VASCULAR PLANT DIVERSITY IN EASTERN ASIA AND NORTH-AMERICA - HISTORICAL AND ECOLOGICAL EXPLANATIONS

Taxonomic diversity of vascular plants (ferns, gymnosperms and angiosp erms) was compared between eastern Asia and North America. Eastern Asi a has significantly higher species richness in all three classes but t he difference was greatest in ferns and least in angiosperms. Differen ces in taxonomic treatments between the two continents are not likely contributors to these patterns. The relationship of regional to global species richness across the three plant classes suggested that divers ity patterns were relatively homogeneous at: three taxonomic levels. T hus, differences in species richness are established at the family lev el and are therefore relatively old. The previously noted fact that ea stern Asia has a higher proportion of primitive taxa was shown by anal yses both among and within plant classes. Diversity patterns across th ree taxonomic levels (i.e. family, genus and species) of the three cla sses may reflect the relative historical positions of the two continen ts (following continental drift) to the centre(s) of their origin, nei ghbouring land masses, differential speciation/extinction rates, and s witches in dominance levels associated with climate change (including glaciation), as well as reproductive/dispersal mechanisms of the three plant classes. (C) 1998 The Linnean Society of London.