One of the most fascinating aspects of angiosperm biogeography in the Northern Hemisphere is the intercontinental disjunct distribution of closely related species. Analyses of phylogenetic relationships and divergence times are crucial in seeking possible explanations for the origins of various disjunct patterns. Molecular phylogenetic analyses of diverse plant taxa with clades disjunctly distributed in eastern Asia, eastern North America, western North America (e.g., Trillium, Cornus , Boykinia , Tiarella , Trautvetteria , Thermopsis , Aralia sect. Aralia , Calycanthus , Asarum , Staphylea ), and taxa also found in one or more of the following areas: Europe, western Asia, and South America in addition to eastern Asia and North America (e.g., Aesculus , Chrysosplenium , Gleditsia , Styrax , Astragalus , Nuphar , and Rubus ) revealed similar phylogenetic patterns: the North American species form a monophyletic group sister to the eastern Asian or the Eurasian species, with the old world species basal and the South American species appearing in derived positions. Vicariance-Dispersal analyses suggested that 1) many taxa diversified in eastern Asia and then spread from the old-world to the new-world; 2) The modern disjunctions are mostly the result of vicariance following dispersal and geographical isolation; 3) vicariance events within North American or Eurasian continent occurred subsequent to that between the two continents; and 4) disjunct distributions in South America are due to long-dispersal from North America or from eastern Asia. Analyses of divergence times using molecular clocks indicated that disjunct species from different genera diverged at different geological times (Oligocene to recent) with most of the eastern Asian-eastern North American species analyzed diverged from the late Miocene to the Quaternary. These data suggested that the congruent geographic distributions and phylogenetic pattern exhibited by these disjunct taxa represent "pseudocongruence".

Key words: angiosperms, disjunct taxa, divergence time, historical biogeography, Northern Hemisphere, phylogenetic pattern