Exploring the biological diversity and source species of medicinal horseflies through metabarcoding

Horseflies from the Tabanidae family play a significant role in Traditional Chinese Medicine to treat various health conditions, including coronary heart disease, stroke, headaches, liver cirrhosis, psoriasis, and hepatic carcinoma. There are 27 species of Tabaninae (Tabanidae) used as medicine and showed high morphological similarities with those for which medicinal properties have not been reported. Nonetheless, there have been reports suggesting that medicinal crude drugs sometimes contain irrelevant or false species, impacting the drug's efficacy. In this current study, we collected 14 batches, totaling 13,528 individuals, from various provinces in China. Instead of “classic” DNA barcoding strategy, we employed a high-throughput metabarcoding approach to assess the biological composition of crude drugs mixture derived from horseflies. Our analysis identified 40 Amplicon Sequence Variants (ASVs) with similarity percentages ranging from 92% to 100% with 23 previously reported species. Species delimitation methods revealed the presence of 11 Molecular Operational Taxonomic Units (MOTUs), with ten belonging to the Tabanus genus and one to Hybomitra. Tabanus sp6 displayed the highest relative abundance, and its ASVs showed close resemblance with Tabanus pleski. Our investigations revealed that the medicinal batches were biologically composed of 6 to 12 ASVs. Some batches contained ASVs that closely resembled species previously associated with false Tabanus species. In conclusion, our findings offer valuable insights into the biological composition of crude drugs derived from horseflies and have the potential to enhance the quality of these traditional medicines.