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| Kangia ringed seals Pusa hispida hispida in the Ilulissat Icefjord system, West Greenland (c) Pelage of Kangia (left) and typical Arctic ringed seals (right). in Rosing-Asvid, Löytynoja, Momigliano, Hansen, ... et Olsen, 2023. DOI: 10.1111/mec.17163 All photographs by Greenland Institute of Natural Resources. |
Abstract
The Earth's polar regions are low rates of inter- and intraspecific diversification. An extreme mammalian example is the Arctic ringed seal (Pusa hispida hispida), which is assumed to be panmictic across its circumpolar Arctic range. Yet, local Inuit communities in Greenland and Canada recognize several regional variants; a finding supported by scientific studies of body size variation. It is however unclear whether this phenotypic variation reflects plasticity, morphs or distinct ecotypes. Here, we combine genomic, biologging and survey data, to document the existence of a unique ringed seal ecotype in the Ilulissat Icefjord (locally ‘Kangia’), Greenland; a UNESCO World Heritage site, which is home to the most productive marine-terminating glacier in the Arctic. Genomic analyses reveal a divergence of Kangia ringed seals from other Arctic ringed seals about 240 kya, followed by secondary contact since the Last Glacial Maximum. Despite ongoing gene flow, multiple genomic regions appear under strong selection in Kangia ringed seals, including candidate genes associated with pelage coloration, growth and osmoregulation, potentially explaining the Kangia seal's phenotypic and behavioural uniqueness. The description of ‘hidden’ diversity and adaptations in yet another Arctic species merits a reassessment of the evolutionary processes that have shaped Arctic diversity and the traditional view of this region as an evolutionary freezer. Our study highlights the value of indigenous knowledge in guiding science and calls for efforts to identify distinct populations or ecotypes to understand how these might respond differently to environmental change.
Keywords: arctic, diversity, indigenous knowledge, local adaptation, marine mammal
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| Unusual population of ringed seals in the Ilulissat Icefjord system, West Greenland. (a) Kangia ringed seals hauling out on sea ice. (b) The dynamic Ilulissat Icefjord system. (c) Pelage of Kangia (left) and typical Arctic ringed seals (right). (d) Kangia ringed seal instrumented with a satellite tag (image edited to remove person in background. Original image provided in (d). (e) Typical Arctic ringed seal instrumented with a satellite tag (movement data not shown). All photographs by Greenland Institute of Natural Resources. |
CONCLUSION:
The discovery of a distinct ringed seal ecotype in the Ilulissat Icefjord adds to a growing list of Arctic marine species with newly detected genetic and/or phenotypic diversity (Bringloe et al., 2020; Jacobsen et al., 2022; Laidre et al., 2022; Madsen et al., 2016; Mathiesen et al., 2017; Tempestini et al., 2020). The Arctic environment is highly dynamic, with marine systems characterized by long- and short-term fluctuations in glacial extent and run-off, marine-freshwater clines, sea-level changes and isostatic rebound. These processes might facilitate both regional and local speciation, perhaps down to the scale of individual fjord systems or larger marine-terminating glacier fronts. Thus, while our study is the first to demonstrate the existence of a distinct Kangia ringed seal ecotype in the Ilulissat Icefjord, similar intraspecific diversity and differentiation may exist elsewhere in both ringed seals and other Arctic marine species. Across the Arctic, marine-terminating glaciers, deep fjord systems and polynyas sustain high biological productivity and provide important foraging and resting habitats for marine organisms (Heide-Jørgensen et al., 2016; Lydersen et al., 2014; Meire et al., 2017). These areas may have constituted important high-latitude refugia and even micro-evolutionary speciation factories through glacial and interglacial periods, potentially supporting uniquely adapted populations of otherwise wide-spread and seemingly panmictic Arctic marine organisms. Some local populations may not easily respond to climate change by simply tracking their habitat northward, whereas others may harbour the adaptive potential providing species-level resistance to current climate warming. Our findings highlight the need for dedicated scientific efforts and thorough sampling to record and understand regional and local drivers of intraspecific diversity in the Arctic to provide information for nature management.
Aqqalu Rosing-Asvid, Ari Löytynoja, Paolo Momigliano, Rikke Guldborg Hansen, Camilla Hjorth Scharff-Olsen, Mia Valtonen, Juhana Kammonen, Rune Dietz, Frank Farsø Rigét, Steve H. Ferguson, Christian Lydersen, Kit M. Kovacs, David M. Holland, Jukka Jernvall, Petri Auvinen and Morten Tange Olsen. 2023. An evolutionarily distinct Ringed Seal in the Ilulissat Icefjord. Molecular Ecology. DOI: 10.1111/mec.17163
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