Integrative morphogenetics validates the distinctiveness of Glossogobius flavipinnis (Aurich 1938) from lake Towuti in the Wallacea biodiversity hotspot

The Malili Lakes system in Sulawesi, a unique component of the Wallacea biodiversity hotspot, harbors several endemic aquatic organisms, including species of the genus Glossogobius . Prior to this study, both morphological and molecular data on Glossogobius species were lacking from this system, particularly for Glossogobius flavipinnis (Aurich 1938), which is endemic to Lake Towuti. Hence, the present study provides the first detailed characterization of the morphological traits of G. flavipinnis , along with evidence of sexual differentiation based on multivariate Principal Component Analysis. Additional diagnostic features, such as a moderately depressed head and a first dorsal fin with black rays and distinctly bright yellow membranes, further facilitate accurate species identification and reflect adaptations to its specific ecological niche in Lake Towuti. The first mitochondrial cytochrome c oxidase subunit I sequence (mtCOI) data obtained from morphologically identified G. flavipinnis revealed its genetic distinctiveness from 19 out of the 43 other Glossogobius species included in a curated mtCOI dataset, with uncorrected p -distances ranging from 14.15% to 21.99% and Kimura two-parameter (K2P) distances ranging from 0.16 to 0.26. Conversely, the observed intra-specific genetic divergence within G. flavipinnis was low, with uncorrected p -distances of 0.2% and K2P distances of 0.002 in the current observation. Furthermore, the phylogenetic analyses using both Bayesian inference and maximum-likelihood approaches consistently supported the placement of G. flavipinnis within the genus Glossogobius . Collectively, this investigation integrates morphological and molecular evidence derived from well-curated voucher specimens to confirm the species identity of the endemic G. flavipinnis . However, the limited sampling and genetic dataset may not adequately capture the complete population structure across the species’ entire geographic range. This study also underscores the need for similar integrative assessments of other endemic Glossogobius species and freshwater taxa within the Malili Lakes system.