Mitochondrial DNA Analysis Reveals Multiple Lineages within the Redtoothed Triggerfish, Odonus niger: Formal Description of Odonus indopacificus sp. nov. and Odonus indicus sp. nov.

This research was initiated to determine whether the redtoothed triggerfish Odonus niger—historically considered a single, widely distributed species across the Indo-Pacific and the Red Sea—actually constitutes a complex of multiple, morphologically similar species. Through a comprehensive molecular investigation based on the global alignment of mitochondrial cytochrome c oxidase subunit I (COI) gene sequences, anchored exclusively to traceable physical voucher specimens, the genetic and biogeographical structure of this taxon was thoroughly analyzed. The results unequivocally demonstrate that the true nominal species Odonus niger represents a genetically well-defined clade geographically restricted to the Arabian basin, the Red Sea, and the Western Indian Ocean (extending to the La Réunion area), thereby invalidating the historical hypothesis of a single, continuous panmictic distribution. Extending genetic comparisons to the remaining basins led to the discovery and formal description of two novel, independent evolutionary lineages. The first, diagnosed herein as Odonus indopacificus sp. nov., exhibits the most expansive distribution, extending continuously from the coast of South Africa to the central Pacific waters of French Polynesia, encompassing the entire Indonesian archipelago. The second, formalized as Odonus indicus sp. nov., emerges as a third distinct evolutionary entity, endemic to the waters of Sri Lanka and the adjacent Indian subcontinent. This taxonomic revision definitively dismantles the outdated paradigm of a single, ubiquitous taxon across the tropical Indo-Pacific, elucidating the complex cryptic biodiversity of the genus Odonus and providing a robust scientific foundation for understanding the ecological roles these distinct evolutionary lineages fulfill within their respective coral reef ecosystems.The tropical marine ecosystems of the Indo-Pacific and the Red Sea harbor an extraordinary concentration of biodiversity. Within these habitats, triggerfishes (family Balistidae) occupy paramount ecological niches, actively contributing to the trophic and ethological dynamics of coral reefs. Historically, the genus Odonus Gistel, 1848, has been universally treated in the scientific literature as a monotypic taxon, represented exclusively by the redtoothed triggerfish, Odonus niger (Rüppell, 1836). For over a century, the paradigm of a single species widely distributed from the eastern coast of Africa to the central Pacific has been sustained by pronounced morphological conservatism. Its unmistakable appearance—characterized by a deep blue to purplish body, reddish teeth, and a distinctly lunate caudal fin—led marine biologists to interpret any local phenotypic variation as mere natural intraspecific fluctuation, effectively discouraging further taxonomic scrutiny for a prolonged period.In recent decades, however, the integration of molecular systematics—particularly the employment of the mitochondrial cytochrome c oxidase subunit I (COI) gene as a genetic marker—has unequivocally demonstrated that morphological uniformity in marine teleosts frequently conceals complexes of cryptic, or at least highly similar, species. Entities previously considered to be single populations dispersed across vast oceanic basins have frequently been revealed as mosaics of distinct, isolated evolutionary lineages. This type of investigation is increasingly facilitated by the growing availability of genetic data shared through public databases such as GenBank. Nevertheless, for these molecular data to translate into robust taxonomic revisions, it is imperative that the utilized genetic sequences remain strictly associated with voucher specimens (traceable and cataloged physical specimens), thereby ensuring the absolute objectivity and reproducibility of the analyses.The present study critically re-evaluates the phylogeographic and taxonomic structure of the genus Odonus across its extensive native range. By leveraging a comprehensive global comparative molecular analysis based on COI sequences strictly tied to certified physical vouchers, this research definitively refutes the historical hypothesis of a single species homogeneously distributed across the Red Sea and the Indo-Pacific. Indeed, our results demonstrate that, concealed beneath an apparent morphological immutability, there exists a clear macro-structure composed of three independent species. Beyond the reassignment of the nominal species O. niger to a specific, restricted geographic range, this study identifies and formalizes two novel evolutionary lineages previously unrecognized by science: Odonus indopacificus sp. nov., widely distributed throughout the Indo-Pacific basin, and Odonus indicus sp. nov., endemic to the Indian subcontinent.