Vol. 6 No. 1 (2026): SRAI Journal of Linguistics and Social Sciences

Mol Ecol. 2026 Jun;35(11):e70414. doi: 10.1111/mec.70414. Ancient and Recent Riverine Gene Flow Contributed to the Adaptive Radiation of Sailfin Silversides in Wallace's Dreampond. De Keyzer ELR(1), Herder F, Böhne A, Jiménez FC, Burskaia V, Kukowka S, Tracey A, Denton AL, Oatley G(4); Wellcome Sanger Institute Tree of Life programme(5); Wellcome Sanger Institute Scientific Operations: DNA Pipelines Collective(6); Tree of Life Core Informatics Collective(7); Mokodongan DF, Wowor D, Svardal H(1)(9).(2)Aquatic Macrofauna Biodiversity and Conservation Research Group, Hasanuddin University, Makassar, Indonesia. (3)Leibniz-Institute for the Analysis of Biodiversity Change (LIB), Museum Koenig Bonn, Bonn, Germany. (4)Wellcome Sanger Institute, Hinxton, UK. (5)Members: https://doi.org/10.5281/zenodo.4783585, Hinxton, UK. (6)Members: https://doi.org/10.5281/zenodo.4790455, Hinxton, UK. (7)Members: https://doi.org/10.5281/zenodo.7116866, Hinxton, UK. (8)Museum Zoologicum Bogoriense, Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN), Cibinong, Indonesia. (9)Naturalis Biodiversity Center, Leiden, the Netherlands. While adaptive radiations significantly contribute to the world's biodiversity, much is unknown about the genetic and ecological factors underlying these rapid successions of speciation. It has been suggested that hybridisation can facilitate the speciation process by generating genetic diversity on which diversifying selection can act. Sailfin silverside fishes (Telmatherinidae) in the Malili Lakes system in Sulawesi have diversified within the last 2 million years. To establish a phylogenetic framework and investigate the presence of hybridisation in this radiation, we assembled and annotated a chromosome-scale reference genome of the riverine sailfin silverside Telmatherina bonti and generated whole genome sequences of all species of Telmatherina in Lake Matano, South Sulawesi, Indonesia, one of the world's oldest and deepest lakes. We reconstructed the phylogenetic relationships and inferred past and ongoing introgression patterns. Genome-wide tests confirmed two monophyletic clades, sharpfins and roundfins. However, within clades, we found mismatches between morphology-based taxonomic assignments and genome-wide genetic relationships. We found signs of both old and ongoing introgression between river-dwelling T. bonti and the lacustrine sharpfin group, as shown in elevated D-statistic, f4-ratio and f-branch statistic. Levels of excess allele sharing between riverine species and the three most common lacustrine species declined with increasing distance from the river-inlet, indicating ongoing introgression at the lake-river interface. This combination of past and ongoing hybridisation in a radiating species flock makes Lake Matano Telmatherina a particularly valuable system to study fundamental mechanisms driving rapid speciation under genomic exchange. The phylogenomic framework elaborated in this study provides the foundation for studies of the processes shaping this charismatic radiation. © 2026 The Author(s). Molecular Ecology published by John Wiley & Sons Ltd. DOI: 10.1111/mec.70414 PMCID: PMC13253165 PMID: 42270437 [Indexed for MEDLINE] Conflict of interest statement: The authors declare no conflicts of interest.