Molecular System Geography Of The Locusts Of Rhizoctonia Solani Based On The Mitochondrial Gene Sequence

The bamboo locust, Rammeacris kiangsu (Tsai), is one of the most important pests of bamboos in China. The nymphs and adults of this species mainly feed in large groups on the leaves of bamboo plants, often causing new culms to die and production of new shoots to decrease. Great efforts have been made in the study of this species in order to find effective strategies and methods for its control. Though the bamboo locust is the significant pests of bamboos and the biological and physiological characteristics of the species have been already understood, there is little research about its population genetic structure and population migration. This phenomenon is not very helpful to the control of bamboo locust.In order to evaluate the genetic variation and genetic strueture of the isolated reed parrotbill populations three fragments of mitochondrial DNA (mtDNA) sequences (COâ… , COâ…¡and ND2) were used to examine the population genetic and phylogeographical structure and population demography of Rammeacris kiangsu among its distribution range. There were none (ND2 data) or significant (COâ…¡data) population genetic structure values for the R. kiangsu by AMOVA method. The phylogenetic analyses exhibited some very shallow genealogy, all the analysis did not divide the bamboo locust haplotypes into independent groups, but some haplotypes of two sample sites of Yunnan, Changning of Sichuan and Jinyun Mountain of Chongqing and Guangning of Guangdong were clustered to one lineage respectively. The phylogenetic analyze results were corresponded to networks of haplotypes for R. kiangsu.The results, including low nucleotide diversity and haplotype diversity from moderate to relative high, the wide geographic distribution of common and not strait geographic distribution of rare haplotypes and the absences of phylogeographical structure for three different molecular markers, suggestted that high gene flow is the most important factor infecting the population genetic structure of R. kiangsu. The Wuyi Mountain and Nanling Mountain coupled with some other mountains in southern China were not effective barriers limiting gene exchange between neighbouring populations on the both sides of these mountain ranges. A recent and sudden population expansion of this locust were also supported by the median-joining networks. The approximate expansion time based on COI data was 0.188 million years ago, which was the next to the last inter glaciation period of the Quaternary glaciation. This estimated time before the last glacial maximum (about 18000 million years ago). Populations of this species most likely originated in AH, GN and ML populations, due to these areas harbour greater genetic diversity and higher number of haplotypes. The shallow phylogeny trees are evidences of high movement rate between neighbouring habitats, colonization processes and long-distance migration. This finding is important to the perspective of control measures of this locust, because it suggestted that control measure might be effective only if it can be implemented simultaneously for the whole distribution range.Fluctuations in climatic and ecological or environmental conditions during the Quaternary glaciations play a important role in the genetic diversity and population demography.