Studies On Phylogenetic Relationships Among Some Important Groups Of Acaroid Mites Based On Morphological Characters And COI Gene (Acari: Acaridida)

This dissertation deals with the phylogenetic relationships among some import-ant groups of acaroid mites based on morphological characters and mitochondrialcytochrome oxidaseâ… (COI) partial sequences. The major achievements of this paperare as follows:1. The cladistic analysis of 15 species in Acaridida was performed based on 55morphological characters. Four families of Acaridida could be divided into two clades,one consisting of Chortoglyphidae+Glycyphagidae+Acaridae, the other of Pyroglyph-idae, which formed a monophyletic group and was relatively far to other families.The relationships between 5 genera of Acaridae were [(Aleuroglyphus+Tyrophagus)+Acarus]+(Caloglyphus+Suidasia). The placement of 4 species of Acarus waslargely uncertain, which can be further divided into two groups, one consisting ofA.siro+A.farris, the other of A.mmobilis+A.gracilis.2. The classical method of phenol-chloroform treatments for extracting DNAof acaroid mites was complex. An easy rapid method for preparing DNA from 20samples was recommended. The improved method was easier and more economicalthan traditional phenol-chloroform protocol.3. There was no difference in the COI gene partial sequences of Aleuroglyphusovatus among three different geographic populations, and the same result wasobtained for Tyrophagus putrescentiae.4. Molecular phylogenetic trees of 12 species in Acaridida were constructed bymaximum parsimony (MP) and neighbor joining (NJ) methods based on COI genepartial sequences (about 367bp), using Ixodes granulates and Ixodes ovatus asoutgroups. The relationships between 4 families in Acaridida were uncertain. Wefound their phylogentic relationship as (Glycyphagidae+Acaridae)+(Chortoglyphidae+Pyroglyphidae) (NJ tree) or (Acaridae+Pyroglyphidae)+(Chortoglyphidae+Glycyp-hagidae) (MP tree). The molecular phylogenetic trees showed that Acaridae wasdivided into two clades, one consisting of Aleuroglyphus+Tyrophagus+Acarus+Calo-glyphus, the other of monophyly Suidasia. The trees generated from molecular datasuggested the relationship within the genus Acarus was [(A.farris+A.mmobilis) +A.gracilis]+ A.siro.5. The phylogenetic relationships among these species within Acaridida wereexamined by combining the data of morphological characters and COI gene partialsequences. Some important relationships were suggested. (1) The relationshipsbetween 4 families of Acaridida were not well resolved in our analysis. We wouldsuggest caution in using the COI gene for mite phylogenetic studies among differentfamilies in Acaridida. (2) Among the genera of Acaridae, our results showed strongsupport for the paraphyly of this group. Aleuroglyphus and Tyrophagus were locatedin a sister group and had a close relationship. Suidasia was a monophyly, whichsupported the view of splitting the Suidasiidae from the Acafidae by OConnor'ssystem (1982). (3) The phylogenetic relationships of 4 species within the genusAcarus were well resolved based on COI gene in our analysis. A.farris andA.mmobilis were located in a sister group and had a close relationship. The resultsprove that COI gene is a useful marker to infer phylogenetic relationships amonggenera and species in the family Acaridae.