The DNA barcoding project on German Diptera: An appreciative and critical analysis with four suggestions for improving the development and reliability of DNA-based identifi cation

Abstract

The progress in constructing a DNA barcode library for German Diptera as published by Moriniere et al. (2019, Mol. Ecol. Resour. 19: 900-928) is appraised from a dipterists' perspective. The coverage of the diversity of German Diptera in terms of barcode index numbers (BINs) and identifi ed barcodes is analysed and visualized in simple diagrams. The infl uence of the project setup, methodology and/or systematic effects on the emerging numbers and trends is elucidated and extensively discussed. In addition, the documentation on the species identifi cation methods in the database is assessed. Based on this evaluation, four ways for improving the future development, utility and reliability of this DNA database and similar projects in general are identifi ed: (1) Sample the collections of experts. This results in a greater and more reliable coverage within a limited time frame, as opposed to random collecting and relying on a posteriori identifi cation. (2) Give priority to medically, agriculturally or ecologically important families. Addressing these gaps will meet the most pressing needs of the community and serve as a good advertisement for the usefulness and wide applicability of the DNA barcode library. (3) Allocate resources to recruiting established experts as opposed to trainees. The fact that half of the recovered BINs remained unidentifi ed mostly results from the insufficient involvement of experts (and expert time). (4) Appropriately document the morphological identifi cations by experts in the database. This will allow to assess the reliability of DNA-based identifi cations and to prioritize confl icting identifi cations within a BIN accordingly.