About the Analysis of 18S rDNA Sequence Data from Trypanosomes in Barcoding and Phylogenetics: Tracing a Continuation Error Occurring in the Literature

SIMPLE SUMMARY: The variable regions (V1–V9) of the 18S rDNA are routinely used in biodiversity studies. In trypanosome research, more than 70 publications discuss the pitfalls and benefits of the V7/V8 region in trypanosome barcoding and phylogenetics. However, in light of the current 18S rDNA numbering system, V7/V8 of trypanosome research corresponds to V4 in all other organisms (including other Euglenozoa). This misunderstanding is traced back to its origin and corrected for future research. ABSTRACT: The variable regions (V1–V9) of the 18S rDNA are routinely used in barcoding and phylogenetics. In handling these data for trypanosomes, we have noticed a misunderstanding that has apparently taken a life of its own in the literature over the years. In particular, in recent years, when studying the phylogenetic relationship of trypanosomes, the use of V7/V8 was systematically established. However, considering the current numbering system for all other organisms (including other Euglenozoa), V7/V8 was never used. In Maia da Silva et al. [Parasitology 2004, 129, 549–561], V7/V8 was promoted for the first time for trypanosome phylogenetics, and since then, more than 70 publications have replicated this nomenclature and even discussed the benefits of the use of this region in comparison to V4. However, the primers used to amplify the variable region of trypanosomes have actually amplified V4 (concerning the current 18S rDNA numbering system).