中国大陆拟果蝇(Drosophila simulans)的随机扩增多态性DNA分析

近几年发现了拟果蝇(Drosophila simulans)在中国大陆的广泛分布。用随机扩增多态性DNA(RAPD)方法研究了中国大陆38个不同地理群体的拟果蝇(D．slmulam)在DNA水平上的遗传多样性，初步讨论了拟果蝇在中国大陆的起源。以40种10bp长的寡聚核苷酸随机引物进行PCR扩增，根据遗传距离利用UPGMA法作出的相关聚类图显示：(1)38个地理群体按纬度以南京(NJ)为界明显地分为南北两大支系，北方支系以北京(BJ)为界又分为明显的两个亚支，一支为东北支系包括漠河、海拉尔、黑河、佳木斯、哈尔滨、长春、沈阳、丹东、延吉、图们等10个群体；另一支包括北京、大同、呼和浩特、银川、西宁、兰州、太原、石家庄、烟台、济南、徐州、连云港等12个群体。南方支系包括郑州、武汉、上海、南京、杭州、重庆、南昌、温州、长沙、贵阳、福州、昆明、厦门、广州、南宁、海南等16个群体。(2)各地理群体之间的遗传距离与地理分布有密切关系，基本按地理位置的相关性聚类在一起。根据了解到的事实，(1)拟果蝇在中国是一个外来种；(2)拟果蝇在中国大陆的入侵是最近30年左右的事情；(3)拟果蝇在全国的广泛分布是最近10多年的事情。所以拟果蝇各群体的聚类关系可能并不是地理分化的结果，而是由于建立各地方群体的祖先群体或个体本身具有不同的遗传组成，但是某些地理上相邻近的群体可能拥有共同的祖先群体或个体，从而造成了拟果蝇各地方群体随地理分布关系而聚类。推测有两种可能的原因会产生以上结果：一是中国大陆的拟果蝇有多个不同的来源；二是拟果蝇在扩张过程中经历了可产生奠基者效应或瓶颈效应的偶然事件。

Random Amplified Polymorphic DNA(RAPD) Analysis of Drosophila simulans in the Mainland of China

The widespread distribution of Drosophila simulans in the mainland of China was found recently.Random amplified polymorphic DNA (RAPD) was used to analyze DNA polymorphisms of 38 Drosophila simulans populations collected from the mainland of China.The origins of D.simulans in China were also discussed.Using 40 arbitrary primers (10 bp),we made PCR amplifications under the optimized reaction conditions for RAPD that had been established in our laboratory.Our molecular phylogenetic tree constructed by UPGMA method showed as follows:(1) 38 populations are apparently classified into Northern cluster and Southern cluster,where NJ(Nanjing) can be considered as the boundary according to latitude.The populations in the Northern cluster can be further grouped into two sub clusters, where BJ(Beijing) can be considered as the boundary according to latitude.The Northeast one consists of 10 populations,including Mohe(MH),Hailaer(HLR),Heihe(HH),Jiamusi(JMS),Haerbin(HRB),Changchun(CC),Shenyang(SY),Dandong(DD),Yanji(YJ),Tumen(TM);the other consists of 12 populations,including Beijing(BJ),Datong(DT),Huhehaote(HHHT),Yinchun(YC),Xinin(XN),Lanzhou(LZ),Taiyuan(TY),Shijiazhuang(SJZ),Yantai(YT),Jinan(JN),Xuzhou(XZ),Lianyungang(LYG).The southern cluster consists of the left 16 populations,including Zhengzhou(ZZ),Wuhan(WH), Shanghai(SH),Nanjing(NJ),Hangzhou(HZ),Chongqing(CQ),Nanchang(NC),Wenzhou(WZ),Changsha(CS),Guiyang(GY),Fuzhou(FZ),Kunming(KM),Xiamen(XM),Guangzhou(GZ),Nannning(NN),Hainan(HN).(2) The genetic distances among populations relate to the collection sites to a great extent,though there are some exceptions.According to the facts that we know,(1) D.simulans is an exotic species;(2) The invasion of D.simulans in the mainland of China took place in recent 30 years or so.(3) The widespread distribution of D.simulans in the mainland of China started in recent 10 years or so.Therefore,the results above might not be due to geographical differentiation,but due to genetic differences of initial founder individual(s) between geographical populations.Some of geographically adjacent populations,however,have common initial founder individual(s),which results in the classification of D.simulans populations according to their geographical relationship.We suggest that there are two possible reasons which result in the genetic differences of initial founder individual(s) between geographical populations,one is the D.simulans in the mainland of China had multiple origins,the other is founder effect and/or bottleneck effect that the D.simulans have experienced in the course of expansion.