ON THE EVOLUTION AND DISTRIBUTION IN SAURURACEAE
1995; Science Press; Linguagem: Inglês
ISSN
0253-2700
Autores Tópico(s)Botany, Ecology, and Taxonomy Studies
ResumoSaururaceae is a small relict family distributed disjunctly between Eastern Asia and North America。 At the present time it only contains 4 genera and 6 species. According to the com- prehensive analysis of the data from cytology, palynology, floral organogenesis and vasculature,embryology,comparative morphology and anatomy,the phylogenetic relationship among the genera of Saururaceae are inferred. The primitive genus Saururus with 2 species is considered much more primitive than the other three genera because it has preserved the probably most prim-itive characters from their ancester. Another Asian genus Gymnotheca with 2 species presents transitional group in the family. Anemopsis is a specialized genus,which is adaptable to the alka-line seasonal xeric place。 Houttuynia is the most advanced taxon in Saururaceae,because it has much more derived characters。Combined the phylogenetic data with the information of palaeogeography,palaeoclimate and fossil record, the origin and formation of distribution of Saururaeeae are discussed。saururaceae is probably originated at the very early Cretaceous period. At that time,Laurasia was still a completed continent and Gondwana land just started to break.The primitive form of Saururaceae may concentrated in south region of Laurasia。The ancestral saururaceae is probalbly similar to the form of nowadays Saururs,a kind of small, rhizomatous perennial herb,with simple flower subtended with bract.During the Cretaceous the climate of southern Laurasia was humid subtropical in general.The primitive genus Saururus thus already completed its disinte-gration and migration in Southern Laurasia,and was belonging to the Late Cretaceous and Early Terliary palaeotropical flora in Laurasia Tethys segregated the way passing to Gondwana。Since Tertiary up to Early Quaternary two differentiation centres developed in Eastern Asia and North America respectively。The modern distribution patterns may be developed as the re-sults of the climate change after the Tertiary Himalayan orogeni movement and the consequence of glacial period during the Late Tertiary and Quaternary. The members of Saururaceae plants become extincted in most parts of Eurasia and North America,but in Eastern Asia and Southeastern America the glaciation was much less heavier,the mesophytic plants were survived in some refugees. At present 75% of total genera and 67% of total species have been collected from Eastern Asia。Obviously this region is the diversifeation and probably origination centres of the family Saururaceae
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