Genetic Differentiation and Isolation by Distance in Mekong River Fishes With Typical Migration Patterns

Riverine fishes exhibit diverse life history traits that are the result of evolutionary processes and local adaptation. Geographical sub-populations have been influenced by complex biological and physical factors. This study evaluates the level of genetic differentiation and isolation by distance (IBD) in three Mekong fishes with typical migratory patterns. Labeo chrysophekadion (Bleeker, 1849) and Pangasius larnaudii Bocourt, 1866, are both potamodromous “white” fish, the former is considered facultative in migration, while the latter undertakes long-distance migration. Macrognathus siamensis (Günther, 1861) is a “black”, sedentary and non-migratory fish. Fish species from 7–9 natural populations were genotyped for over 800 single nucleotide polymorphisms (SNPs). Genetic differentiation indexes (FST values) revealed spatial patterns among geographical populations. Mantel tests supported strong IBD signals in both M. siamensis and L. chrysophekadion, while no IBD tendency was observed in P. larnaudii at increasing spatial scales. All three species showed a positive correlation between genetic clusters and distance in dbMEM analyses. This study highlights spatial genetic patterns and varying IBD signals corresponding to different fish migratory patterns, supporting species-specific and multi-species management strategies.