What is the status of Ixodes inopinatus (Ixodidae)?

The original description of <i>Ixodes inopinatus</i> is predominantly based on morphological and ecological characteristics. It was postulated that <i>I. inopinatus</i> is a cryptic species of the <i>Ixodes ricinus</i> complex, mainly found in the Mediterranean region of Spain, Portugal, Morocco, Algeria, and Tunisia. Although definitive proof is lacking, genetic insights support that <i>I. inopinatus</i> 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>I. ricinus</i> and <i>I. inopinatus</i>, using the complete mitogenomes of 44 specimens of <i>I. ricinus</i>, 3 of <i>Ixodes persulcatus</i>, 3 of either <i>Ixodes pomerantzevi</i>, <i>Ixodes scapularis</i>, or <i>Ixodes pacificus</i>, and 6 of <i>I. inopinatus</i> from Northern Africa; the latter were identified as <i>I. ricinus</i> (in part) in previous reports. We managed to demonstrate that <i>I. inopinatus</i> has unique mitochondrial genomic features that allow the complete separation from <i>I. ricinus</i> collected in Europe. All specimens of <i>I ricinus</i> 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>I. inopinatus</i> 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>I. ricinus</i> and <i>I. inopinatus</i>, 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.