狄斯瓦螨种群遗传结构及杀螨剂选择压力下的基因流动

The Varroa destructor is an ectoparasitic mite and most important biotic threat to honey bee worldwide. Increasingly severe damage to Apis mellifera has been reported in recent years, the main reasons were resistance to pyrethroids acaricide and gene flow among different V. destructor populations. So far, the information of population genetics and gene flow patterns in relation to acaricide selection pressure among different geographical populations has not been studied in the country. Basing on our primary work, we will collect V. destructor samples in different honey bee feeding regions throughout China and the resistance level of different V. destructor populations to tau-fluvalinate were tested by the method of residual films in glass tube. Microsatellite markers were used to investigate the genetic diversity, genetic structure and the mode of gene flow as well as the extent of the genetic differentiation at the interspecific and intraspecific levels of populations, and explore the dispersal patterns of this mite in China. Also combined with resistance level and voltage-gated sodium channel genes, the study will evaluate the relationship among gene flow, insecticide susceptibility and resistance genes, and how the acaricide selection pressure affects the gene flow pattern and micro-evolution of V. destructors population with different genetic background. The results not only deepen the understanding of population evolution and population genetics of V. destructor and provide invaluable information on ecologically mechanism and genetic variability of V. destructor in theory level, but also can be used for sustainable control and resistance management of V. destructor in China.

狄斯瓦螨是一种在世界范围内广泛发生并造成严重经济损失的蜜蜂外寄生螨。近些年，该螨在我国的危害逐年加重并成为我国养蜂业的头号劲敌，这与其对杀螨剂抗药性上升和不同种群间基因交流密切相关。基于已有的研究基础上，本项目拟在全国范围内采集狄斯瓦螨样本，测定各地理种群对常用杀螨剂的抗性水平；利用微卫星标记，解析我国狄斯瓦螨种群遗传多样性和遗传结构变化规律、种群间遗传分化程度和基因交流模式以及狄斯瓦螨在我国的扩散传播途径；同时结合各地理种群的抗性水平和钠离子通道抗性突变情况，分析狄斯瓦螨抗药性水平和抗性基因的种群差异与种群间基因交流的相互关系及影响种群遗传分化机制，探讨杀螨剂选择压力下的种群间基因交流与微进化。研究结果将在理论上深化对狄斯瓦螨种群遗传结构的认识，丰富遗传变异和抗药性的研究内容；在实践上为狄斯瓦螨抗性治理和制定科学防控策略提供理论依据。

狄斯瓦螨是蜜蜂重要外寄生螨，稳定的遗传结构、频繁的基因交流及对杀螨剂抗药性是其对我国养蜂业危害逐年加重的主要原因。本研究通过筛选得到5个稳定扩增且多态性较好的狄斯瓦螨微卫星位点，对我国狄斯瓦螨不同地理种群的遗传多样性、遗传分化和遗传结构进行研究，并检测各样本的钠离子通道基因突变位点。遗传多样性结果表明，不同狄斯瓦螨种群间存在一定程度的遗传变异，其中多数种群的期望杂合度均低于观测杂合度，且近交系数均小于0，表明这些种群杂合子过剩且显著偏离哈迪-温伯格平衡。遗传结构分析表明，狄斯瓦螨种群间中存在显著的遗传结构，20个地理种群被划分为3个类群，且不同种群间存在显著的遗传分化和基因交流；分子方差分析表明，大多数的遗传变异来自狄斯瓦螨种群内，且不同狄斯瓦螨种群间的遗传多样性和遗传结构的差异与其所在地理位置、生态条件以及生殖方式等种群生物学特性及防治措施有关。对不同狄斯瓦螨种群的钠离子通道突变检测发现，含有钠离子通道突变个体多分布在我国南方种群中，这可能是由于我国南方地区作为蜜蜂越冬和春繁的地点，蜂群管理过程中持续用药导致抗药性的产生，同时随着转场放蜂等人为因素的作用下，使得抗性基因在不同地理种群中传播。本研究结果对于阐明我国狄斯瓦螨种群的生态适应和成灾机制及抗性发展趋势，为制定符合我国狄斯瓦螨遗传结构和基因流动特点的综合治理策略具有重要的指导意义。