Intraspecific Variation and Molecular Phylogeny of Oligonychus Species (Acari: Tetranychidae) on Maize and Sorghum

Abstract

Intraspecific variation among Oligonychus populations infesting maize (Zea mays L.) and sorghum (Sorghum bicolor L.) was assessed to clarify species boundaries and phylogenetic relationships within Tetranychidae using integrated morphological and molecular approaches. Field-collected mite populations were examined for diagnostic morphological traits under light microscopy, followed by DNA barcoding using mitochondrial cytochrome c oxidase subunit I (COI) and ribosomal ITS2 regions. Sequence divergence analyses revealed notable genetic differentiation among populations associated with both host crops, indicating host-associated lineages within nominal species. Phylogenetic reconstruction using maximum likelihood methods clustered isolates into distinct clades corresponding to host plant association rather than geographic origin, suggesting potential cryptic speciation events. Morphometric variability in empodial claw structure, dorsal setae length, and aedeagus shape supported molecular clustering patterns. High intraspecific divergence values exceeded conventional thresholds for Tetranychidae species delimitation, highlighting hidden diversity within Oligonychus complexes. The integration of morphological and molecular datasets improved resolution of taxonomic ambiguity and provided evidence for host-driven diversification. These findings emphasize the importance of combining DNA-based identification tools with classical taxonomy for accurate pest diagnostics in cereal agroecosystems. Improved understanding of Oligonychus phylogeny will aid in developing targeted integrated pest management strategies for maize and sorghum production systems, particularly in regions experiencing recurring spider mite outbreaks.