A comparison of generic endemism of vascular plants between East Asia and North America

Biogeographic interpretations sometimes depend on endemism. The diversity o f endemic genera of vascular plants in different phylogenetic groups was co mpared between East Asia and North America. North America has a significant ly higher diversity of endemic genera of vascular plants than East Asia (98 7 vs. 754 genera). However, East Asia holds greater diversity of endemic ge nera than North America in pteridophytes, gymnosperms, and ranunculids, whi ch are in general evolutionarily old taxa. The two areas do not significant ly differ in the numbers of endemic genera in magnoliids and monocots. The overall diversity bias of endemic genera in favor of North America primaril y results from caryophyllids, rosids, and asterids, which are relatively ad vanced lineages. As a result, numbers of endemic genera within phylogenetic groups do not vary in parallel between East Asia and North America. Compar ed with the world total flora with respect to proportions of numbers of tax a among phylogenetic groups, East Asia and North America both have excesses of endemic genera in asterids and have deficits in magnoliids, monocots, a nd rosids. The most noticeable differences in diversity of endemic genera b etween the two continents were found in pteridophytes, gymnosperms, and ran unculids, for which East Asia shows a striking excess compared with the wor ld flora; North America shows a conspicuous deficit in the first two groups with respect to the world flora. Caryophyllids exhibit a reversed pattern with disproportionately more genera in North America and fewer genera in Ea st Asia compared with the world flora. Differences in diversity of endemic genera between the two continents have resulted from different rates of spe ciation, immigration, and extinction, which have been primarily influenced by land connection, continental drift, geological history, geomorphologic c onfiguration, and climate in the past.