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Prickly postglacial pioneers: adaptation of threespine stickleback to freshwater influences fatty acid desaturase (FADS2) copy number in Southern Greenland
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  • Cameron Hudson,
  • Cornelia Twining,
  • Marvin Moosmann,
  • Ryan Greenway,
  • Philine Feulner,
  • Blake Matthews
Cameron Hudson
EAWAG Forschungszentrum für Limnologie

Corresponding Author:[email protected]

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Cornelia Twining
EAWAG Forschungszentrum für Limnologie
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Marvin Moosmann
Schweizerische Vogelwarte Sempach
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Ryan Greenway
University of Konstanz
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Philine Feulner
EAWAG Forschungszentrum für Limnologie
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Blake Matthews
EAWAG Forschungszentrum für Limnologie
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Abstract

The adaptation of marine fish to freshwater environments is a prodigious example of rapid evolution, and yet the underlying ecological causes of genomic and phenotypic differentiation are poorly understood for traits associated with lipid content and composition. Threespine stickleback (Gasterosteus aculeatus) have repeatedly colonized, and adapted to, freshwater habitats across the northern hemisphere. These freshwater populations often show elevated copy number of the fatty acid desaturase 2 gene (FADS2), which increases the biosynthetic capacity of ω-3 long-chain polyunsaturated fatty acids (LC-PUFA). The starkly lower content of LC-PUFA in freshwater compared to marine prey, especially docosahexaenoic acid (DHA), likely imposes strong positive selection on freshwater fish for either increased biosynthesis or greater dietary acquisition of LC-PUFA. The threespine stickleback populations in postglacial coastal lakes of Southern Greenland offer an exceptional opportunity to study how variation in the copy number of FADS2 is related to abiotic and biotic conditions of lakes and their morphometry. As expected, we found strong sexual dimorphism in FADS2 copy number in all populations (19 freshwater, 1 marine, and 1 brackish), and an increased dimorphism in some freshwater populations. We also found that FADS2 copy number was negatively correlated, for both males and females, with the abundance of copepods, which are a DHA-rich food source in the zooplankton community. Overall, our results suggest that the prey community context of lakes might influence the process of metabolic adaptation of marine fish colonizing freshwater ecosystems.
06 Jun 2024Submitted to Oikos
14 Jun 2024Reviewer(s) Assigned
12 Jul 2024Review(s) Completed, Editorial Evaluation Pending
17 Jul 2024Editorial Decision: Revise Major
08 Aug 20241st Revision Received
10 Aug 2024Assigned to Editor
10 Aug 2024Submission Checks Completed
10 Aug 2024Review(s) Completed, Editorial Evaluation Pending
16 Aug 2024Reviewer(s) Assigned
18 Sep 2024Editorial Decision: Accept