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Molecular footprints of Quaternary climate fluctuations in the circumpolar tundra shrub dwarf birch

Abstract:

The Arctic tundra biome is undergoing rapid shrub expansion (“shrubification”) in response to anthropogenic climate change. During the previous ~2.6 million years, glacial cycles caused substantial shifts in Arctic vegetation, leading to changes in species’ distributions, abundance, and connectivity, which have left lasting impacts on the genetic structure of modern populations. Examining how shrubs responded to past climate change through genetic data reveals the demographic dynamics that shaped their current diversity and distribution and sheds light on the resilience of Arctic shrubs.

Here we test scenarios of Quaternary demographic history of dwarf birch species (Betula nana L. and Betula Glandulosa Michx.) using Single Nucleotide Polymorphism (SNP) markers obtained from RAD sequencing and approximate Bayesian computation. We compare the timings of modelled population events with ice sheet reconstructions and other paleoenvironmental information to untangle the impacts of alternating cold and warm periods on dwarf birch.

Our best supported model suggested that the species diverged in the Mid-Pleistocene Transition as glaciations intensified. We found support for a complex history of inter- and intraspecific divergences and gene flow, and secondary contact occurred during both ice sheet expansion and retreat.

Our spatiotemporal analysis suggests that the modern genetic structure of dwarf birch results from transitions in climate between glacials and interglacials, with ice sheets acting alternatively as a barrier or an enabler of population mixing. Tundra shrubs may have had more nuanced responses to past climatic changes than phylogeographic analyses have often suggested, with implications for future eco-evolutionary responses to anthropogenic climate change.

Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1111/mec.70082

Authors

More by this author
Institution:
University of Oxford
Division:
SSD
Department:
SOGE
Role:
Author
ORCID:
0000-0003-1720-4475
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Oxford college:
St Hugh's College
Role:
Author
ORCID:
0000-0002-0370-9897


More from this funder
Funder identifier:
https://ror.org/012mzw131
Grant:
PLP-2021-243
More from this funder
Funder identifier:
https://ror.org/02b5d8509
Grant:
NE/V011405/1


Publisher:
Wiley
Journal:
Molecular Ecology More from this journal
Volume:
34
Issue:
19
Article number:
e70082
Publication date:
2025-09-02
Acceptance date:
2025-08-05
DOI:
EISSN:
1365-294X
ISSN:
0962-1083


Language:
English
Keywords:
Pubs id:
2268898
Local pid:
pubs:2268898
Deposit date:
2025-08-06
ARK identifier:

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