Oliver J H, Owsley M R, Hutcheson H J, James A M, Chen C, Irby W S, Dotson E M, McLain D K
Institute of Arthropodology and Parasitology, Georgia Southern University, Statesboro 30460.
J Med Entomol. 1993 Jan;30(1):54-63. doi: 10.1093/jmedent/30.1.54.
Reciprocal crosses between Ixodes dammini Spielman, Clifford, Piesman & Corwin from Massachusetts and Ixodes scapularis Say from Georgia produced offspring through the F3 generation when the experiment was discontinued. Reciprocal I. dammini x Ixodes pacificus Cooley & Kohls (California) and I. scapularis x I. pacificus crosses produced F1 progeny; however, all progeny were sterile. Assortative mating experiments between I. dammini and I. scapularis indicated that males and females of both species mated with the opposite sex of heterospecific or conspecific ticks when there was a choice. Conventional discriminant analysis of morphometric measurements of ticks from Georgia, North Carolina, Maryland, Massachusetts, and two populations of F1 hybrids indicated that there were recognizable differences. However, size-free (sheared) discriminant analysis indicated that these differences were largely size-dependent, with much overlap of the four eastern and two hybrid populations but no overlap with I. pacificus from California. Analysis of chromosomes (morphology and C band) indicated no differences between the Georgia and Massachusetts populations but showed a difference between them and the California population of I. pacificus. Analysis of isozymes showed that the genetic identity value for the Georgia and Massachusetts populations was within the normal range for conspecific populations, whereas the California population indicated congeneric but not conspecific relatedness to the Georgia and Massachusetts populations. Life cycle data collected under similar laboratory conditions showed no differences in length of feeding and molting periods among Georgia, Massachusetts, and California populations. These data and results of the work of other authors on tick host preferences and vector competence indicate that I. dammini is not a valid species separate from I. scapularis. Because the name Ixodes scapularis Say, 1821, has priority over the name Ixodes dammini Spielman, Clifford, Piesman & Corwin, 1979, I. dammini is relegated to a junior subjective synonym of I. scapularis (based on Article 23 of the International Code of Zoological Nomenclature).
将来自马萨诸塞州的达氏硬蜱（Ixodes dammini Spielman、Clifford、Piesman & Corwin）与来自佐治亚州的肩突硬蜱（Ixodes scapularis Say）进行正反交，当实验终止时，杂交后代已繁衍至F3代。达氏硬蜱与太平洋硬蜱（Ixodes pacificus Cooley & Kohls，加利福尼亚州）以及肩突硬蜱与太平洋硬蜱的正反交均产生了F1代后代；然而，所有后代均不育。对达氏硬蜱和肩突硬蜱进行的选型交配实验表明，在有选择的情况下，这两个物种的雄性和雌性都会与异种或同种蜱的异性进行交配。对来自佐治亚州、北卡罗来纳州、马里兰州、马萨诸塞州的蜱以及两个F1代杂交种群的形态测量数据进行常规判别分析，结果表明存在可识别的差异。然而，无尺寸（剪去）判别分析表明，这些差异很大程度上取决于尺寸，四个东部种群和两个杂交种群之间有大量重叠，但与来自加利福尼亚州的太平洋硬蜱没有重叠。染色体分析（形态和C带）表明，佐治亚州和马萨诸塞州的种群之间没有差异，但它们与加利福尼亚州的太平洋硬蜱种群存在差异。同工酶分析表明，佐治亚州和马萨诸塞州种群的遗传同一性值在同种种群的正常范围内，而加利福尼亚州的种群表明与佐治亚州和马萨诸塞州的种群属于同属但不同种的关系。在相似实验室条件下收集的生命周期数据表明，佐治亚州、马萨诸塞州和加利福尼亚州的种群在取食期和蜕皮期的长度上没有差异。这些数据以及其他作者关于蜱宿主偏好和传播能力的研究结果表明，达氏硬蜱并非与肩突硬蜱不同的有效物种。由于1821年的肩突硬蜱（Ixodes scapularis Say）这个名称优先于1979年的达氏硬蜱（Ixodes dammini Spielman、Clifford、Piesman & Corwin），达氏硬蜱被归为肩突硬蜱的次主观同物异名（依据《国际动物命名法规》第23条）。
