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DNA barcoding insufficiently identifies European wild bees

Noticeable declines in insect populations have become of concern. Among the system services that functioning ecosystems provide, pollination is certainly among the noteworthy. In this context, the observed declines in wild pollinators, especially wild bees, pose a threat to many natural and agricultural ecosystems.

Traditional species monitoring and specimen identification of a group as large as wild bees (20,000+ species) relies on morphological character identification, but is hindered mainly by the incomplete taxonomic and diagnostic treatment of taxa, as well as a decline in this expertise. DNA barcoding has become a standard approach for molecular identification of organisms, aiming to overcome the shortcomings of traditional biodiversity monitoring. However, its effective use in species identification depends on the completeness of DNA barcoding reference libraries. Besides containing DNA barcodes of as many species as possible, a well characterized intraspecific variability in a database greatly boosts the accuracy of DNA-based identification.

Here, we advance towards an effective molecular identification of European wild bees. We conducted a high-effort survey of wild bees at the junction of central and southern Europe, and DNA barcoded all collected morpho-species. For global analyses, we complemented our DNA barcode dataset with all relevant European species and conducted a global analyses of species delimitation, general and genus-specific barcoding gaps, and examined the error-rate in DNA data repositories. We found that i) a sixth of all specimens from Slovenia could not be reliably identified, ii) species delimitation methods show numerous systematic discrepancies, iii) there is no general barcoding gap across all bees, iv) the barcoding gap is genus-specific, but only after curating for errors in DNA data repositories.

Intense sampling and barcoding efforts in underrepresented regions and strict curation of DNA barcode repositories are needed to enhance the use of DNA barcoding for identification of wild bees.


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