Sungirai Marvelous, Baron Samantha, Van der Merwe Nicolaas A, Moyo Doreen Zandile, De Clercq Patrick, Maritz-Olivier Christine, Madder Maxime
Unit of Veterinary Entomology, Institute of Tropical Medicine, Dept of Biomedical Sciences, Nationalestraat 122, Antwerp 2000, Belgium; Department of Livestock and Wildlife Management, Midlands State University, 1 Senga Road, P. Bag 9055 Gweru, Zimbabwe.
Department of Genetics, University of Pretoria, 0083, Pretoria, South Africa.
Acta Trop. 2018 Apr;180:42-46. doi: 10.1016/j.actatropica.2018.01.003. Epub 2018 Jan 8.
Recently there was an expansion in the geographic range of Rhipicephalus microplus in Zimbabwe. In order to understand gene flow patterns and population structure in this highly invasive and adaptable cattle tick, a population genetics study was carried out. Eighty-seven R. microplus tick samples drawn from 5 distinct populations were genotyped using eight polymorphic microsatellite loci. Genetic diversity (H) was high (0.755-0.802) in all the populations, suggesting high levels of gene flow with 97% of genetic variation found within populations and 3% amongst populations. No isolation by distance was observed with low but significant genetic differentiation amongst the populations (0-0.076). Most of the sampled individuals had admixed genetic backgrounds, except for those from Matabeleland North whose genetic makeup appeared different from the rest. Rhipicephalus microplus was recently recorded in this area and the environmental conditions do not support survival of the tick there. These results confirm recent range expansion of the tick and the lowest genetic diversity recorded in the Matabeleland North population is suggestive of a founder effect, which may lead to genetic drift. Generally, the very low levels of genetic differentiation amongst the populations could be a result of the frequent movement of livestock from one area to another, which will have implications for disease control. This study offers further opportunities to study evolutionary adaptation of R. microplus in Zimbabwe and southern Africa.
最近，微小扇头蜱在津巴布韦的地理分布范围有所扩大。为了解这种极具入侵性和适应性的牛蜱的基因流动模式和种群结构，开展了一项种群遗传学研究。使用8个多态性微卫星位点对从5个不同种群采集的87个微小扇头蜱样本进行了基因分型。所有种群的遗传多样性（H）都很高（0.755 - 0.802），这表明基因流动水平较高，97%的遗传变异存在于种群内部，3%存在于种群之间。未观察到距离隔离现象，种群间的遗传分化程度较低但显著（0 - 0.076）。除了来自北马塔贝莱兰的个体，大多数采样个体都有混合的遗传背景，北马塔贝莱兰个体的基因组成似乎与其他个体不同。微小扇头蜱最近在该地区被记录到，而当地的环境条件并不支持该蜱在那里生存。这些结果证实了该蜱最近的分布范围扩张，北马塔贝莱兰种群记录到的最低遗传多样性表明存在奠基者效应，这可能导致遗传漂变。总体而言，种群间极低水平的遗传分化可能是牲畜频繁从一个地区转移到另一个地区的结果，这将对疾病控制产生影响。这项研究为研究微小扇头蜱在津巴布韦和南部非洲的进化适应性提供了更多机会。
