Unexpectedly complex distribution pattern of chestnut pest Niphades castanea Chao (Coleoptera: Curculionidae) based on mtDNA and ITS markers

Niphades castanea Chao (Coleoptera: Curculionidae), an important fruit insect pest of chestnuts (Castanea spp.), could cause chestnut involucre abscission ahead of time through larvae boring and feeding basal involucres, eventually causing huge economic losses. In this research, mitochondrial (COI and COII) and nuclear (ITS1) markers were used to investigate genetic variation among 15 different geographical populations of chestnut pest N castanea. The molecular diversity of N. castanea populations revealing three main phylogenetic clusters, with cluster I specifically distributed at high elevations in the western sampling points. Mitochondrial genes indicated population expansion events, and the ITS1 marker suggested a history of population expansion. Genetic diversity differentiation was significant among populations, indicating that geographical isolation impacts genetic differentiation among these places. AMOVA analyses confirmed substantial genetic differentiation between populations. Mantel correlogram analyses revealed a significant positive correlation between genetic differentiation and altitude/geographical distance at lower elevations and ranges, which reversed to a negative correlation at higher altitudes and ranges for all markers, indicating the role of altitude and geographical distance in shaping genetic diversity in N. castanea. This study contributes to a comprehensive understanding of the distribution, genetic diversity, and evolutionary history of N. castanea in the central of China, underscoring the impact of geographical factors on its genetic structure.