Echoes of Gondwana: Antarctic mite, Maudheimia petronia (Acari: Maudheimiidae), reveals deep-time isolation and highly modified mitochondrial transfer RNAs

With an estimated 50 000–100 000 described species, mites represent the most diverse group of Chelicerata and include lineages adapted to some of the harshest environments on Earth, including those found in Antarctica. Here, we combine mitochondrial genomics, population genetics, and morphological analysis to investigate the Antarctic oribatid mite Maudheimia petronia, a putative Gondwanan relict species endemic to Victoria Land. Phylogenetic analyses based on mitochondrial protein-coding genes place Maudheimia within Brachypylina and support its affinity with Ceratozetoidea. Beyond species-level characterization, we also place our results in a broader phylogenetic context by discussing relationships within Sarcoptiformes and Oribatida to clarify higher-level evolutionary patterns. The mitochondrial genome exhibits a conserved protein-coding gene order but highly derived transfer RNAs, including extensive arm reduction, frequent mismatches, and overlapping genes. Population analysis of three isolated localities revealed geographically structured but conspecific populations, consistent with long-term persistence in Antarctic refugia. Morphological observations obtained through light and scanning electron microscopy confirmed the diagnostic characters of M. petronia and showed substantial morphological stability among populations. These results provide new insights into the evolutionary history, mitochondrial genome evolution, and historical biogeography of Antarctic oribatid mites.