Zhang Gui-Hua, Yuan Zhi-Jun, Zhang Chuan-Xi, Yin Kun-Shan, Tang Mei-Jun, Guo Hua-Wei, Fu Jian-Yu, Xiao Qiang
Key Laboratory of Tea Plants Biology and Resources Utilization of Agriculture Ministry, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.
Institute of Insect Science, Zhejiang University, Hangzhou, China.
PLoS One. 2014 Jun 10;9(6):e99373. doi: 10.1371/journal.pone.0099373. eCollection 2014.
The tea geometrid (Ectropis obliqua Prout, Lepidoptera: Geometridae) is a dominant chewing insect endemic in most tea-growing areas in China. Recently some E. obliqua populations have been found to be resistant to the nucleopolyhedrovirus (EoNPV), a host-specific virus that has so far been found only in E. obliqua. Although the resistant populations are morphologically indistinguishable from susceptible populations, we conducted a nationwide collection and examined the genetic divergence in the COI region of the mtDNA in E. obliqua. Phylogenetic analyses of mtDNA in 17 populations revealed two divergent clades with genetic distance greater than 3.7% between clades and less than 0.7% within clades. Therefore, we suggest that E. obliqua falls into two distinct groups. Further inheritance analyses using reciprocal single-pair mating showed an abnormal F₁ generation with an unbalanced sex ratio and the inability to produce fertile eggs (or any eggs) through F1 self-crossing. These data revealed a potential cryptic species complex with deep divergence and reproductive isolation within E. obliqua. Uneven distribution of the groups suggests a possible geographic effect on the divergence. Future investigations will be conducted to examine whether EoNPV selection or other factors prompted the evolution of resistance.
茶尺蠖（Ectropis obliqua Prout，鳞翅目：尺蛾科）是中国大多数茶叶种植区特有的优势咀嚼式昆虫。最近发现一些茶尺蠖种群对核型多角体病毒（EoNPV）具有抗性，EoNPV是一种宿主特异性病毒，迄今为止仅在茶尺蠖中发现。尽管抗性种群在形态上与易感种群无法区分，但我们进行了全国范围的采集，并检测了茶尺蠖线粒体DNA细胞色素氧化酶亚基I（COI）区域的遗传差异。对17个种群的线粒体DNA进行系统发育分析，发现了两个不同的进化枝，进化枝之间的遗传距离大于3.7%，进化枝内部的遗传距离小于0.7%。因此，我们认为茶尺蠖可分为两个不同的群体。通过正反单对交配进行进一步的遗传分析，结果显示F₁代异常，性别比例失衡，且通过F₁自交无法产生可育卵（或任何卵）。这些数据揭示了茶尺蠖内部存在一个具有深度分化和生殖隔离的潜在隐存物种复合体。群体的不均匀分布表明地理因素可能对分化产生了影响。未来将进行调查，以研究EoNPV选择或其他因素是否促使了抗性的进化。
