Date Published: January 30, 2015
Publisher: Public Library of Science
Author(s): Yuichi Oba, Hitoo Ôhira, Yukio Murase, Akihiko Moriyama, Yoshinori Kumazawa, Ben J Mans.
Click beetles (Coleoptera: Elateridae) represent one of the largest groups of beetle insects. Some click beetles in larval form, known as wireworms, are destructive agricultural pests. Morphological identification of click beetles is generally difficult and requires taxonomic expertise. This study reports on the DNA barcoding of Japanese click beetles to enable their rapid and accurate identification. We collected and assembled 762 cytochrome oxidase subunit I barcode sequences from 275 species, which cover approximately 75% of the common species found on the Japanese main island, Honshu. This barcode library also contains 20 out of the 21 potential pest species recorded in Japan. Our analysis shows that most morphologically identified species form distinct phylogenetic clusters separated from each other by large molecular distances. This supports the general usefulness of the DNA barcoding approach for quick and reliable identification of Japanese elaterid species for environmental impact assessment, agricultural pest control, and biodiversity analysis. On the other hand, the taxonomic boundary in dozens of species did not agree with the boundary of barcode index numbers (a criterion for sequence-based species delimitation). These findings urge taxonomic reinvestigation of these mismatched taxa.
Insects in the family Elateridae, commonly called click beetles, is one of the most highly diversified groups of the order Coleoptera. Approximately 10,000 [1,2] or even more  elaterid species are described worldwide, although an exact number in nature is uncertain owing to the frequent discovery of new species and frequent changes in taxonomy. Since most click beetles are dull in coloration and patterning and lack peculiar characteristics in, e.g., horn or large mandible, morphological identification is generally difficult and requires taxonomic expertise. While adults are typically nectar feeders, their larvae, called wireworms, usually live in the soil or under bark. Some wireworms are serious agricultural pests on, e.g., potato, wheat, and corn, while others are active predators of other insect larvae [1,2,4]. Identifying their larvae using morphological characteristics is even more difficult. The larval period for elaterids is generally long, often 2–3 years and sometimes 10 years or longer [2,5,6]. Thus, it is not practical to identify wireworm pests collected from crop fields following their development into adults. These features call the significance of DNA barcoding of click beetles to enable their easy, rapid and accurate identification.
In this study, we assembled 762 DNA barcodes for Japanese click beetles (S1 Table), covering 74% of the common species (90% in genus) that occur on Honshu main island and 74–85% of recorded species (94–98% in genus) from several prefectures of Honshu (Table 1). Since regional Red Listing process and environmental impact assessment are usually conducted on the basis of the prefectural species lists, high coverage of barcoded species in the prefectural species list is important for practical use. All 762 individuals were carefully identified by a taxonomic expert on Elateridae (HÔ). Thus, our database satisfies the two most important factors for DNA barcode libraries, coverage and reliability .