Structure and molecular evolution of the barcode fragment of cytochrome oxidase I (COI) in Macrocheles (Acari: Mesostigmata: Macrochelidae)

Consisting of approximately 320 species, Macrocheles is the most widely distributed genus in the family Macrochelidae. Though some studies have focused on the description of Macrochelidae using molecular techniques (e.g., RAPD) and sequencing of some genes, the interspecies relationships within Macrocheles still remain uncertain. As such, in the present study, we examine all publicly available data in GenBank to explore the evolutionary relationships, divergence times, and amino acid variations within Macrocheles. Exploring the patterns of variation in the secondary protein structure shows high levels of conservation in the second and last helices, emphasizing their involvement in the energy metabolism function of the cytochrome oxidase subunit I enzyme. According to our phylogenetic analysis, all available Macrocheles species are clustered in a monophyletic group. However, in the reconstructed trees, we subdivided M. merdarius and M. willowae into two well‐supported intraspecific clades that are driven by geographic separation and host specificity. We also estimate the divergence time of selected species using calibration evidence from available fossils and previous studies. Thus, we estimate that the age of the Parasitiformes is 320.4 (273.3–384.3) Mya (Permian), and the Mesostigmata is 285.1 (270.8–286.4) Mya (Carboniferous), both with likely origins in the Paleozoic era. We also estimate that Macrocheles diverged from other Mesostigmata mites during the Mesozoic, approximately 222.9 Mya. In the present study, we used all available data to explore the evolutionary relationships, divergence time, and amino acid variation of COI barcode fragment of Macrocheles. Our results revealed the less conserved structure of COI in Macrocheles species compared with arthropods. Exploring the variation pattern based on the secondary and three‐dimensional structures of proteins indicates the high level of conservation in the second and last helices emphasizing their involvement in the energy metabolism function of the COI enzyme. According to our phylogenetic analysis, all available Macrocheles species have been clustered in a phylogenetic group. However, due to poor sampling and lack of enough data, our phylogenetic study cannot reflect the true evolutionary relationships between Macrocheles species. In the reconstructed trees, M. merdarius and M. willowae were subdivided into two well‐supported intraspecific clades, which are driven by geographic separation and host s