Genetic Structure Of Pine Caterpillars (Dendrolimus) Populations And Its Influence Factors

In order to clarify the genetic structure of the populations of Dendrolimus, we provided the scientific basis for prevention and treatment of Dendrolimus. The Cyt b gene fragments of mitochondrial DNA of five populations of three Dendrolimus species of Pine caterpillars were amplified and sequenced, and the population examined are one population of D. punctatus punctatus Walker,one population of D. punctatus spectabilis Butler and three populations of D. punctatus tabulaeformis Tsai et Liu. The genetic polymorphism and genetic differentiation in mitochondrial DNA of the three species were analyzed with molecular biology software.(1)Thirty nine nucleotide sites showed mutation in this sequence fragment and the sequence variability was 10.1%, the measurement sequence encoding 129 amino acids, of which 11 mutations, accounting for 8.5%. Nucleotide sequences and amino acid sequences in genetic distance was 0.000-0.100 and 0. 000-0.086, indicating a low genetic variation. Average nucleotide differences of interspecies and intraspecific are 8.968 and 3.934, genetic difference mainly exist in interspecies.(2) Cyt b exhibits an A/T(73.6%) bias across all sites which was the most prominent at the third position of codon with the highest content of 86.5%. A/T bias was no significant difference among the populations. Nucleotide substitution occurred mostly at the third position. Transitions were greater than transversions, while substitutions of intraspecific populations were higher than interspecific populations.(3) Polypeptide is composed of nineteen amino acids except for glutamic acid and the most common amino acids and codons are lysine[AAA] and asparagine[AAU] and the average content of AAA,AAU is 15.00% and 10.63%respcetively. The amino acid differences have little to do among populations and within populations.(4) Defined eight different haplotypes based on the mtDNA Cyt b of Dendrolimus populations with one shared . Four haplotypes were identified in three populations of D. punctatus tabulaeformis Tsai et Liu, accounting for 50%, and with two shared. Analysis of the haplotype and its distribution based on the mtDNA Cyt b, in interspecies has more exclusive haplotypes but the exclusive haplotypes equal the shared haplotypes. Fst value and gene flow showed that genetic differentiation mostly existed in interspecies, and among the intraspecific not only the gene flow occurred, but also the genetic differences did.(5) Cluster analysis showed that the genetic distance between D. punctatus Walker and sub-species of D. punctatus tabulaeformis is relatively close, genetic differentiation exists between D. punctatus Walker and sub-species of D. punctatus spectabilis Butler and the population genetic differentiation was related to ecological environment.(6)Principle component analysis was done by DPS V7.05 software in Pine caterpillars populations of different geographical in order to show genetic diversity and the influence factors, the important factors are the altitude, average annual temperature, humidity.