Caporale D A, Rich S M, Spielman A, Telford S R, Kocher T D
Department of Zoology, University of New Hampshire, Durham 03824, USA.
Mol Phylogenet Evol. 1995 Dec;4(4):361-5. doi: 10.1006/mpev.1995.1033.
Ticks of the genus Ixodes have recently assumed prominence because they frequently serve as vectors of important zoonoses, including Lyme disease and babesiosis. The morphological characteristics that have been used in their identification often are ambiguous and are useful solely at a particular stage of development. Here we report the DNA sequence of the mitochondrially encoded 16S rRNA gene of nine different Ixodes ticks and an outgroup from another genus, Dermacentor. The sequences readily discriminate between these ticks. Samples of I. dammini from the northeastern and upper midwestern United States differ from southeastern I. scapularis at about 2% of the nucleotides. This difference is about half that separating other members of the I. ricinus group of species, but exceeds typical levels of intraspecific variation. Two major clades exist within the I. ricinus complex. One includes I. cookei, I. hexagonus, and I. angustus. The other includes I. persulcatus, I. pacificus, I. muris, I. ricinus, I. scapularis, and I. dammini. We conclude that mtDNA sequences are useful for unravelling the systematics of these important vectors of human disease.
硬蜱属蜱虫近来备受关注，因为它们常常充当包括莱姆病和巴贝斯虫病在内的重要人畜共患病的传播媒介。用于其鉴定的形态学特征往往模棱两可，仅在特定发育阶段有用。在此，我们报告了9种不同硬蜱属蜱虫以及来自另一个属（革蜱属）的外类群的线粒体编码16S rRNA基因的DNA序列。这些序列能轻易区分这些蜱虫。来自美国东北部和中西部上游地区的达氏硬蜱样本与东南部的肩突硬蜱在约2%的核苷酸上存在差异。这种差异约为区分蓖麻硬蜱物种组其他成员差异的一半，但超过了种内变异的典型水平。蓖麻硬蜱复合体中有两个主要分支。一个包括库克硬蜱、六角硬蜱和狭腹硬蜱。另一个包括全沟硬蜱、太平洋硬蜱、鼠硬蜱、蓖麻硬蜱、肩突硬蜱和达氏硬蜱。我们得出结论，线粒体DNA序列有助于阐明这些重要人类疾病传播媒介的系统分类。
