Rees David J, Dioli Maurizio, Kirkendall Lawrence R
Department of Zoology, University of Bergen, Allégaten 41, 5007 Bergen, Norway.
Mol Phylogenet Evol. 2003 Apr;27(1):131-42. doi: 10.1016/s1055-7903(02)00374-3.
The role of natural hybridization and introgression as part of the evolutionary process is of increasing interest to zoologists, particularly as more examples of gene exchange among species are identified. We present mitochondrial and nuclear sequence data for Hyalomma dromedarii, Hyalomma truncatum, and Hyalomma marginatum rufipes (Acari: Ixodidae) collected from one-humped camels in Ethiopia. These species are well differentiated morphologically and genetically; sequence data from the mitochondrial DNA (mtDNA) cytochrome oxidase I gene indicates 10-14% divergence between the species. However, incongruence between morphology and the mtDNA phylogeny was observed, with multiple individuals of H. dromedarii and H. truncatum present on the same mtDNA lineage as H. marginatum rufipes. Thus, individuals with morphology of H. dromedarii and H. truncatum are indistinguishable from H. marginatum rufipes on the basis of mtDNA. Multiple copies of ITS-2 were subsequently cloned and sequenced for a subset of individuals from the mtDNA phylogeny, representing both 'normal' and 'putative hybrid' individuals. Very low sequence divergence (0.3%) was observed within 'normal' individuals of both H. dromedarii and H. truncatum relative to the 'putative hybrid' individuals (6 and 2.7%, respectively). The pattern of intra-individual variation in ITS-2 within 'putative hybrid' individuals, particularly in H. dromedarii, strongly suggests that gene flow has occurred among these Hyalomma species, but no indication of this is given by the morphology of the individuals.
自然杂交和基因渗入作为进化过程的一部分，其作用越来越受到动物学家的关注，特别是随着物种间基因交换的更多实例被发现。我们展示了从埃塞俄比亚单峰骆驼身上采集的埃及璃眼蜱、截形璃眼蜱和边缘璃眼蜱（蜱螨目：硬蜱科）的线粒体和核序列数据。这些物种在形态和基因上有明显差异；线粒体DNA（mtDNA）细胞色素氧化酶I基因的序列数据表明，这些物种之间的差异为10 - 14%。然而，观察到形态与mtDNA系统发育之间存在不一致，埃及璃眼蜱和截形璃眼蜱的多个个体与边缘璃眼蜱存在于同一mtDNA谱系上。因此，基于mtDNA，具有埃及璃眼蜱和截形璃眼蜱形态的个体与边缘璃眼蜱无法区分。随后，对mtDNA系统发育中的一部分个体（代表“正常”和“假定杂交”个体）的ITS - 2进行了多份克隆和测序。相对于“假定杂交”个体（分别为6%和2.7%），在埃及璃眼蜱和截形璃眼蜱的“正常”个体中观察到非常低的序列差异（0.3%）。“假定杂交”个体，特别是埃及璃眼蜱个体内ITS - 2的个体内变异模式强烈表明，这些璃眼蜱物种之间发生了基因流动，但个体形态并未显示出这种迹象。
