Assessment of four DNA fragments (COI, 16S rDNA, ITS2, 12S rDNA) for species identification of the Ixodida (Acari: Ixodida) - PubMed (original) (raw)

Comparative Study

doi: 10.1186/1756-3305-7-93.

Shaoqiang Wu, Yongning Zhang, Yan Chen, Chunyan Feng, Xiangfen Yuan, Guangle Jia, Junhua Deng, Caixia Wang, Qin Wang, Lin Mei, Xiangmei Lin 1

Affiliations

Comparative Study

Assessment of four DNA fragments (COI, 16S rDNA, ITS2, 12S rDNA) for species identification of the Ixodida (Acari: Ixodida)

Jizhou Lv et al. Parasit Vectors. 2014.

Abstract

Background: The 5' region of cytochrome oxidase I (COI) is the standard marker for DNA barcoding. However, COI has proved to be of limited use in identifying some species, and for some taxa, the coding sequence is not efficiently amplified by PCR. These deficiencies lead to uncertainty as to whether COI is the most suitable barcoding fragment for species identification of ticks.

Methods: In this study, we directly compared the relative effectiveness of COI, 16S ribosomal DNA (rDNA), nuclear ribosomal internal transcribed spacer 2 (ITS2) and 12S rDNA for tick species identification. A total of 307 sequences from 84 specimens representing eight tick species were acquired by PCR. Besides the 1,834 published sequences of 189 tick species from GenBank and the Barcode of Life Database, 430 unpublished sequences representing 59 tick species were also successfully screened by Bayesian analyses. Thereafter, the performance of the four DNA markers to identify tick species was evaluated by identification success rates given by these markers using nearest neighbour (NN), BLASTn, liberal tree-based or liberal tree-based (+threshold) methods.

Results: Genetic divergence analyses showed that the intra-specific divergence of each marker was much lower than the inter-specific divergence. Our results indicated that the rates of correct sequence identification for all four markers (COI, 16S rDNA, ITS2, 12S rDNA) were very high (> 96%) when using the NN methodology. We also found that COI was not significantly better than the other markers in terms of its rate of correct sequence identification. Overall, BLASTn and NN methods produced higher rates of correct species identification than that produced by the liberal tree-based methods (+threshold or otherwise).

Conclusions: As the standard DNA barcode, COI should be the first choice for tick species identification, while 16S rDNA, ITS2, and 12S rDNA could be used when COI does not produce reliable results. Besides, NN and BLASTn are efficient methods for species identification of ticks.

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Figures

Figure 1

Figure 1

Data collection and phylogenetic screening of sequences. (A) Localities where the 84 tick specimens used in this study were collected. (B) Phylogeny of ticks resulting from Bayesian analysis of COI. Numbers on branches are posterior probabilities. ○, sequence amplified from our specimens; △, previously published sequences; □, unpublished sequences included in data set; ■, misplaced unpublished sequences excluded from data set.

Figure 2

Figure 2

Frequency distributions of K2P distances of COI, 16S rDNA, ITS2 and 12S rDNA within and among tick species. Panels show the distributions of minimum inter-specific K2P distances (A, C, E, G) and of coalescent depths (B, D, F, H) for COI (A, B), 16S rDNA (c, d), ITS2 (E, F) and 12S rDNA (G, H).

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