Animal mitochondrial genes continue to provide an efficient and inexpensive assessment of genetic diversity. However, which mitochondrial genes should be selected to best estimate species phylogeny and population genealogy remains uncertain for most under-sampled taxa. We analysed four complete mitochondrial genomes of sibling species of Euphaea damselflies, E. decorata, E. ornata, E. formosa and E. yayeyamana (Insecta, Odonata, Euphaeidae), to examine the patterns of selection and to evaluate the phylogenetic utility of the mitochondrial genes compared with nuclear genes. The results indicated that mitochondrial protein-coding nad2 (NADH dehydrogenase subunit 2) and noncoding A + T-rich (control region) genes have the highest mutation rates and more phylogenetic utility [higher parsimony-informative sites; higher (the shape parameter of gamma distribution); lower rates of heterogeneity among sites; and higher relative substitution rates] than all the other mitochondrial and nuclear genes analysed. In contrast, the animal DNA barcoding gene cytochrome c oxidase subunit 1 (cox1) had average values for all estimated parameters of phylogenetic performance and was sometimes outperformed by other mitochondrial genes. The majority of the mitochondrial and nuclear genes in Euphaea damselflies have experienced frequent purifying selection, except for two cases of potential positive selection in NADH dehydrogenase subunit 3 (nad3) and elongation factor 1 (EF1 ), and all mitochondrial genes had experienced stronger purifying selection than nuclear genes. Our findings indicated that mitochondrial nad2 and the A + T-rich region should be selected to provide efficient and high-resolution phylogenetic markers for damselflies at the species and population level.

South China is a region of remarkable topographic complexity. However, the impact of climate fluctuations in the Pleistocene on the local fauna and especially insects has not been extensively studied. We integrated mitochondrial DNA (mtDNA) and microsatellite data of the rice spittle bug, Callitettix versicolor, to determine the genetic structure, potential biogeographic barriers, and historical demography of this species. The mtDNA data revealed two distinct lineages (Western and Eastern) congruent with the geographically separated western and eastern sub-regions of the Hengduan Mountains. The Eastern lineage was subdivided into two sub-lineages, E1 and E2, congruent with the geographically separated northern and southern sub-regions of the Dabie Mountains. E2 was further subdivided into two sub-groups, E2-1 and E2-2, with a hybrid zone (Guizhou and Hunan Provinces) in which their areas were contiguous. The genetic structures constructed using mtDNA were corroborated by four clusters (G1-G4) of microsatellite data. The populations of each cluster were nearly consistent with a sub-lineage of the mtDNA gene tree (G1-G4 corresponded to the Western, E1, E2-2 and E2-1 lineages, respectively). The divergence time estimated between the Western and Eastern lineages was 1.17 (0.50-2.37) to 0.89 (0.39-1.78) Mya, indicating that the lineages diversified on both geographic and temporal scales. The historical demography of the Eastern lineage showed continuous population growth after the Last Interglacial (LIG) and a stable population during the Last Glacial Maximum (LGM) period. However, the Western lineage remained largely unchanged during the LIG and LGM periods. This suggests that the historical demography of C. versicolor is probably related not only to the paleoclimate of South China, but also to the geological restriction and specific habitat preferences of species.

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