The Genetic Diversity and the Divergence Time in Extant Primitive Mayfly, Ulmer, 1920 Using the Mitochondrial Genome

In this study, the mitochondrial (mt) genomes of (Ephemeroptera: Siphluriscidae) were evaluated in specimens collected from two sites in China: Niutou Mountain, Zhejiang Province ( NTS) and Leigong Mountain, Guizhou Province ( LGS) and were successfully sequenced. The lengths of the mt genomes of NTS and LGS were 15,904 bp (ON729390) and 15,212 bp (ON729391), respectively. However, an in-depth comparison of the two mt genomes showed significant differences between the specimens collected from the two sites. A detailed analysis of the genetic distance between NTS and LGS was undertaken to further achieve an accurate delimitation of . The genetic distance between NTS and the other three species within Siphluriscidae was a high value, above 12.2%. The two mt genomes were used to reconstruct phylogenetic relationships and estimate divergence time. The results demonstrated robust differences between NTS and LGS, which revealed that a kind of cryptic species existed. Maximum likelihood (ML) and Bayesian inference (BI) analyses produced well-supported phylogenetic trees that showed evolutionary relationships between Siphluriscidae ((( HQ875717 + MF352165) + LGS) + NTS). The most recent common ancestor (MRCA) of four species within Siphluriscidae began to diversify during the Neogene [11.80 million years ago (Mya); 95% highest posterior densities (HPD) = 6.17-19.28 Mya], and NTS was first to diverge from the branches of LGS. In short, based on mitochondrial genomes, our results showed that the specimens collected from Leigong Mountain, Guizhou Province ( LGS) belonged to , and the specimens collected from Niutou Mountain, Zhejiang Province ( NTS) were a cryptic species of .