Diversity and Origin of the Central Mexican Alpine Flora

Alpine vegetation is scarce in central Mexico (≈150 km2) and occurs on the 11 highest peaks of Trans-Mexican Volcanic Belt (TMVB). Timberline at (3700) 3900 m, 4750 m vascular plants cease to exist. The alpine flora comprises 237 species from 46 families 130 genera. Asteraceae (44), Poaceae (42), Caryophyllaceae (21) possess 45% species; none remaining have more than 10 species. Four are strict endemics, eight others near endemics. Thirteen restricted but also occur outside study area. Seventy-seven endemic Mexico, 35 which TMVB. In terms biogeography, strongest affinities with Central or South America. Fifteen native Old World. Size area seems not be determining factor for its floristic diversity. Instead, time since extent last volcanic activity, addition distance other islands, appear important factors affecting There evidence upward vegetational shifts having occurred during century.