Skip to main content
Dryad

Data from: Homoploid hybrid speciation in a marine pelagic fish

Muto, Nozomu1; Su, Yong-Chao2; Hata, Harutaka3; Nguyen, Van Quan4; Vilasri, Veera5; Ghaffar, Mazlan Abd.6; Babaran, Ricardo P.7

Published Sep 17, 2025 on Dryad. https://doi.org/10.5061/dryad.kwh70rzdn

Data files

Sep 17, 2025 version files 583.94 MB

Click names to download individual files

Abstract

Homoploid hybrid speciation (HHS) is an enigmatic evolutionary process where new species arise through hybridization of divergent lineages without changes in chromosome number. Although increasingly documented in various taxa and ecosystems, convincing cases of HHS in marine fishes have been lacking. This study presents a possible case of HHS in a pelagic marine fish based on comprehensive genomic, morphological, and ecological analyses. Population genomics, species tree estimation, and tests of introgression and admixture identified three sympatric clusters in Megalaspis cordyla in the western Pacific and the admixed nature of one cluster between the others. Moreover, model-based demographic inference favored a hybrid speciation scenario over introgression for the origin of the admixed cluster. While contemporary gene flow suggested partial reproductive isolation, examination of occurrence data and ecologically relevant morphological characters suggested ecological differences between the clusters, potentially contributing to the reproductive isolation and niche partitioning in sympatry. The clusters are also morphologically distinguishable and thus can be taxonomically recognized as separate species. The hybrid cluster is restricted to the coasts of Taiwan and Japan, where all three clusters coexist. The parental clusters are additionally found in lower latitudes, where they display non-overlapping distributions. Given the geographical distributions, estimated times of the species formation, and patterns of historical demographic changes, we propose that the Pleistocene glacial cycles were the primary driver of HHS in this system. We also develop an ecogeographic model of HHS in marine coastal ecosystems, including a novel hypothesis to explain the initial stages of HHS.