Origin and Expansion of the Yunnan Shoot Borer, Tomicus Yunnanensis
Origin and Expansion of the Yunnan Shoot Borer, Tomicus yunnanensis (Coleoptera: Scolytinae): A Mixture of Historical Natural Expansion and Contemporary Human-Mediated Relocation Jun Lu¨ 1,2., Shao-ji Hu1,2., Xue-yu Ma1,3, Jin-min Chen4, Qing-qing Li5, Hui Ye1,2* 1 Laboratory of Biological Invasion and Ecosecurity, Yunnan University, Kunming, 650091, China, 2 Yunnan Key Laboratory of International Rivers and Transboundary Eco- security, Yunnan University, Kunming, 650091, China, 3 School of Mathematics and Computer Science, Yunnan University of Nationalities, Kunming, 650031, China, 4 Laboratory for Conservation and Utilization of Bio-resources, Yunnan University, Kunming, 650091, China, 5 Life Science College, Yunnan Normal University, Kunming, 650092, China Abstract The Yunnan shoot borer, Tomicus yunnanensis, is a recently-discovered, aggressive pest of the Yunnan pine stands in southwestern China. Despite many bionomics studies and massive controlling efforts, research on its population genetics is extremely limited. The present study, aimed at investigating the origin and dispersal of this important forestry pest, analyzed the population genetic structure and demographic history using a mitochondrial cox1 gene fragment. Our results showed that T. yunnanensis most likely originated from the Central-Yunnan Altiplano, and the divergence time analysis placed the origin approximately 0.72 million-years ago. Host separation and specialization might have caused the speciation of T. yunnanensis. Genetic structure analyses identified two population groups, with six populations near the origin area forming one group and the remaining six populations from western and eastern Yunnan and southwestern Sichuan comprising the other. Divergence time analysis placed the split of the two groups at approximately 0.60 million-years ago, and haplotype phylogenetic tree, network, as well as migration rate suggested that populations of the latter group were established via a small number of individuals from the former one.
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