Origin and Expansion of the Yunnan Shoot Borer, Tomicus yunnanensis (Coleoptera: Scolytinae): A Mixture of Historical Natural Expansion and Contemporary Human-Mediated Relocation

PLOS ONE, Dec 2019

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. Migration analysis also showed a certain degree of recent expansion from southwestern Sichuan to eastern Yunnan. Our findings implied that T. yunnanensis underwent both historical expansion and recent dispersal. The historical expansion may relate to the oscillation of regional climate due to glacial and interglacial periods in the Pleistocene, while human-mediated transportation of pine-wood material might have assisted the relocation and establishment of this pest in novel habitats.

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Origin and Expansion of the Yunnan Shoot Borer, Tomicus yunnanensis (Coleoptera: Scolytinae): A Mixture of Historical Natural Expansion and Contemporary Human-Mediated Relocation

Tomicus yunnanensis (Coleoptera: Scolytinae): A Mixture of Historical Natural Expansion and Contemporary Human-Mediated Relocation. PLoS ONE 9(11): e111940. doi:10.1371/journal.pone.0111940 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 0 Shao-ji Hu 0 Xue-yu Ma 0 Jin-min Chen 0 Qing-qing Li 0 Hui Ye 0 Wolfgang Arthofer, University of Innsbruck, Austria 0 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 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. Migration analysis also showed a certain degree of recent expansion from southwestern Sichuan to eastern Yunnan. Our findings implied that T. yunnanensis underwent both historical expansion and recent dispersal. The historical expansion may relate to the oscillation of regional climate due to glacial and interglacial periods in the Pleistocene, while human-mediated transportation of pine-wood material might have assisted the relocation and establishment of this pest in novel habitats. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All original DNA haplotype data files are available from the NCBI GenBank database JX448430JX448477 (H1H47 and T. armandii) and KC986943KC986953 (H48H57 and T. piniperda). Funding: The present study was supported by the National Natural Science Foundation of China (31360183), the Applied Basic Research Foundation of Yunnan Province (2013FA055), and the Applied Basic Research Foundation for Young Scientists of Yunnan Province (2014FD025). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. The Yunnan shoot borer, Tomicus yunnanensis Kirkendall & Faccoli (Coleoptera: Curculionidae: Scolytinae), is one of the most aggressive pest species in genus Tomicus, which has caused serious annual damage in up to 20,000 ha of the Yunnan pine, Pinus yunnanensis Franchet, since the major outbreak in southwestern China in the 1980s [13]. For the past two decades, T. yunnanensis has been confused with T. piniperda Linnaeus due to morphological resemblance, but genetic comparison between the southwestern Chinese population and the Eurasian T. piniperda suggested that the former should be treated as a previously undescribed Tomicus species [4]. Based on these findings, Kirkendall et al. (2008) analyzed the morphological characters of all known Tomicus species and described this beetle for the first time [5]. The Yunnan pine, P. yunnanensis, is the only known host of T. yunnanensis to date [3]. This pine is the most important silvicultural tree in southwestern China due to its high tolerance to drought [6]. Therefore, the continuous infestation and constant outbreak of T. yunnanensis has brought severe damage to the environment in this region [7]. T. yunnanensis is endemic to southwestern China, and its distribution range is highly overlapped with the Yunnan pine [3]. The first population outbreaks of this beetle were recorded in the Central-Yunnan altiplano, and then in northern, western, (...truncated)


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Jun Lü, Shao-ji Hu, Xue-yu Ma, Jin-min Chen, Qing-qing Li, Hui Ye. Origin and Expansion of the Yunnan Shoot Borer, Tomicus yunnanensis (Coleoptera: Scolytinae): A Mixture of Historical Natural Expansion and Contemporary Human-Mediated Relocation, PLOS ONE, 2014, 11, DOI: 10.1371/journal.pone.0111940