| Grapholita molesta(Busck)(Lepidoptera: Tortricidae) is a worldwide pest insect causing serious damages to the global economy of fruit industry. The species is believed to originate in Northwest China, and widely distribute in East Asia. G. molesta becames one of the important quarantine pest worldwide for the invasion into Europe and America via fruit importation. G. molesta now widely distributes in the main fruit producing areas of China, north to Heilongjiang and South to Guangdong, with 3-7 generations per year. The main factors that affect the distribution is temperature, therefore, the rapidly adaption to the alien environment results in widely distribution all over the world. Under global warming, insects are shown more susceptible under heat stress. As a native species of China with long term adapt to local environment, the study on impact of temperature acclimation effects, especially high temperature tolerance, can provide opportunities to understand the reason why G. molesta distributed widely in such a short term.In this thesis, we use microsatellite to study genetic structures of G. molesta populations and explore if different structure existence along with significant heat tolerance phenotypes under chronic and acute heat shock respectively. We then examine the heat shock protein expression pattern to explain potential genetic bases of heat phenotypes among populations. The thesis aims to reveal the impacts under long-term selection from evolutionary adaptation aspect in G. molesta. In addition, we also study the temporal microevolution within a population. Tangshan population from Hebei Province was chosen to rear in the laboratory for one and two years under constent conditions. By comparing the differences between laboratory population and wild population of life traits, heat resistance and genetic structures, we reveal the rapid phenotypic plasticity within five generations. Conclusions are drawn as follows:1. Five populations(Shengyang, Tangshan, Dangshan, Wuhan, Guangzhou) of G. molesta in China exist significant differentiation of genetic basis. Microsatellite results show that genetic diversity among populations were higher(D>0.65), with the characteristic of a native species. Howvere, the heterozygote excess is one of the significant characteristics in each population(Ho>0.80), suggesting the weak flight ability of G. molesta. G. molesta of Anhui population showed closer relationship with other northern populations. Gene flow Fst revealed significant differences among populations, also conform to IBD rules.2. There are significantly phenotypic variations among populations, such as the longest life cycle in Guangzhou population, largest pupal weight in Shenyang population. For G. molesta developmental duration, Guangzhou and Shenyang populations are longer than Wuhan and Tangshan populations, while Anhui populatoin is the shortest. The heat tolerance of Guangzhou population significantly shows the rapidest thermal tolerance than any other populations, while the northern Shenyang population tolerance is the worst both in acute and chronic heat stress. G. molesta from Guangzhou and Wuhan have no difference in heat tolerance as southern populations. Heat shock protein expressions also reflect the same trend.There was a positive correlation between Hsp expression and heat tolerance.3. Population from Tangshan Hebei were reared for one and two years in laboratery. To compare with the wild populations on thermal tolerance and life history phenotypes, we find that the lab strains with the faster growth rate, lighter pupal weight, and mean heat tolerance. On contrast, wild population shows great variability, weak chronic heat tolerance, but with the better rapid reactive capability. Heat shock protein expressions also reflect the same trend, suggesting the fast adjustment ability of wild population than lab populations. These results show the possible microevolution of fast adaptability in G. molesta. |
PDF Full Text Request