What is the status of Ixodes inopinatus (Ixodidae)?

Abstract

The original description of Ixodes inopinatus is predominantly based on morphological and ecological characteristics. It was postulated that I. inopinatus is a cryptic species of the Ixodes ricinus complex, mainly found in the Mediterranean region of Spain, Portugal, Morocco, Algeria, and Tunisia. Although definitive proof is lacking, genetic insights support that I. inopinatus is a distinct species, but that the morphological characteristics, particularly from the adult stages, as well as molecular features, might not be distinctive enough for identification. In this study, we re-examined and expanded recently published results on the molecular relationships between I. ricinus and I. inopinatus, using the complete mitogenomes of 44 specimens of I. ricinus, 3 of Ixodes persulcatus, 3 of either Ixodes pomerantzevi, Ixodes scapularis, or Ixodes pacificus, and 6 of I. inopinatus from Northern Africa; the latter were identified as I. ricinus (in part) in previous reports. We managed to demonstrate that I. inopinatus has unique mitochondrial genomic features that allow the complete separation from I. ricinus collected in Europe. All specimens of I ricinus in Europe belong to four mitogenome clades that lack clear geographical structuring. Specimens found in Northern Africa belong to a fifth population. Although specimens of I. inopinatus have been reported in Central Europe, their link with such a fifth mitogenome has not yet been documented. To confirm the link between genetics and morphology, we recommend additional studies, ideally based on nymphs of I. ricinus and I. inopinatus, since they allow adequate morphological separation. Efforts should be directed to manage laboratory colonies to check for reproductive isolation, hybridization, and performance under different conditions of temperature and humidity.