DNA barcoding is of limited value for identifying adelgids (Hemiptera: Adelgidae) but supports traditional morphological taxonomy

The sequence diversity in the mitochondrial cytochrome-c oxidase I (COI) gene was evaluated as a tool for resolving differences among species of European adelgids collected from several localities across the Czech Republic. Members of 7 genera and 16 species were examined, and as outgroups, two species of Phylloxeridae were used. Sequence divergences within species were on average less than 0.15%, whereas divergences between species ranged from 0.0 to 4.12% for congeneric and to 13.24% for intergeneric comparisons. It is concluded that DNA barcoding of Adelgidae is a powerful tool for identifying genera, but at the species level it works only in those cases where there are no species complexes. Nevertheless, it can be used as a complement to traditional, morphological taxonomy.