Genetic diversity, population structure and demographic history of Dugesia japonica in Taihang Mountains

The freshwater planarian Dugesia japonica has become a model organism in regeneration biology and toxicology due to its powerful regeneration capability and highly chemical sensitivity. Nonetheless, little is known about its evolutionary history and demographics. Taihang Mountains is the natural boundary between the Loess Plateau and the North China Plain, and is considered as one of the important priority areas for biodiversity conservation in China. In order to figure out the genetic diversity, population structure and demographic history of D. japonica in Taihang Mountains, a study based on the mitochondrial COI from 116 individuals sampled across 20 populations has been conducted. The results showed that the 116 COI sequences yielded 32 haplotypes, including 8 shared haplotypes and 24 private ones. The overall haplotype diversity(Hd) and nucleotide diversity(π) were 0.920 and 0.083, respectively. Even though the AMOVA results suggested that the genetic variation among populations was significant(F=0.480, P<0.01), the phylogeny and haplotype network analysis based on 32 haplotypes revealed no obvious phylogeographic pattern. Furthermore, the significantly positive values of neutrality test(Tajima’s D=2.596, P<0.05; Fu’s Fs=2.769, P<0.01) together with the multimodal arrangement of mismatch distribution indicated that D. japonica in Taihang Mountains would have been undergoing population decline. We hope these findings will arouse conservation and management strategy regarding freshwater planarians and contribute to the biodiversity in the long run.