Molecular Phylogeography Of Ailanthus Altissima In Source Area And The Provenances Of Populations In Invasive Area

Ailanthus altissima (Simaroubaceae) is a woody plant originated in China. The distribution range of A. altissima China is very wide, south to Guandong、Guangxi、 Yunnan, north to Liaoning, in addition the Yangtze River and the Yellow River are the distribution center. A. altissima grow fast which can reach15meters during25years, and it has a short life. A. altissima which is a deep-rooted plant has well-developed root system, and easily to propagate. A. altissima can produce abundant fallen leaves, which could improve soil conditions. A. altissima has very strong endurance and resilience to the living environment. A. altissima can endure cold, drought, shade and so on, more over it can survival in slightly acidic and calcareous soils. A. altissima which is an important tree in urban industrial areas can resistance to dust and SO2. Since in the18th century A. altissima was brought into Europe and North Amercia, it spread quickly in these continents, further more it threated local ecological environment, and become invasive species.Based on cpDNA sequences(psbA-trnH、trnL-trnF、trnD-trnT), we studied the phylogeography of A. altissima in China and the provenances of populations from the United States. Afterwards we detailedly explore the provenance of the population of A. altissima distributed in the United States using SSR analysis. The aims of this study are:(1) to examine the genetic diversity of A, altissima in China; to discuss the species evolution history and the inter-species differentiation; to analyze the distribution of chloroplast haplotypes.(2) to examine the genetic diversity and genetic structure of A. altissima in the United States; to analyze the differentiation between populations; to presume whether the populations in invasion area experienced bottleneck and the reason led to the low genetic variation.(3) to speculate provenances of A. altissima distributed in the United States, to estimate the relationship between the populations from the invasion and the origin areas, to analyze the adaptive evolution accompanied by invade course.The main results of study on A. altissima in China are as follows:1. The genetic diversity analysis found that A. altissima had a high level of genetic diversity (π=0.0331±0.0162,H=0.8457±0.0391).2. The genetic structure showed that the differentiation between the populations in the same area is smaller than that in different area, yet there is no significant correlation between the genetic distance and the geographic distance of populations.3. The species history dynamic analysis (mismatch analysis curve had more than one peak; Tajima’s D-0.34456(P>0.10); Fu and Li’s D*test statistic:-0.32484(P>0.10); Fu and Li’s F*test statistic:-0.37459(P>0.10)) showed that A. altissima might not have sudden demographic expansion during it’s evolutionary history.4. The chloroplast haplotypes analysis found12haplotypes divided into3clades, speculated that the contiguous range expansion and the allopatric fragmentation are main reasons which led to form the current geographic pattern.5. From the result we speculated that the east China and the central China are the refuges of A.altissima during the ice period. The current distribution formed from the last glacial retreat. After glacial period A. altissima didn’t experience rapid spread, while human activities possibly led to the long-distance spread of A. altissima.The main results of study on A. altissima the United States as follows:1. The genetic diversity of A, altissima the United States is much lower than that in China, and that might be the impact of Founder effect or genetic bottleneck. The result also showed that the low genetic variation wouldn’t hinder the success of invasion. 2. The result of mismatch analysis is unimodal curve, which indicated A. altissima in Amercian has experienced a rapid population expansion. This reflects the successful invasion of A, altissima during the last300years, and it rapidly spread.3. The result of chloroplast haplotype analysis and phylogenetic tree show that the most widely spread haplotype in the United States came from China, and this haplotype has a wide range in China. There are two unique haplotypes, the occurrence of which might be related to the short life history, the ability to adapt to the environment, and producing the new genotypes with the rapid evolution during the invasion.4. From the phylogenetic relationship of the populations from the United States and China, we figured out that the most widely distributed haplotype which occupy the most of invasion area are introduced from two places, Nanjing and Anhui of China. That suggests that A. altissima in the United States were introduced by multiple invasions, and from more than one provenance.5. The genomic source analysis showed that the genome composition of populations in the United States are different from their’s source populations, and the proportion of some part of genome have grown. The result indicate that, after the successful invasion of A. altissima in the United States, they were introduced to new geographic areas and diffusion, accompanied by producing adjustments on genome to new environment conditions and the evolutionary response to habitat conditions, which were benefit to rapid evolution.