The Study On Morphological Variation And Genetic Diversity Character Of Onthophagus Gibbulus In The Mid-Eastern Inner Mongolia

Onthophagus gibbulus belonged to Onthophagus, Scarabaeidae, Scarabaeoidea, Coleoptera. It was a coprophagous scarabs with mammal dung. In this study, its biological characters were summarized, characters of male genital and the external form of larva were described. Morphological Markers and RAPD molecular technique were applied to study the genetic diversity,and correlation between genetic and several entironment factors of O.gibbulus populations sampled from serevral typical habitats in the middle and eastern part of Inner Mongolia. Results as follow:Seven geographic O.gibbulus populations collected from the middle part of Inner Mongolia were analyzed by Random Amplification Polymorphism DNA (RAPD) molecular technique. RAPD amplification was conducted with 16 primers, Popgene software analyses indicated that 363 polymorphic loci were detected, with percentage of polymorphic loci (P) being 100%. The total Nei's gene diversity (h) was 0.280, and Shannon's information index (H) was 0.433, indicating a high level of genetic diversity of O. gibbulus; Analysis of molecular variance (AMOVA) demonstrated that the among-population component accounted for 12.57% of the total variation, while the within-populations component accounted for 87.43%, and the genetic differentiation coefficient (Gst) among the populations was 0.158; Arlequin software analysis demonstrated that the coefficient of genetic differentiation among the populations were low, between 0.050 and 0.180, and the gene flow value Nm among the populations were 2.278～9.507, which indicated a strong gene flow among the populations.Morphological data of O.gibbulus collected from eight populations in the middle and eastern part of Inner Mongolia, and 13 morphometric characters were measured from 357 adult specimens and the level of morphological similarity among sites was calculated using multivariate analysis techniques. The cluster analysis indicated that the 8 populations divided into two branches, seven populations from middle part was one branch, eastern population was another one. I.e., morphological variation level among populations of O.gibbulus from middle part was lower than that between middle and eastern populations. Mantel t-test revealed that in large geographical scale the populations'genetic variation was positively correlated with the geography distance. Discriminant analysis established the discriminant functions of these eight populations, and revealed that the percentage of discriminant were between 26.2%～81.3%, and total percentage of discriminant 44.3%. The centers of 2D-plots of discriminant functions of the middle part population were closer than that between middle and eastern populations. This result was congruent with cluster analysis.In the small geographical scale of middle part of Inner Mongolia, the cluster analysis based on RAPD dates showed the seven populations were divided into two branches. However, the cluster analysis based on morphometric dates showed the seven populations were divided into three branches. In both two analyses, Wuchuan and Chahaer populations clustered together. The Mantel-test indicated that in small geographical scale there was positive correlation between genetic variation and geography distance, but not significant. The correlation was not significant between Euclidean's distance and Nei's unbiased genetic distance of 7 different middle part populations by Mantel test. I.e., the populations'morphological differentiation has no correlation with the genetic variation.Mantel tests showed that there was significant positive correlation (P<0.01)between matrix of Euclidean's distance of O.gibbulus poulations and matrix of six environment divergences, suggesting that natural selection of environment resulted in differentiation of O.gibbulus poulations. Correlation analysis of total populations show that the genetic diversity indexes was positively correlated with altitude, but not significant (P>0.05), and was negatively correlated with annual precipitation and temperature factors(≥10℃cumulative temperature in a year, mean temperature in January and mean temperature in July) but not significant (P>0.05), and was negatively correlated with≥10℃cumulative temperature in a year significantly (P<0.05). Summarizing,≥10℃cumulative temperature in a year was the major factor causing the genetic divergence of O.gibbulus poulations.