German Ixodes inopinatus samples may not actually represent this tick species

Abstract

Ticks are important vectors of human and animal pathogens, but many questions remain unanswered regarding their taxonomy. Molecular sequencing methods have allowed research to start understanding the evolutionary history of even closely related tick species. Ixodes inopinatus is considered a sister species and highly similar to Ixodes ricinus, an important vector of many tick-borne pathogens in Europe, but identification between these species remains ambiguous with disagreement on the geographic extent of I. inopinatus. In 2018-2019, 1583 ticks were collected from breeding great tits (Parus major) in southern Germany, of which 45 were later morphologically identified as I. inopinatus. We aimed to confirm morphological identification using molecular tools. Utilizing two genetic markers (16S rRNA, TROSPA) (n=37) and whole genome sequencing of specific ticks (n=8), we were able to determine that German samples morphologically identified as I. inopinatus, genetically represent I. ricinus regardless of previous morphological identification and most likely are not I. ricinus/I. inopinatus hybrids. Further, our results showed that the entire mitochondrial genome, let alone singular mitochondrial genes (i.e., 16S), is unable to distinguish between I. ricinus and I. inopinatus. As most examples of I. inopinatus in Germany were based on morphology and mitochondrial sequences, the results of the current study brings into question whether I. inopinatus was properly identified in previous research and if this species exists in Central Europe. Our results highlight the power of utilizing genomic data in answering questions regarding tick taxonomy even when closely related species are considered. HighlightsO_LIGerman Ixodes inopinatus samples represent I. ricinus based on genomic data C_LIO_LIThe mitochondrial genome is not sufficient for delineation of I. inopinatus and I. ricinus C_LIO_LIGerman samples most likely do not represent I. ricinus/I. inopinatus hybrids C_LI