Abstract:

In order to understand effects of host plant, geographical distance and pesticide stress on the genetic structure of the spruce spider mite (Oligonychus ununguis), different populations of the mite were used for analyzing the sequence variation of the mitochondrial cytochrome oxidase I gene (COI) segment. Genetic differentiation was very small in the mites collected from different species of Castanea mollissima, Quercus acutissima, Q. variabilis, Q. dentate, which distributed in a narrow range(3-500 m), and in the mites from the same species of host plants that distributed in a larger area(25 km). These populations were clustered in the same branch of the NJ phylogenetic tree and the genetic distance between them was 0-0.001. There was significant genetic differentiation of the mites collected on Q. variabilis from two different districts, Taian district of Shandong Province and Jiaozuo district of Henan Province. The mites from these two provinces were distributed in two different branches of the NJ phylogenetic tree. The population suffered long period pesticide stress had significant genetic differentiation from the population that had not experienced the pesticide stress, although they were collected from the same host species of Q. acutissima away from about 500 m. Genetic distance between the two populations was 0.015, and they were clustered in the different branch. of the NJ phylogenetic tree. Results showed that geographical isolation and pesticide stress were possibly the important factors affecting population differentiation of O. ununguis.

Key words: Oligonychus ununguis, COI, host plant, geographical isolation, pesticide stress, population differentiation