| The Cydia pomonella and Grapholita molesta (Busck)(Lepidoptera, Tortricidae) are the important pests for fruit trees. They are the economically most destructive pest species of stone and pome fruits worldwide. The distribution, an extensive host and environmen between them have the complex interactions that they have an important influence on population genetic structure, which makes it difficult to control these pests. It is of great urgency to find out the population genetic structure of the Cydia pomonella and Grapholita molesta in China, analyze their phylogeography and predict their diffusion approach.This study is the first time to deal with the phylogenetic relationships among10Cydia pomonella and16Grapholita molesta populations in China, respectively. The mitochondrial DNA and the lineage biogeography were used to infer the demographic history and differentiation mechanism of the Cydia pomonella and Grapholita molesta. The principle achievements of this study concluded and listed as below:1. The4mtDNA genes of the194individuals from10Cydia pomonella and the186individuals from16Grapholita molesta populations were amplified, respectively. We obtained and submitted to GenBank33different haplotypes, including16halotypes of the CO I genes and17haplotypes of the CO II genes.2. The data of the mtDNA show that the Grapholita molesta has obvious genetic differentiation and the Cydia pomonella has low and frequent gene flow between populations. The Grapholita molesta’s genetic varitation more higher than the Cydia pomonella. The Grapholita molesta’s nucleotide diversity is0.01%and0.04%, and the variable sites is21.7%and52.3%, respectively. The variable sites6.2%and7.6%is to Cydia pomonella, respectively.3. Combined with the MP tree and the statistical parsimony networks from the mtDNA4genes, the conclusion were gained that there are low genetic differenation between the populations of the Cydia pomonella, and the Grapholita molesta propably has diverse and geographically localized clades in China, namely, the northwest, the northeast and north China, which are isolated by mountains and rivers.4. Neutrality tests show that the Cydia pomonella’s Tajima’ s D is significant negative and not significant, which is following the neutral model in evolution. Fu’ F statistic was negative or even positive for various subgroups of samples. Among Grapholita molesta populations, Fu’ F was positive and was negative or even positive, which showed the strong population subdivision was evident. All Tajima’ s D demonstrated that the Cydia pomonella and Grapholita molesta have the population expansion, and the population is expand its distribution year by year.5. Correlations between genetic diversity and latitude and between gene flow level and the geographic distance among populations show that the related coefficient between the genetic distance and geographic distance of the Cydia pomonella is low and not significant, there are significant negative between the haplotype diversitys and the longitude. The Cydia pomonella have a clear trend of spreading across its range from west to east China. There positive significant between genetic diversity and latitude (r=0.5350, P=0.3274) and the significant negative between genetic distance and geographic (r=0.052, P=0.021) of the Grapholita molesta. The expand process of the Grapholita molesta from east to west, and from west to north, namely, Heilongjiang-Xinjiang-Shandong, and Xinjiang-Hebei-Inner Mongolia or Heilongjiang-Anhui-Shandong. The high shared haplotype indirected there existed frequent gene flow through the results of the habitat and geographic distance interaction.These findings that the Cydia pomonella and the Grapholita molesta have small long-term effective population sizes, limited genetic flow between adjacent populations, and strong isolation-by-distances relationships, support the idea that populations of the two species are at or very close to genetic equilibrium, and the observed differentiation of the Grapholita molesta among these regions is likely the result of migration-drift equilibrium.6. Based on2.3%/a million years (Myr), the coalescenc time (equated with the onset of demographic or range expansion) for Cydia pomonella about12000years and the Grapholita molesta approximately170000, respectively. This implies that the differentiation of the Grapholita molesta is probably due to a climate and geographic distance interaction. The Cydia pomonella has genetic differenation only between Heilongjiang province and Xinjiang province, which may be the results of the natural selection to adapt the cold climate in the northeast China. |
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