Kovalev Sergey Y, Mikhaylishcheva Maria S, Mukhacheva Tatyana A
Laboratory of Molecular Genetics, Department of Biology, Ural Federal University, Lenin Avenue 51, Yekaterinburg 620000, Russia.
Laboratory of Molecular Genetics, Department of Biology, Ural Federal University, Lenin Avenue 51, Yekaterinburg 620000, Russia.
Infect Genet Evol. 2015 Jun;32:388-95. doi: 10.1016/j.meegid.2015.04.003. Epub 2015 Apr 6.
Hybridization of ticks of the genus Ixodes has been described for several species under laboratory conditions although no molecular genetics evidence confirming interspecific hybridization in nature is available. We have designed a real time PCR targeted on nuclear (ITS2) and mitochondrial (cox1) markers to accurately identify tick species and to detect interspecific hybrids of Ixodes persulcatus and Ixodes pavlovskyi in their sympatric populations in Western Siberia. A survey of 783 individual ticks from a suburb of Tomsk showed that 44.2% of ticks belong to I. pavlovskyi species and 55.8% to I. persulcatus, based on the mtDNA data. Results obtained with the nuclear marker were not consistent, indicating that approximately 10% of the ticks were hybrids and about 5% revealed mtDNA introgression. Both hybridization and introgression have been shown to occur bidirectionally but more efficiently in the mating pair female I. pavlovskyi×male I. persulcatus than vice versa. The existence of the first generation hybrids and backcrosses challenges the existing view about effective reproductive barriers between I. pavlovskyi and I. persulcatus. While using only mitochondrial markers can lead to errors in determining tick species, we propose to use nuclear or both markers instead. The results obtained in the present paper and published earlier suggest that hybridization between closely related tick species in their sympatric zones is common rather than exceptional. The role of hybrid populations of vectors in the evolution of transmitted pathogens is also discussed.
在实验室条件下，已描述了硬蜱属几种蜱的杂交情况，尽管尚无分子遗传学证据证实自然界中存在种间杂交。我们设计了一种针对核标记（ITS2）和线粒体标记（cox1）的实时PCR方法，以准确鉴定蜱的种类，并检测西西伯利亚同域分布种群中的全沟硬蜱和巴甫洛夫硬蜱的种间杂交种。对托木斯克郊区的783只蜱个体进行的调查显示，根据线粒体DNA数据，44.2%的蜱属于巴甫洛夫硬蜱，55.8%属于全沟硬蜱。核标记获得的结果不一致，表明约10%的蜱为杂交种，约5%显示出线粒体DNA渐渗。已证明杂交和渐渗都是双向发生的，但在巴甫洛夫硬蜱雌蜱×全沟硬蜱雄蜱的交配组合中更有效，反之则不然。第一代杂交种和回交种的存在挑战了关于巴甫洛夫硬蜱和全沟硬蜱之间有效生殖屏障的现有观点。虽然仅使用线粒体标记可能会导致蜱种鉴定错误，但我们建议使用核标记或两者兼用。本文及先前发表的结果表明，在同域分布区域中，亲缘关系密切的蜱种之间的杂交很常见而非例外。还讨论了媒介杂交种群在传播病原体进化中的作用。
