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Data and code from: Long-branch attractions and incomplete lineage sorting explain the unstable high-level position of eriophyoid mites in the arachnid tree of life

Shao, Zi-Kai1; Hu, Yue1; Yao, Liang-Fei1; Chen, Si-Long1; Sun, Jing-Tao1; Hong, Xiao-Yue1; Xue, Xiao-Feng1

Published Jun 17, 2026 on Dryad. https://doi.org/10.5061/dryad.pg4f4qs2x

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Abstract

Eriophyoid mites (Eriophyoidea) represent a highly diverse lineage of herbivorous arthropods in the Acariformes, including over 5,000 named species that are distributed worldwide. However, their high-level phylogeny in the Arachnida is unresolved. Conflicting phylogenetic placements have been proposed for eriophyoid mites across morphological and molecular datasets, the latter usually not supporting the morphological assignment. We reconstructed the high-level phylogeny of Arachnida using genome-scale datasets and determined the countering systematic error. Our results show that the monophyly of superorder Parasitiformes and Acariformes was recovered. However, the monophyly of subclass Acari was unstable. The monophyly of all tested orders was also recovered, except for Trombidiformes, which was rendered by the monophyletic Eriophyoidea lying outside of the Trombidiformes and forming a sister group relationship to the remaining Acariformes species. The unstable position of Eriophyoidea within Acariformes may be influenced by both long-branch attractions and incomplete lineage sorting. Combined with specific morphological synapomorphies such as only two pairs of legs and fusiform body shape as well as robust molecular evidence of eriophyoid mites, we proposed that Eriophyoidea is in the basal position of Acariformes, forming a sister group to the remaining Acariformes mites. Our results resolve the high-level placement of four-legged mites and shed new lights on the arachnid tree of life.