关键词: 齿小蠹属, DNA条形码, 线粒体COⅠ基因, 遗传距离, 系统发育树

Abstract: Species of the genus Ips (Coleoptera: Scolytidae) are often intercepted and captured in quarantine at port. To explore the feasibility of identifying Ips species rapidly and accurately by DNA barcode of special sequence in mitochondrial cytochrome c coxidase subunit Ⅰ (CO Ⅰ), the 462 bp sequence of mitochondrial CO Ⅰ gene in Ips spp. was measured and analyzed. The sequence analysis results revealed that there are 259 mutation sites, 203 conserved sites, 181 parsimony-informative sites and 78 singletons in this gene. Among all sites, the average proportion of base A, G, C and T are 35.8%, 17.2%, 16.5% and 30.5%, respectively. A+T base pair accounts for 66.3% of the mitochondrial CO Ⅰ gene, which is significantly higher than that of G+C base pair and shows an obvious preference to A+T in the sequence. The numbers of A and T are equal, conforming to the basic feature of base composition in insect mitochondria. The result of transition and transversion showed that the sequence did not reach saturation and an evolution analysis can be achieved accurately. Model Kimura 2-parameter was used to analyze the genetic distance, and the results showed that the genetic distance among the same species varied from 0.002 to 0.007, while that among different species ranged from 0.056 to 0.431 with the average value of 0.199, confirming that the genetic distance can be used to discriminate different species. Neighbor-joining phylogenetic tree was built based on the CO Ⅰ gene sequences, and the result indicated that the same species was gathered in the same branch, with the bootstrap value of 100% and the related species could also gather in the same branch, with a high confidence (≥97%). The results suggest that DNA barcoding based on mitochondrial CO Ⅰ gene sequences is applicable in the classification and identification of Ips species.

Key words: Ips, DNA barcoding, mtDNA COⅠ gene, genetic distance, phylogenetic tree