How did the white-spotted flower chafer (Protaetia brevitarsis) come to Xinjiang?

Protaetia brevitarsis (Lewis, 1879) is a serious agricultural and forestry pest. Since first report in Xinjiang (XJ), China in 2001, it has rapidly spread. This study explored the phylogeographic structure of Chinese P. brevitarsis as well as the origin and dispersal route of the XJ population using COI and EF-1α gene-based analysis, geometric morphometrics, and the optimized maximum entropy (MaxEnt) model. The results indicated Chinese populations exhibit high genetic diversity. Spatiotemporal reconstruction of the geographic dispersal indicated P. brevitarsis initially moved from its origin in the Huang-Huai region (HH) to XJ through the Hexi Corridor during the late Pleistocene, approximately 0.135 million years ago (Ma). Before 0.02 Ma, reciprocal active dispersal events occurred between XJ population and others, leading to the formation of the current phylogeographic pattern. This aligns with the demographic history, P. brevitarsis experienced continuous and rapid population expansion from 0.075 to 0.006 Ma. Based on the Procrustes distance cluster analysis of shape variation of the white spots on the elytra, the populations of HH, XJ, North China, and SGN (including Shaanxi, Gansu, and Ningxia regions) exhibit high morphological similarity, supporting the molecular research that these geographic populations are closely related. MaxEnt indicated suitable habitats in western Inner Mongolia during the Last Interglacial and the Hexi Corridor during the Last Glacial Maximum, facilitating dispersal from eastern China to XJ. During the Mid-Holocene and the current period, the corridor for active dispersion cut off. Gene flow between XJ population and eastern populations may be attributed to passive dispersion resulting from agricultural trade. These results alter previous understanding of the origin and evolutionary history in XJ, and provide scientific evidence for differentiated control measures for different geographic populations of P. brevitarsis.