XVI International Botanical Congess

Species composition of 109 trans-Pacific disjunct genera was compared. E. Asian flora contains about 1/3 more species than that of N. Am., the difference in disjunct taxa is less. Woody genera exhibit a strong diversity bias favoring e. Asia whereas there is no difference in diversity in herbaceous genera. On both continents, woody genera were distributed in lower latitudes than herbaceous genera and both woody and herbaceous genera were distributed in lower latitudes in e. Asia than in N. Am. The N. Am. flora is primarily a relict of a flora formerly more widespread in the northern hemisphere, and contemporary patterns of diversity suggest that climate changes in the late Tertiary promoted diversity in e. Asia but caused extinction in N. Am. The floras of both regions bear the imprint of history and the interface between ecological relationships and evolutionary responses.