Cywinska A, Hannan M A, Kevan P G, Roughley R E, Iranpour M, Hunter F F
Department of Biological Sciences, Brock University, St Catharines, Ontario, Canada.
Med Vet Entomol. 2010 Dec;24(4):382-410. doi: 10.1111/j.1365-2915.2010.00896.x.
This paper reports the first tests of the suitability of the standardized mitochondrial cytochrome c oxidase subunit I (COI) barcoding system for the identification of Canadian deerflies and horseflies. Two additional mitochondrial molecular markers were used to determine whether unambiguous species recognition in tabanids can be achieved. Our 332 Canadian tabanid samples yielded 650 sequences from five genera and 42 species. Standard COI barcodes demonstrated a strong A + T bias (mean 68.1%), especially at third codon positions (mean 93.0%). Our preliminary test of this system showed that the standard COI barcode worked well for Canadian Tabanidae: the target DNA can be easily recovered from small amounts of insect tissue and aligned for all tabanid taxa. Each tabanid species possessed distinctive sets of COI haplotypes which discriminated well among species. Average conspecific Kimura two-parameter (K2P) divergence (0.49%) was 12 times lower than the average divergence within species. Both the neighbour-joining and the Bayesian methods produced trees with identical monophyletic species groups. Two species, Chrysops dawsoni Philip and Chrysops montanus Osten Sacken (Diptera: Tabanidae), showed relatively deep intraspecific sequence divergences (∼ 10 times the average) for all three mitochondrial gene regions analysed. We suggest provisional differentiation of Ch. montanus into two haplotypes, namely, Ch. montanus haplomorph 1 and Ch. montanus haplomorph 2, both defined by their molecular sequences and by newly discovered differences in structural features near their ocelli.
本文报道了标准化线粒体细胞色素c氧化酶亚基I（COI）条形码系统用于鉴定加拿大虻和厩螫蝇适用性的首次测试。另外使用了两个线粒体分子标记来确定是否能在虻类中实现明确的物种识别。我们的332个加拿大虻类样本产生了来自5个属和42个物种的650个序列。标准COI条形码显示出强烈的A+T偏向性（平均68.1%），尤其是在第三密码子位置（平均93.0%）。我们对该系统的初步测试表明，标准COI条形码对加拿大虻科昆虫效果良好：目标DNA可以很容易地从小量昆虫组织中回收，并对所有虻类分类单元进行比对。每个虻类物种都拥有独特的COI单倍型组，能很好地区分不同物种。同种的平均Kimura双参数（K2P）差异（0.49%）比种内平均差异低12倍。邻接法和贝叶斯法产生的树都具有相同的单系物种组。两种虻，道氏斑虻Chrysops dawsoni Philip和山地斑虻Chrysops montanus Osten Sacken（双翅目：虻科），在所分析的所有三个线粒体基因区域中都显示出相对较深的种内序列差异（约为平均值的10倍）。我们建议将山地斑虻暂时分为两个单倍型，即山地斑虻单倍型1和山地斑虻单倍型2，两者都由其分子序列以及在单眼附近新发现的结构特征差异来定义。
