Data from: DNA barcoding fishes from the Congo and the Lower Guinean provinces: assembling a reference library for poorly inventoried fauna

The Congolese and Lower Guinean ichthyological provinces are understudied
hotspots of the global fish diversity. Here, we barcoded 741 specimens
from the Lower and Middle Congo River and from three major drainage basins
of the Lower Guinean ichthyological province, Kouilou-Niari, Nyanga and
Ogowe. We identified 195 morphospecies belonging to 82 genera and 25
families. Most morphospecies (92.8%) corresponded to distinct clusters of
DNA barcodes. Of the four morphospecies present in both neighbouring
ichthyological provinces, only one showed DNA barcode divergence
<2.5%. A small fraction of the fishes barcoded here (12.9% of the
morphospecies and 16.1% of the barcode clusters representing putative
species) were also barcoded in a previous large-scale DNA analysis of
freshwater fishes of the Lower Congo published in 2011 (191 specimens, 102
morphospecies). We compared species assignments before and after taxonomic
updates and across studies performed by independent research teams and
observed that most cases of inconsistent species assignments were due to
unknown diversity (undescribed species and unknown intraspecific
variation). Our results report more than 17 putative new species and show
that DNA barcode data provide a measure of genetic variability that
facilitates the inventory of underexplored ichthyofaunae. However,
taxonomic scrutiny, associated with revisions and new species
descriptions, is indispensable to delimit species and build a coherent
reference library.