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Genomic footprints of hybridization in North Atlantic eels (Anguilla anguilla and A. rostrata)
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  • Aja Tengstedt,
  • Shenglin Liu,
  • Magnus Jacobsen,
  • Gabriela Ulmo Diaz,
  • Bjarni Jónsson,
  • José Martin Pujolar,
  • Michael Hansen
Aja Tengstedt
Aarhus University Department of Biology

Corresponding Author:[email protected]

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Shenglin Liu
Aarhus University Department of Biology
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Magnus Jacobsen
Technical University of Denmark National Institute of Aquatic Resources Silkeborg
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Gabriela Ulmo Diaz
Université Laval
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Bjarni Jónsson
North West Iceland Nature Center
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José Martin Pujolar
Technical University of Denmark National Institute of Aquatic Resources
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Michael Hansen
Aarhus University Department of Biology
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Abstract

European (Anguilla anguilla) and American eel (A. rostrata) represent a remarkable case of interspecific hybridization. They are both panmictic and spawn in partial sympatry in the Sargasso Sea, occasionally producing viable, fertile hybrids, primarily found in Iceland. We studied introgressive hybridization from American into European eel based on whole-genome sequences of 78 individuals, encompassing European, American and 21 putative hybrid eels. Previous studies using few genetic markers could not resolve whether hybridization involved simple unidirectional backcrossing or a more complex hybrid swarm scenario. However, local ancestry inference along individual chromosomes revealed Icelandic hybrids were primarily F1 hybrids or first-generation backcrosses toward European eel, with a few showing more complex backcrossing histories. All European eels outside Iceland contained short chromosomal blocks from American eel, indicating a porous genome. We found no evidence for previously stated hypotheses about geographical gradients of introgression in European eel outside Iceland. Several chromosomal regions showed high divergence between the species, but haplotype blocks introgressed from American eel were identified both within and outside these regions. There was little correspondence between regions of high relative and high absolute divergence (dXY), and they presumably reflect selective sweeps within species or regions of reduced recombination rather than barrier loci. We identified a single genomic region with evidence of introgression from American into European eel at multiple occasions, under positive selection in both species. Thus, although the two species maintain genetic integrity, their gene pools are not independent and represent a common pool of standing variation for future adaptive responses.
16 Jul 2024Submitted to Molecular Ecology
17 Jul 2024Submission Checks Completed
17 Jul 2024Assigned to Editor
17 Jul 2024Review(s) Completed, Editorial Evaluation Pending
13 Aug 2024Reviewer(s) Assigned
10 Oct 2024Editorial Decision: Revise Minor