The softshell turtles (Trionychidae) are one of the most widely distributed reptile groups in the world, and fossils have been found on all continents except Antarctica. The phylogenetic relationships among members of this group have been previously studied; however, disagreements regarding its taxonomy, its phylogeography and divergence times are still poorly understood as well. Here, we present a comprehensive mitogenomic study of softshell turtles. We sequenced the complete mitochondrial genomes of 10 softshell turtles, in addition to the GenBank sequence of Dogania subplana, Lissemys punctata, Trionyx triunguis, which cover all extant genera within Trionychidae except for Cyclanorbis and Cycloderma. These data were combined with other mitogenomes of turtles for phylogenetic analyses. Divergence time calibration and ancestral reconstruction were calculated using BEAST and RASP software, respectively. Our phylogenetic analyses indicate that Trionychidae is the sister taxon of Carettochelyidae, and support the monophyly of Trionychinae and Cyclanorbinae, which is consistent with morphological data and molecular analysis. Our phylogenetic analyses have established a sister taxon relationship between the Asian Rafetus and the Asian Palea + Pelodiscus + Dogania + Nilssonia + Amyda, whereas a previous study grouped the Asian Rafetus with the American Apalone. The results of divergence time estimates and area ancestral reconstruction show that extant Trionychidae originated in Asia at around 108 million years ago (MA), and radiations mainly occurred during two warm periods, namely Late Cretaceous-Early Eocene and Oligocene. By combining the estimated divergence time and the reconstructed ancestral area of softshell turtles, we determined that the dispersal of softshell turtles out of Asia may have taken three routes. Furthermore, the times of dispersal seem to be in agreement with the time of the India-Asia collision and opening of the Bering Strait, which provide evidence for the accuracy of our estimation of divergence time. Overall, the mitogenomes of this group were used to explore the origin and dispersal route of Trionychidae and have provided new insights on the evolution of this group.

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Mauremys reevesii (Gray, 1831), which belongs to Mauremys of Geoemydidae (Testudines), distributed in China, as well as Japan and Korea. Previous studies have developed several polymorphic microsatellite loci, but most of them were dinucleotide motifs. Here, we developed 15 polynucleotide-repeat microsatellite loci (including di-, tri, tetra-and pentanucleotide motifs) for M. reevesii through Restriction-site Associated DNA tags sequencing (RAD-seq). A total of 987 microsatellite loci with flanking sequences were suitable for setting primers for polymerase chain reactions (PCR). To verify the identified SSRs, 40 primer pairs were selected for PCR detection. In total, 32 primer sets produced strong PCR products matching their expected sizes, in which species amplification tests showed that 15 were polymorphic. And the number of alleles per locus ranged from 3 to 16. The observed and expected heterozygosity per locus varied from 0.3784 to 1.000 and from 0.3995 to 0.9700, respectively. The methodology of microsatellite isolation constructed in this study is not only cost-effective and time-saving in comparison to traditional approaches, but also can be served as useful tools which benefit population genetics studies and conservation management of M. reevesii.