An integrative species delimitation approach uncovers eriophyoid mite <i>Diptilomiopus ligustri</i> species complex (Acariformes: Eriophyoidea)

Abstract Eriophyoid mites (Acari: Eriophyoidea) are among the smallest terrestrial arthropods possessing simplified morphological characters, which challenges the traditional morphology‐based species delimitation. The Diptilomiopus spp. exhibit further morphological degeneration (e.g., lack of genus on both legs and some opisthosoma setae). Especially, they possess high similarity in the reticulate prodorsal shield patterns, leading to cryptic species complex and hampering our understanding of species diversity. In this study, we implemented an integrated approach, including genetic distance analysis, phylogenetic analysis, population genetic structure construction, introgression test, and morphometric analysis, to delimitate the Diptilomiopus ligustri complex. We obtained 52 mitochondrial COI gene sequences and 19 whole‐genome sequences across 18 sample sites of this complex. All samples were collected from Ligustrum plants in China, which may cover their main distribution ranges. Our results demonstrate that the D. ligustri complex consists of at least four distinct species (i.e., D. ligustri , D. cf. ligustri sp1., D. cf. ligustri sp2., and D. cf. ligustri sp3.), which are genetically divergent but do not differ morphologically, assessed by principal component analysis of 27 morphological characteristics. No significant gene flow was observed among this complex. Divergence time estimates further showed that most Diptilomiopus species diverged in a short time interval at the Paleogene–Neogene boundary, indicating a rapid radiation. Our results highlight the integrated approaches in eriophyoid mite species complex delimitation.