Multilocus evidence provides insight into the demographic history and asymmetrical gene flow between and (Lepidoptera: Crambidae) in the Yili area, Xinjiang, China.

Tianshan Mountains provide a model for studying biological evolution and speciation. Here we assess the evolutionary history of (ACB) and (ECB), which are sympatric in the Yili River Valley in Xinjiang, China.Our study is based on the historical gene flow analyses of two species by using three mitochondrial DNA (mtDNA, , , ) and four nuclear DNA (nuDNA, , , , ) markers obtained from representatives of HC (Huocheng), YN (Yining), XY (Xinyuan), and MNS (Manasi).Our results reveal that there is an asymmetrical gene flow pattern between the four populations. The population migratory pathways between these different populations show inflow into HC and YN, outflow from XY, and that MNS maintained a flow balance. Bayesian divergence time dating based on the gene suggests that the genetic divergence between the two species in this area may have occurred in Holocene at 0.008 Mya. Neutrality tests (Tajima's , Fu's ), and mismatch distribution test results suggest that population expansion events may not have occurred in the recent past. The demographic history and gene flow pattern between ACB and ECB may follow the "mountain isolation" hypothesis. The ML and BI trees of the mtDNA haplotype dataset show that ECB haplotypes are grouped together in a distinct clade and are clearly separate from ACB haplotypes. However, the geographical pattern of haplotype distribution is less clear for both ACB and ECB, supporting that there has been frequent gene flow among the geographic populations in the Tianshan Mountains.These findings indicate that the Tianshan Mountains are less likely a barrier to gene flow of the two species.