Rice water weevil(Lissorhoptrus oryzophilus) is an important pest of paddy rice crops in Liaoning Province that was first described as a new alien invasive species in 1992.High quality DNA was successfully isolated and RAPD was effectively used to study genetic similarity and genetic variability of this insect among 120 individuals using eight primers.The high resolution provided by random amplified polymorphic DNA(RAPDs),in combination with efficient genetic distance estimators,allowed a preliminary description of the ecology and evolution of the populations of this insect in Liaoning Province.The results are compatible with a unique event of colonization and parthenogenesis,followed by the spreading of the water weevil across the surrounding Liaoning areas.A comparison of the results obtained with different genetic distance estimators is presented that show Suizhong group(pop3) is significant difference from the others which are generally similar.It means that: 1) Populations of rice water weevil from different area have different origin;2) Its rapid spread causes mainly by east populations in Liaoning;3) Host dis-continuum limits west population spread and design host interval can control the pest extending.However,it is still thought that the spreading tracks of this insect are not defined and need to be further studied.
