DNA barcoding a nightmare taxon: assessing barcode index numbers and barcode gaps for sweat bees

Area of Science:

• Entomology
• Molecular Biology
• Biodiversity Studies

Background:

• Ongoing global effort to DNA barcode over 20,000 bee species.
• Recent taxonomic revisions of Lasioglossum (Dialictus) in North America utilized integrative taxonomy.

Purpose of the Study:

• Evaluate the utility of DNA barcode data for specimen identification and discovering new taxonomic diversity within Lasioglossum (Dialictus).
• Assess the effectiveness of Barcode Index Numbers (BINs) and barcode gaps for species delimitation.

Main Methods:

• Analyzed DNA barcode data from 110 Lasioglossum (Dialictus) species.
• Estimated specimen identification success using the best close match method.
• Assessed BINs using Refined Single Linkage Analysis (RESL) and barcode gaps using Automatic Barcode Gap Discovery (ABGD).

Main Results:

• Observed a 20% error rate in specimen identification compared to current taxonomy.
• RESL showed incongruence for 44.5% of species, with 43 species in merged BINs.
• A distinct barcode gap was non-existent for the dataset; ABGD results mirrored RESL discordance.

Conclusions:

• DNA barcodes alone are misleading for species delimitation and identification in this group, particularly the viridatum species-group.
• Character-based methods may improve identification success in specific cases.
• The application of DNA barcoding for species discovery requires careful consideration, especially when a well-defined barcode gap is absent.