Genome-wide SNP Analyses Reveal High Gene Flow of Endemic Smallscale Croaker (<i>Boesemania microlepis</i>) in the Lower Mekong Basin.

The Smallscale Croaker, <i>Boesemania microlepis</i>, is a valuable fishery resource in the Mekong River basin that lacks clear biological data to understand its basic ecology and conservation management priorities. This species is common in the southernmost floodplain of the Mekong which extends from Tonlé Sap in Cambodia to the Mekong Delta in Vietnam. This floodplain is of particular biodiversity conservation concern because of the many upstream dams that restrict water flow in an ecology that relies heavily on a flood-pulse cycle. The literature regarding the biology <i>B. microlepis</i> in this region contains conflicting ideas that populations are both highly localized and exhibit extensive migratory behavior. We used restriction-site associated DNA to test the hypothesis that localized populations exist in the southernmost floodplain of the Mekong basin. Our data indicates high connectivity among seven sites sampled in this region supporting overall panmixia. Our results suggest a potential upstream source of propagules for this floodplain and the need for further research to clarify mechanisms driving gene flow.