Species diversity and evolutionary relationships of freshwater fish in the Central Highlands, Vietnam, based on molecular markers

Abstract

The Central Highlands, encompassing five provinces before the administrative reorganisation, is traversed by the Se San and Srepok rivers, known as two main branches of the transboundary 3S river system (Se San - Se Kong - Srepok). There are 240 and 133 fish species recorded in the Srepok and Sesan rivers, respectively. This study aims to investigate the diversity and phylogenetic relationships of freshwater fish in the Central Highlands. The samples were collected at Se San and Srepok rivers in Dak Lak, Dak Nong, Gia Lai and Kon Tum provinces. Based on morphological characteristics, 68 species have been identified, including: Order Cypriniformes (7 families, 28 genera, 37 species); Order Siluriformes (6 families, 10 genera, 17 species); Order Osteoglossiformes (1 family, 2 genera, 2 species); Order Anabantiformes (4 families, 5 genera, 8 species); Order Gobiiformes (1 family, 2 genera, 2 species); Order Cichliformes (both of 1 species) and Ovalentaria series (1 species). The phylogenetic tree was constructed based on four different Cytochrome b (cytb) gene mitochondrial DNA datasets using the Neighbor-Joining and Maximum Likelihood approaches, with Batrachomoeus trispinosus used as the outgroup. The phylogram was divided into two main lineages, lineages 1 included Cypriniformes, Siluriformes, Osteoglossiformes, and Gobiiformes; while lineages 2 included Anabantiformes,
Cichliformes, and series Ovalentaria (all previously belong to the order Perciformes). The monophyletic and polyphyletic status at different taxonomic levels (order, family, and genus) were discussed and compared. These findings provide genetic data on fish diversity in the Mekong river, serving as a scientific basis for conservation and management of freshwater fishery resources.