Published October 24, 2018 | Version 4
Preprint Open

Fine-grained habitat-associated genetic connectivity in an admixed population of mussels in the small isolated Kerguelen Islands

  • 1. Institute of Science and Technology Austria: Vienna
  • 2. Institut Mediterraneen de Biodiversite et d'Ecologie marine et continentale, France
  • 3. Lab de Ecosistemas Marinos Antarticos y Subantarticos, Inst de la Patagonia, Chile
  • 4. Zoological Institute, University of Basel, Switzerland
  • 5. Institut des Sciences de l'Evolution UMR5554, University Montpellier, France

Description

Reticulated evolution -i.e. secondary introgression/admixture between sister taxa- is increasingly recognized as playing a key role in structuring infra-specific genetic variation and revealing cryptic genetic connectivity patterns. When admixture zones coincide with ecological transitions, the connectivity patterns often follow environmental variations better than distance and introgression clines may easily be confounded with local adaptation signatures. The Kerguelen mussels is an ideal system to investigate the potential role of admixture in enhancing micro-geographic structure, as they inhabit a small isolated island in the Southern Ocean characterized by a highly heterogeneous environment. Furthermore, genomic reticulation between Northern species (M. edulis, M. galloprovincialis and M. trossulus) and Southern species (M. platensis: South America and the Kerguelen Islands; and M. planulatus: Australasia) has been suspected. Here, we extended a previous analysis by using targeted-sequencing data (51,878 SNPs) across the three Northern species and the Kerguelen population. Spatial structure in the Kerguelen was then analyzed with a panel of 33 SNPs, including SNPs that were more differentiated than the genomic average between Northern species (i.e., ancestry-informative SNPs). We first showed that the Kerguelen lineage splitted very shortly after M. edulis and M. galloprovincialis initiated speciation, and it subsequently experienced admixture with the three Northern taxa. We then demonstrated that the Kerguelen mussels were significantly differentiated over small spatial distance, and that this local genetic structure was associated with environmental variations and mostly revealed by ancestry-informative markers. Simulations of admixture in the island highlight that genetic-environment associations can be better explained by introgression clines between heterogeneously differentiated genomes than by adaptation.

A preprint peer-reviewed and recommended by Peer Community in Evolutionary Biology. https://doi.org/10.1101/239244

Notes

A preprint peer-reviewed and recommended by Peer Community in Evolutionary Biology. https://doi.org/10.1101/239244

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Related works

Is supplemented by
10.5061/dryad.6k740 (DOI)