Stable species boundaries despite ten million years of hybridization in tropical eels

Julia M I Barth (1) , Chrysoula Gubili (2) , Michael Matschiner (3, 4) , Ole K Tørresen (4) , Shun Watanabe (5) , Bernd Egger (1) , Yu-San Han (6) , Eric Feunteun (7, 8) , Ruben Sommaruga (9) , Robert Jehle (10) , Robert Schabetsberger (11)

1 Unibas - Université de Bâle = University of Basel = Basel Universität
2 HAO Demeter - Hellenic Agricultural Organization Demeter
3 UZH - Universität Zürich [Zürich] = University of Zurich
4 UiO - University of Oslo
5 Kindai University
6 Institute of Fisheries Science
7 BOREA - Biologie des Organismes et Ecosystèmes Aquatiques
8 CreSco - Centre de Recherche Sciences Sociales Sport et Corps
9 Leopold Franzens Universität Innsbruck - University of Innsbruck
10 University of Salford
11 FHS - Salzburg University of Applied Sciences = Fachhochschule Salzburg

Genomic evidence is increasingly underpinning that hybridization between taxa is commonplace , challenging our views on the mechanisms that maintain their boundaries. Here, we focus on seven catadromous eel species (genus Anguilla) and use genome-wide sequence data from more than 450 individuals sampled across the tropical Indo-Pacific, morphological information, and three newly assembled draft genomes to compare contemporary patterns of hybridization with signatures of past introgression across a time-calibrated phylogeny. We show that the seven species have remained distinct for up to 10 million years and find that the current frequencies of hybridization across species pairs contrast with genomic signatures of past introgression. Based on near-complete asymmetry in the directionality of hybridization and decreasing frequencies of later-generation hybrids, we suggest cytonuclear incompatibilities, hybrid breakdown, and purifying selection as mechanisms that can support species cohesion even when hybridization has been pervasive throughout the evolutionary history of clades.

Mots clés: Evolutionary genetics; Genetic hybridization; Phylogenetics; Population genetics

Domaines: Génétique

Julia M I Barth, Chrysoula Gubili, Michael Matschiner, Ole K Tørresen, Shun Watanabe, et al.. Stable species boundaries despite ten million years of hybridization in tropical eels. Nature Communications, 2020, 11 (1), ⟨10.1038/s41467-020-15099-x⟩. ⟨hal-02553699⟩