Differentiated or not? An assessment of current knowledge of genetic structure of Sousa chinensis in China

Estimating the degree of isolation or gene flow is central to understanding population dynamics and conservation. In this study, we used both mitochondrial and nuclear markers to investigate the genetic structure of Indo-Pacific humpback dolphins (genus Sousa) in China. Contrary to previous photo-identification and genetic studies, we found no evidence for population genetic structure or inter-population gene flow across the geographical scale examined. Significant inbreeding, which seems to support genetic isolation to some extent, was within expectation as a result of low genetic diversity in a random-mating system. Overall, the Indo-Pacific humpback dolphins in China were characterized by low genetic diversity on both maternal and bi-parental markers. While significant steps have been taken towards implementing marine reserves, our study highlights the critical need for fine-scale genetic and ecological monitoring programs and a coordinated approach to secure the survival of Indo-Pacific humpback dolphins in Chinese waters.