The Community Structure Of Grassland Grasshopper In Horqin Plain Hilly Meadow Steppe And Genetic Differentiation Of Oedaleus Decorus Asiaticus And O. Infernalis

I Community structureThe Horqin plain hilly meadow steppe is one of the important grassland in China. Enormous damage was caused by grasshoppers in Horqin plain hilly meadow steppe annualy. In order to suppresse the populations of the grasshoppers and to develop integrated pest management strategy for the pest, systematic studies were carry out for the study of the community structure of grasshopper including species composition, flora geographical elements, time structure, space structure and diversity as well as the relationship between grasshopper community and plant community during2011-2012. The results are as follows:1.22grasshopper species were identified which belonging to6families and17genera from the8typical plots in the grassland72.73%of the species (16species) were Oedipodidae and Arcypteridae. The palaearctic species were superior in numbers (72.73%of total number).2. The seasonal dynamic of grasshopper species and dominant species composition were affected significantly by the environment factors such as temperature and plant community. The most species which was17species identified belonging to6families and17genera was found on July20. The level of space utilize was different due to the different biological characteristics of grasshopper. Results from cluster analysis indicated that4grasshopper feeding group were present when the euclidean distance is9.5.3. Community diversity index of grasshopper was ranked successively:July>August>June>September; Community evenness index of grasshopper was ranked successively:June>August>July>September; Community richness index of grasshopper was ranked successively:July>August>September>June. The difference of parameter of grasshopper community was affected by the plant community and terrain. Community similarity index was different in different months due to the different of grasshopper community composition. The distribution of grasshopper species was affected by terrain.4. The results of grasshopper guild structure indicated that there were six guilds present in the grassland by clustering analysis, and the habitat and biocompatibility were significantly different in those six guilds which explained that diverse habitat provided a variety living space for grasshoppers. The environmental factors such as illumination and terrain with the biological characteristics of grasshopper played an important role in the distribution of grassland grasshopper. To maximize the biological fitness, the grasshopper community was divided into different resource utilization guilds. Three principal components were extracted from ecological traits. These principal components cumulated82.91%variance proportion and they represented the biological information about substrate, height up on the plant, terrain and sunlight regime. Since different species of grasshopper had different degree about utilization of environment resource that they presented diverse ecologic niche breadths and the similarity of environment requirement depended on the niche overlaps among the species.5. To understand the relationship between plant community structure, grasshopper community structure, three types of plots (Ⅰ Stipa baicalensis+Cleistogenes chinensis; Ⅱ Stipa baicalensis+C. squarrosa; Ⅲ Setaira viridis+Artemisia Pectinatal+S. baicalensis)were selected and surveyed from June to August in2012. The results indicated that the important value, height, coverage and density of plant were different significantly. The grasshoppers which own higher biomass were divided into different dominant species at different time. The species of early occurence were Bryodemella tuberculatum dilutum and Pararcyptera microptera meridionalis, the species of middle occurence were Calliptamus abbreviatus and Oedaleus decorus asiaticus, the species of late occurence was O. infernalis. Significant difference of the density and biomass among grasshopper was observed which indicated the selective adaptation to the diversity plant community for the grasshopper. The plant community diversity was negatively correlation with the grasshopper community diversity in plot Ⅰ and plot Ⅱ, and the plant community diversity was positively correlation with the grasshopper community diversity in plot Ⅲ. But the correlation above was not significant (P>0.05). The results showed that the difference of plant composition should cause the variety in the composition and dynamic for grasshoppers.II Ggenetic differentiationTwo species, O. decorus asiaticus and O. infernalis, are the dominant grasshopper species in Horqin stepp and distribute widely. Molecular marker was utilized to study the genetic structure and gene flow of geographical populations by ISSR (inter-simple sequence repeat) and mtDNA (mitochondrial DNA), the results are as follows:1.(1) Partial mtDNA CO Ⅰ and Cytb gene of O. infernalis Saussure populations were amplified and sequenced. A total of21haplotypes were defined by mtDNA CO I gene (GenBank accession: KC297197-KC297217), and genetic distance varied from0.003to0.027among these haplotypes. A total of15haplotypes were defined in mtDNA Cytb gene (GenBank accession:KC484967-KC484981), and genetic distance varied from0.002to0.007among these haplotypes. The Neighbor-Joining phylogenetic tree and haplotype network which based on the mtDNA CO I and Cytb gene showed that haplotypes were distributed in different clades and no significant geographical structure formed.(2) The total Nei’s gene diversity was0.2628, varied from0.2171to0.2563within populations. The total shannon information index was0.4129, varied from0.3257to0.3805within populations by ISSR. The total haplotype diversity was0.653, varied from0.423to0.790within populations based on mtDNA CO I gene. The total haplotype diversity was0.462, varied from0.125to0.625based on mtDNA Cytb gene. A high degree of genetic diversity displayed by O. infernalis was discoveried.(3) The overall Fst and Gst was low, and the gene flow was greater than4based on the molecular markers of ISSR and mtDNA. Molecular variance analysis (AMOVA) demonstrated that observed genetic differences mainly occur within populations, and just a little difference among populations. The pairwise genetic distance were not correlated with the natural logarithm of geographical distance among populations. These results suggest that the gene flow among population of O. infernalis is not affected by the geographical distance, and the geographical isolation is not the major factor to cause the genetic differentiation among populations of O. infernalis.2. The total Nei’s gene diversity was0.2339, varied from0.1738to0.2445within populations. The total shannon information index was0.3753, varied from0.2569to0.3568within populations by ISSR. These results show the grasshopper possess strong adaptive capacity against the change of environment.The overall Gst was0.1155, and the gene flow was3.83. The variance proportion among populations was11.55%and the variance proportion within populations was88.45%. The genetic distance among populations was not correlated with the geographical distribution. These results reveal that the level of gene flow among different populations is high, however, the degree of genetic differentiation is low, gene low is not affected by the geographical distance.