An evolutionarily distinct ringed seal in the Ilulissat Icefjord

Area of Science:

• Marine Mammal Genetics
• Arctic Ecology
• Evolutionary Biology

Background:

• Polar regions exhibit low diversification rates, with Arctic ringed seals (Pusa hispida hispida) traditionally considered panmictic.
• Local indigenous knowledge and studies on body size variation suggest regional differences in ringed seals, but their nature (plasticity, morphs, or ecotypes) remains unclear.

Purpose of the Study:

• To investigate the existence of a unique ringed seal ecotype in Greenland's Ilulissat Icefjord (Kangia).
• To combine genomic, biologging, and survey data to characterize this potential ecotype and its evolutionary history.

Main Methods:

• Genomic analysis to determine population divergence and gene flow.
• Biologging and survey data to assess phenotypic and behavioral uniqueness.
• Analysis of genomic regions under selection, including candidate genes for specific traits.

Main Results:

• Identification of a distinct ringed seal ecotype in the Ilulissat Icefjord, diverging approximately 240,000 years ago.
• Genomic evidence of secondary contact post-Last Glacial Maximum and ongoing gene flow.
• Detection of strong selection in multiple genomic regions, including genes related to coloration, growth, and osmoregulation, explaining unique traits.

Conclusions:

• The study identifies 'hidden' diversity and adaptations within Arctic ringed seals, challenging the 'evolutionary freezer' hypothesis for polar regions.
• Highlights the importance of integrating indigenous knowledge with scientific research to uncover unique ecotypes.
• Emphasizes the need to identify distinct populations for understanding differential responses to environmental change.