Tange Olsen Morten, Löytynoja Ari, Valtonen Mia, Knudsen Steen W, Bang Sofie, Gunnersen Casper, Rosing-Asvid Aqqalu, Ferguson Steven H, Dietz Rune, Kovacs Kit M, Lydersen Christian, Jernvall Jukka, Auvinen Petri, Galatius Anders
Section for Molecular Ecology and Evolution, Globe Institute University of Copenhagen Copenhagen K Denmark.
Section for Marine Mammal Research, Department of Ecoscience Aarhus University Roskilde Denmark.
Ecol Evol. 2025 Mar 4;15(3):e71067. doi: 10.1002/ece3.71067. eCollection 2025 Mar.
Spatiotemporal environmental heterogeneity is a major evolutionary driver, which can cause profound phylogeographic complexity, particularly at the periphery of species ranges. Ringed seals display a highly disjoint distribution, occurring in high abundance throughout the circumpolar Arctic, as well as in the Baltic Sea, Lake Saimaa and Lake Ladoga. These relict Fennoscandian ringed seals were traditionally regarded as originating from a single colonisation event after the Last Glacial Maximum (LGM), but recent studies have challenged this perception. Here, we analyse 246 mitogenomes and 180 skulls to unravel the diversity and spatiotemporal pattern of diversification in Fennoscandian ringed seals. Contrary to previous assumptions, our results reveal a complex evolutionary history characterised by pre-LGM diversification from Arctic ringed seals and possibly several Fennoscandian colonisation events. We hypothesise that Saimaa seals originate from Arctic ringed seals, from which they diverged prior to their arrival in Lake Saimaa. Ladoga seals appear to also originate from the Arctic, with secondary colonisation events from paleo-Skagerrak-Kattegat-Baltic, while the Baltic ringed seals have mixed evolutionary origins. Lake Saimaa and, to some extent, Lake Ladoga ringed seals have experienced a loss of diversity and evolved divergent skull morphologies, likely as a result of colonisation bottlenecks, isolation and dietary specialisation, while Baltic Sea ringed seals have retained remarkably high levels of genetic and morphological diversity. Our study supports the classification of Saimaa, Ladoga and Baltic ringed seals as distinct taxa and highlights the need for management and conservation efforts to mitigate cumulative impacts of human activities and climate change on Fennoscandian ringed seals.
时空环境异质性是一个主要的进化驱动力，它会导致深刻的系统地理学复杂性，尤其是在物种分布范围的边缘。环斑海豹呈现出高度不连续的分布，在整个环北极地区以及波罗的海、塞马湖和拉多加湖大量出现。这些斯堪的纳维亚半岛的残留环斑海豹传统上被认为起源于末次盛冰期（LGM）之后的一次单一殖民事件，但最近的研究对这一观点提出了挑战。在这里，我们分析了246个线粒体基因组和180个头骨，以揭示斯堪的纳维亚半岛环斑海豹多样性和时空分化模式。与之前的假设相反，我们的结果揭示了一个复杂的进化历史，其特征是在末次盛冰期之前与北极环斑海豹分化，并且可能有几次斯堪的纳维亚半岛的殖民事件。我们假设塞马湖海豹起源于北极环斑海豹，它们在到达塞马湖之前就与之分化。拉多加湖海豹似乎也起源于北极，有来自古斯卡格拉克-卡特加特-波罗的海的二次殖民事件，而波罗的海环斑海豹有混合的进化起源。塞马湖以及在一定程度上拉多加湖的环斑海豹经历了多样性丧失，并进化出了不同的头骨形态，这可能是由于殖民瓶颈、隔离和饮食特化造成的，而波罗的海环斑海豹保留了非常高的遗传和形态多样性水平。我们的研究支持将塞马湖、拉多加湖和波罗的海环斑海豹分类为不同的分类单元，并强调需要进行管理和保护努力，以减轻人类活动和气候变化对斯堪的纳维亚半岛环斑海豹的累积影响。
