Building the DNA barcode library of Holarctic Mycetophilidae (Diptera)

Abstract: 

The some 30 000 DNA barcoded fungus gnats (Diptera, Mycetophilidae) of the Holarctic Region, forming 1800 Barcode Index Numbers (BINs), are analysed with respect to sampling efforts, fauna composition, and species boundaries between the Nearctic (NA, largely Canada) and the Palaearctic (PA, largely Scandinavia) continents. Passive mass sampling in NA (86% of barcodes) have yielded 1210 BINs (67%), while a more targeted sampling in PA (14% of barcodes) have yielded 760 BINs (42%). Geotactic collecting methods proved more efficient (720 BINs with average of 9 sequences/BIN) than did heliotactic collecting methods (1190 BINs with average of 20 sequences/BIN). The species composition richly represents all major subfamilies and most genera on both continents, the tribe Exechiini being extraordinarily well represented with 624 (35%) of the BINs. Altogether 160 BINs (21% of PA, 13% of NA, 9% of all) are shared between the continents. Among the Scandinavian barcodes, where the taxonomic precision based on morphology is relatively high, a very good match between morphology and BINs is documented, leaving only a tiny fraction of discordant BINs and a somewhat larger proportion of potential splits yet to be analysed. The taxonomic precision of the Canadian barcodes has been greatly improved through online inspection of voucher images and ID-trees. This enabled genus placement of nearly all BINs, but lots of efforts remain to obtain species-level precision. A continuous curating and maintenance engagement is essential in order to develop and refine the DNA barcode library as a high-quality reference for nextgeneration sequencing studies.

Read the whole abstracty volume published in Genome, 2017, 60(11): 881-1019, https://doi.org/10.1139/gen-2017-0178