McLain D K, Wesson D M, Oliver J H, Collins F H
Department of Biology, Georgia Southern University, Statesboro 30460, USA.
J Med Entomol. 1995 May;32(3):353-60. doi: 10.1093/jmedent/32.3.353.
The base sequence of the internal transcribed spacer 1 (ITS 1) of ribosomal DNA of the tick Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) was determined to assess genetic divergence between populations along the eastern (Atlantic) seaboard of the United States. Twenty sequences were obtained from localities down the eastern margin of the species's range: 10 from the southeast (Georgia and Florida), seven from the middle east (North Carolina, Maryland), and three from the northeast (Massachusetts, New Jersey, New York). Both the neighbor-joining and parsimony methods cluster most of the southeastern sequences together and most of the middle eastern sequences together but fail to cluster those from the northeast. In addition, an F ratio test revealed significant between-region sequence variation. Thus, there appears to be genetic structuring on at least a macrogeographic scale. Only 23% (SEM = 6.4%) of the sequence variation occurs between regions, with the vast majority of variation, 77% (SEM = 6.4%), being within region. These data, plus other published data, indicate that I. scapularis constitutes a single species. However, the pattern of variation is consistent with restricted gene flow between regions or, alternatively, with recent introgression between northern and southern types in the middle-eastern part of the species's range.
测定肩突硬蜱（Ixodes scapularis Say，即达氏硬蜱I. dammini Spielman、Clifford、Piesman和Corwin）核糖体DNA的内转录间隔区1（ITS 1）的碱基序列，以评估美国东部（大西洋）沿海各群体之间的遗传差异。从该物种分布范围东缘的不同地点获得了20个序列：10个来自东南部（佐治亚州和佛罗里达州），7个来自中东地区（北卡罗来纳州、马里兰州），3个来自东北部（马萨诸塞州、新泽西州、纽约州）。邻接法和简约法都将大多数东南部序列聚在一起，大多数中东序列也聚在一起，但未能将来自东北部的序列聚在一起。此外，F比率检验显示区域间序列存在显著差异。因此，至少在宏观地理尺度上似乎存在遗传结构。只有23%（标准误=6.4%）的序列变异发生在区域间，绝大多数变异（77%，标准误=6.4%）发生在区域内。这些数据，加上其他已发表的数据，表明肩突硬蜱构成一个单一物种。然而，变异模式与区域间有限的基因流动一致，或者与该物种分布范围中东地区南北类型之间最近的基因渗入一致。
