The polar bear (Ursus maritimus) has become a symbol of the threat to biodiversity from climate change. Understanding polar bear evolutionary history may provide insights into apex carnivore responses and prospects during periods of extreme environmental perturbations. In recent years, genomic studies have examined bear speciation and population history, including evidence for ancient admixture between polar bears and brown bears (Ursus arctos). Here, we extend our earlier studies of a 130,000- to 115,000-y-old polar bear from the Svalbard Archipelago using a 10× coverage genome sequence and 10 new genomes of polar and brown bears from contemporary zones of overlap in northern Alaska. We demonstrate a dramatic decline in effective population size for this ancient polar bear’s lineage, followed by a modest increase just before its demise. A slightly higher genetic diversity in the ancient polar bear suggests a severe genetic erosion over a prolonged bottleneck in modern polar bears. Statistical fitting of data to alternative admixture graph scenarios favors at least one ancient introgression event from brown bears into the ancestor of polar bears, possibly dating back over 150,000 y. Gene flow was likely bidirectional, but allelic transfer from brown into polar bear is the strongest detected signal, which contrasts with other published work. These findings may have implications for our understanding of climate change impacts: Polar bears, a specialist Arctic lineage, may not only have undergone severe genetic bottlenecks but also been the recipient of generalist, boreal genetic variants from brown bears during critical phases of Northern Hemisphere glacial oscillations.

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Series: Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
ISSN-E: 1091-6490
ISSN-L: 0027-8424
Volume: 119
Issue: 24
Article number: e2200016119
DOI: 10.1073/pnas.2200016119
Type of Publication: A1 Journal article – refereed
Field of Science: 1181 Ecology, evolutionary biology
Funding: This work was supported by the National Fish and Wildlife Foundation and NSF (awards 1556565 and 1854550 to C.L.), Alaska Department of Fish and Game (to S.D.F. and R.T.S.), and US Geological Survey’s Changing Arctic Ecosystems (to S.L.T.), which is supported by funding from the Wildlife Program of the US Geological Survey Ecosystem Mission Area.
Copyright information: © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).