DNA barcoding is a useful tool for identifying species; however, successful barcode-based identification requires a reference library of barcode sequences from accurately identified specimens. Here we present a reference library of co1 barcode sequences for the Neotropical electric knifefish order Gymnotiformes (Teleostei: Ostariophysi), a model taxon for studies of tropical diversification and biogeography, genomics, behaviour, and neurobiology. Our library contains barcodes for 167 of the ca. 270 valid species of gymnotiforms derived from geo-referenced museum voucher specimens, and includes sequences from 26 type specimens and 21 specimens from type localities, most of which we collected. To assess the state of gymnotiform barcodes in two main public barcode repositories, GenBank and BOLD, we compared the barcodes in these databases to our reference library. Our analysis shows that a considerable proportion of gymnotiform barcodes in GenBank and BOLD are mis- or unidentified. We encourage taxonomists to develop and publish barcode reference libraries composed of carefully curated barcode sequences.

We built the Gymnotiformes Barcode Reference Library using representative barcode sequences for as many described species as possible. We used specimens from the type series of each species when possible; if not, we preferentially selected specimens from (within ca. 10 km) or near (within ca. 500 km) the species type locality. We used tissues from voucher specimens deposited in museum collections. Specimens were identified using diagnostic keys and species descriptions from the primary taxonomic literature (reviewed by Ferraris Jr. et al., 2017; Fricke et al., 2022). We extracted DNA from each specimen from muscle or fin tissue, and then amplified and sequenced co1 for each specimen.