Molecular-Based Taxonomic Inferences of Some Spider Mite Species of the Genus Oligonychus Berlese (Acari, Prostigmata, Tetranychidae)

Simple Summary Spider mites belonging to the genus Oligonychus Berlese are serious pests of various fruits, ornamentals, agronomic crops, and trees. To effectively manage these pests, their accurate identification is crucial. Morphological-based identification of Oligonychus species is very challenging. The present study used molecular data to identify/confirm the species identity of some Oligonychus species, including various samples lacking male specimens. Moreover, phylogenetic analyses validated the morphological-based subdivision of the genus Oligonychus. The integrative taxonomic approaches are vital for accurately identifying closely related Oligonychus species. DNA barcoding technology using short DNA sequences has emerged as an efficient and reliable tool for identifying, confirming, and resolving closely related taxa. This study used ITS2-rDNA and mtCOI DNA sequences to confirm the identity of eight Oligonychus species, representing 68 spider mite samples, collected mainly from Saudi Arabia (SA) and some from Mexico, Pakistan, USA, and Yemen. The intraspecific nucleotide divergences of the studied Oligonychus species ranged from 0% to 1.2% for ITS2 and 0% to 2.9% for COI. However, the interspecific nucleotide divergences were distinctly higher than the intraspecific ones and ranged from 3.7% to 51.1% for ITS2 and 3.2% to 18.1% for COI. Furthermore, molecular data correctly confirmed the species identity of 42 Oligonychus samples lacking males, including a previously claimed sample of O. pratensis from SA. High genetic variations were detected in two Oligonychus species: O. afrasiaticus (McGregor) (nine ITS2 and three COI haplotypes) and O. tylus Baker and Pritchard (four ITS2 and two COI haplotypes). In addition, ITS2- and COI-based phylogenetic trees confirmed the subdivision of the genus Oligonychus. In conclusion, integrative taxonomic approaches are vital to resolve the closely related Oligonychus species, identify the samples lacking male specimens, and assess phylogenetic relationships within and among species.