Integrative morphometric and molecular evidence of host specialization and cryptic speciation in leaf blister mites...

Blister-forming eriophyoid mites of the genus Eriophyes are important pests of rosaceous plants and have traditionally been regarded as polyphagous species with broad host ranges. However, increasing evidence suggests that many eriophyoids represent complexes of cryptic species or host-associated lineages. In this study, we applied an integrative taxonomic approach to investigate the taxonomic status of Eriophyes populations associated with Malus domestica, Pyrus spp., and Sorbus aucuparia. We analyzed mitochondrial COI and nuclear D2 region of 28 S rDNA sequences from multiple populations, together with multivariate morphometric analyses based on 28 quantitative morphological characters. Phylogenetic reconstruction and species delimitation analyses (bPTP) revealed strong host-associated genetic structuring and identified up to seven deeply divergent evolutionary lineages. Mitochondrial COI data resolved multiple host-specific clades with high inter-lineage divergence, while the more conserved nuclear D2 marker supported major host-associated groupings but recovered fewer lineages, indicating mito-nuclear discordance consistent with recent or ongoing divergence. Morphometric analyses detected statistically significant differentiation among host-associated populations; however, extensive overlap in diagnostic characters was observed, particularly between pear- and rowan-associated mites, indicating cryptic speciation. In contrast, mites associated with apple exhibited clearer morphological differentiation consistent with molecular clustering. Our results demonstrate that leaf blister mites associated with rosaceous hosts represent a complex of distinct, host-specialized species. These findings highlight the limitations of morphology-based taxonomy in Eriophyoidea and underscore the need for integrative approaches to accurate species delimitation, with important implications for vector identification and improved pest management.