木兰科（Magnoliaceae）的起源、进化和地理分布

木兰科为亚洲－美洲间断分布科，全世界有１５属，２４６种，主要分布于亚洲东南部的热带、亚热带地区，从喜马拉雅至日本，向南达新几内亚及新不列颠；少数种类分布于北美东南部、中美至南美巴西．中国有１１属，约９９种．木兰科的现代分布中心在东亚－东南亚地区．根据木兰科的化石记录、系统发育和现代分布，推测其起源时间为早白垩纪，甚至更早．起源地可能在中国的西南地区，并由此向外辐射，向东经日本、俄罗斯远东地区经白令陆桥进入北美；向西经西亚、欧洲，通过格陵兰进入北美，然后到达南美；向南经印度支那、马来西亚，直至新几内亚．东亚－北美间断分布的形成是受第四纪冰期的影响；南美的木兰科是从北美迁移而来．

THE ORIGIN,EVOLUTION AND PHYTOGEOGRAPHY OF MAGNOLIACEAE

Magnoliaceae is a widespread family in tropical, subtropical and warm-temperate regions, especially in East and Southeast Asia, southeast of North America,Central America and the north part of South America.There are 15 genera and about 246 species in the world, 11 genera and 99 species in China. East and Southeast Asia is the centre of recent distribution of Magnoliaceae.According to the evolutionary tendency of the characters and the geographical distribution of this family, we propose a new system by dividing it into two subfamilies, Magnolioideae and Liriodendroideae Law;wo tribes,Magnolieae and Michelieae Law, five subtribes,Manglietiinae Law, Magnoliinae,Alciman driinae Law,Elmerrillinae Law,Micheliinae; and fifteen genera.Based on the evidence of fossil records and modern distribution of Magnoliaceae,it is reasonable to presume that this family1was possibly originated from southwest region of China in very early Cretaceous and radiated from there, and its dispersal routes might be 1. from Southwest China through Japan, Far East of Russia, Bering land bridge, to North America;2.From Southwest China through Old Qinling mountain area,West Siberia, Europe, Greenland, to North America, and then to South America;3.From South China through Indo-China,Malay Peninsula, to New Guinea. The formation of disjunct distribution between East Asia and North America was due to the glaciation during the late Tertiary and Quaternary Periods. Most magnoliaceous plants were extinguished in Europe and the west of North America, with the exception of some plant refuges. The Magnoliaceae in South America was distributed from NOrth America about in Miocene.