DNA barcoding of non-biting midges (Diptera: Chironomidae)

Non-biting midges have a great potential as biological indicators in assessments of freshwater ecosystems, but are rarely taken full advantage of. The main reasons for this is the limited knowledge of larval taxonomy, the restricted access to taxonomic expertise, and the need for time and resource demanding procedures for the required species level identification. Consequently, a system for species identification and life stage association by comparisons of short gene sequences (i.e. DNA barcoding) could be a useful tool to profit from Chironomidae in ecological studies of freshwaters to a greater extent. To explore the possibility of identifying chironomids with partial COI gene sequences, we conducted a study on 97 specimens of 47 species in the tribe Tanytarsini. Our results show that COI from 98% of the specimens could be amplified from different life stages using the standard barcode primers (LCO1490 & HCO2198) and that interspecific genetic distances exceeded intraspecific distances for all species. All con-specific individuals grouped with 91-100% bootstrap support in parsimony analyses. This indicates that DNA barcodes are practicable tools to identify species that are already in a COI sequence library. However, the results from the neighbour joining and parsimony analyses did not otherwise reflect trustworthy phylogenetic relationships between the species examined. Thus, although DNA barcodes might be effective in associating life stages and delineating species, they are unreliable for approximate identification when sequences of the unknown taxon are absent from the COI sequence library. Nevertheless, as gene amplification and sequencing is becoming more affordable and regular practice, it would be relatively quick and inexpensive to create a COI sequence library of the most common chironomid species. Once established, a library of DNA barcodes will not only assist in rapid and accurate identification of chironomid larvae, but also in identifying taxonomic entities that deserve more thorough morphological, ecological and genetic analyses.