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

• Published in: Peer Community Journal
• Main Authors: Fraïsse, Christelle, Haguenauer, Anne, Gérard, Karin, Anh-Thu Weber, Alexandra, Bierne, Nicolas, Chenuil, Anne
• Other Authors: Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement IRD : UR226-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Avignon Université (AU)-Aix Marseille Université (AMU)-Institut de recherche pour le développement IRD : UMR237-Centre National de la Recherche Scientifique (CNRS), Laboratorio de Ecología de Macroalgas Antárticas y Sub antárticas (LEMAS), Universidad de Magallanes (UMAG)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Kerguelen; Kerguelen Islands; Southern Ocean
• Online Access: https://hal.science/hal-03501373; https://hal.science/hal-03501373/document; https://hal.science/hal-03501373/file/10_24072_pcjournal_18.pdf; https://doi.org/10.24072/pcjournal.18

International audience 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.