Phylogeography of the Rice Spittle Bug (Callitettix versicolor) Implies Two Long-Term Mountain Barriers in South China

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.