Scandinavian brown bears have endured a complex history, from their post-glacial recolonization to a dramatic population decline in the 20th century. A team of researchers has now shed new light on this fascinating story by analyzing ancient, historical, and modern mitochondrial genomes of these iconic animals. Their findings reveal insights into the bears’ maternal lineages, the impacts of past climate changes, and the consequences of human persecution. This comprehensive study not only enhances our understanding of phylogeography and conservation genetics, but also highlights the resilience and adaptability of these remarkable creatures. Join us as we delve into the genetic tapestry that weaves the tale of Scandinavia’s brown bears.
Tracing the Footsteps of Recolonization
After the last ice age, as the Fennoscandian ice sheet retreated, Click Here
 began to recolonize Scandinavia. Previous research based on short mitochondrial DNA sequences suggested that this recolonization occurred from two distinct directions: bears from Western European refugia entered Scandinavia through the southern route, while bears from Eastern European refugia expanded into the northern regions.</p>
<p><figure class="wp-block-image size-large"><img decoding="async" src="https://famefreq.s3.us-east-2.amazonaws.com/1729757833_41598_2024_75028_Fig1_HTML.png" alt="figure 1" class="wp-image-1" /><figcaption class="wp-element-caption">Fig. 1</figcaption></figure>
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<p>The new study by Feinauer and colleagues takes a deeper dive into this process by analyzing 41 ancient, historical, and modern mitochondrial genomes of Scandinavian brown bears. Their findings provide a more nuanced understanding of the recolonization event.</p>
<p><h3>Unraveling the Maternal Lineages</h3>
<p>The researchers’ phylogenetic analysis revealed that the southern Scandinavian brown bears belong to the Western European mitochondrial clade 1a, while the northern bears carry the Eastern European clade 3a. This confirms the previously proposed bi-directional recolonization pattern.</p>
<p><figure class="wp-block-image size-large"><img decoding="async" src="https://famefreq.s3.us-east-2.amazonaws.com/1729757837_41598_2024_75028_Fig2_HTML.png" alt="figure 2" class="wp-image-2" /><figcaption class="wp-element-caption">Fig. 2</figcaption></figure>
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<p>However, the team also found that the southern Scandinavian bears were not recolonized by a single maternal lineage, but rather by multiple lineages from clade 1a. The estimated divergence times of these lineages indicate that the southern region was likely recolonized in multiple waves, either simultaneously or sequentially, during the early Holocene. In contrast, the northern Scandinavian bears appear to have been recolonized by a single mitochondrial lineage from clade 3a.</p>
<p><h3>Weathering the Bottleneck</h3>
<p>The Scandinavian brown bear population experienced a dramatic decline in the early 20th century due to intense human persecution, with the population plummeting to only around 130 individuals. The researchers’ analysis of the mitochondrial data reveals the impact of this “bottleneck” event on the bears’ genetic diversity.</p>
<p><figure class="wp-block-image size-large"><img decoding="async" src="https://famefreq.s3.us-east-2.amazonaws.com/1729757840_41598_2024_75028_Fig3_HTML.png" alt="figure 3" class="wp-image-3" /><figcaption class="wp-element-caption">Fig. 3</figcaption></figure>
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<p>Before the bottleneck, the southern Scandinavian bears exhibited high mitochondrial diversity, with each individual carrying a unique haplotype. However, the recent population decline has resulted in the loss of all but one haplotype in the southern subpopulation. In contrast, the northern Scandinavian bears retained most of their pre-bottleneck haplotypes, suggesting a less severe impact on their mitochondrial diversity.</p>
<p><h3>Implications and Future Directions</h3>
<p>This study not only enhances our understanding of the Scandinavian brown bears’ <b>phylogeographic history</b> and the genetic consequences of recent population declines, but also highlights the importance of <b>conservation genetics</b> in guiding management strategies.</p>
<p><figure class="wp-block-image size-large"><img decoding="async" src="https://famefreq.s3.us-east-2.amazonaws.com/1729757843_41598_2024_75028_Fig4_HTML.png" alt="figure 4" class="wp-image-4" /><figcaption class="wp-element-caption">Fig. 4</figcaption></figure>
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<p>The findings suggest that the southern Scandinavian brown bears may have been more vulnerable to the bottleneck, potentially due to their lower effective population size or other factors. This information can inform targeted conservation efforts to support the recovery and genetic diversity of the southern subpopulation.</p>
<p>Looking ahead, the researchers emphasize the need for further investigations using <b>genome-wide markers</b> to gain a more comprehensive understanding of the Scandinavian brown bears’ evolutionary history and population dynamics. Integrating these insights with the mitochondrial data can provide a more nuanced picture of how past climate changes and human impacts have shaped the genetic landscape of these remarkable animals.</p>
<p>Author credit: This article is based on research by Isabelle Sofie Feinauer, Edana Lord, Johanna von Seth, Georgios Xenikoudakis, Erik Ersmark, Love Dalén, Ioana-Nicoleta Meleg.</p>
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