一些东亚特有种子植物的化石历史及其植物地理学意义

特有植物在植物区系地理的研究中有重要意义,不同等级的特有植物往往成为不同等级植物区系分区的重要依据。查明东亚特有植物的地史渊源对于揭示东亚植物区的特征与性质,理解中国植物区系及东亚植物发生和演变都有重要的意义。本文在现有资料的基础上,分析总结了东亚植物区系中有化石记录的银杏科、杜仲科、连香树科、大血藤科和昆栏树科等5个特有科,水杉等21个特有属的化石历史。从这些特有植物化石历史的分析可以发现,东亚植物的特有植物从来源上可以分为北极-第三纪,北热带,和就地起源等3种类型,特有植物的来源表明东亚植物区系是一个来源复杂的植物区系。尽管各种特有类群的地质历史各不相同,但是都经历了从广布到分布区逐步缩小,最后形成特有的过程。大部分特有类群形成特有的时间是在上新世末到第四纪初。根据特有类群划分区系等级的原则,东亚现代植物区系最终形成的时间应该是上新世末到第四纪初。

Fossil History of Some Endemic Seed Plants of East Asia and Its Phytogeographical Significance

Endemic elements are crucial for floristic and phytogeographical analysis . The levels of ende-micity are important foundation of dividingfloristic regions , different floristic ranks based on different en-demic levels . The fossil history of endemic families and genera tothe East Asia Floristic Kingdomplay animportant role in understandingthe origin, development and differentiation of thisflora kingdom. The fos-sil history of five endemic families (Cercidiphyllaceae , Eucommiaceae , Ginkgoaceae , Sargentodoxaceaeand Treochodendraceae) and 20 endemic genera (Cathaya,Cephalotaxus,Corylopsis,Craigia,Cun-inghamia,Davidia,Dipteronia,Emmenopterys,Exbucklandia,Fokienia,Fortunearia,Glyptostro-bus,Keteleeria,Metasequoia,Pseudolarix,Platycarya,Shaniodendron,Sinowilsonia,Tapiscia,ToricelliaandTaiwania) are reviewed. The fossil history shows that these endemic plants have three re- sources, one from Arctic-Tertiary, one boreotropic and one East Asia . This indicates that East floristiccombination are a complexinits origin. Above mentionedthree elements would be their three of resourc-es . All endemic plants had much wider distributions in geological time . Their distributions were reducedduringlong geological time and become endemic to East Asia inthe late Pliocene or early Quaternary. Ifthe levels of endemismare reallyimportant foundationfor dividingfloristic regions ,thetime of formation ofendemicity would be the time of formation of the floristic regions . The modern East Asia plant kingdomwould be formedinthe late Pliocene or early Quaternary.