Subject areas of DNA barcoding studies of the Crustacea. Number of articles with “barcod*” and “crusta*” as keywords in their topic as retrieved from the Web of Science (period covered: 2003–2014; n = 164) and divided into six subject areas (from bottom to top): identification and barcode library (red), genetic variability (orange), species description (green), phylogenetics (violet), methods (blue), and numts (grey).