The Chaparral Vegetation in Mexico Under Nonmediterranean Climate: the Convergence and Madrean-Tethyan Hypotheses Reconsidered1
American Journal of Botany 85(10): 1398±1408. 1998. THE CHAPARRAL VEGETATION IN MEXICO UNDER NONMEDITERRANEAN CLIMATE: THE CONVERGENCE AND MADREAN-TETHYAN HYPOTHESES RECONSIDERED1 ALFONSO VALIENTE-BANUET,2,4 NOEÂ FLORES-HERNAÂ NDEZ,2 MIGUEL VERDUÂ ,3 AND PATRICIA DAÂ VILA3 2Instituto de EcologõÂa, Universidad Nacional AutoÂnoma de MeÂxico, Apartado Postal 70±275, UNAM, 04510 MeÂxico, D.F.; and 3UBIPRO, ENEP-Iztacala, Universidad Nacional AutoÂnoma de MeÂxico, Apartado Postal 314, MeÂxico, 54090, Tlalnepantla, MeÂxico A comparative study between an unburned evergreen sclerophyllous vegetation located in south-central Mexico under a wet-summer climate, with mediterranean regions was conducted in order to re-analyze vegetation and plant characters claimed to converge under mediterranean climates. The comparison considered ¯oristic composition, plant-community struc- ture, and plant characters as adaptations to mediterranean climates and analyzed them by means of a correspondence analysis, considering a tropical spiny shrubland as the external group. We made a species register of the number of species that resprouted after a ®re occurred in 1995 and a distribution map of the evergreen sclerophyllous vegetation in Mexico (mexical) under nonmediterranean climates. The TehuacaÂn mexical does not differ from the evergreen sclerophyllous areas of Chile, California, Australia, and the Mediterranean Basin, according to a correspondence analysis, which ordinated the TehuacaÂn mexical closer to the mediter- ranean areas than to the external group. All the vegetation and ¯oristic characteristics of the mexical, as well as its distribution along the rain-shadowed mountain parts of Mexico, support its origin in the Madrean-Tethyan hypothesis of Axelrod. Therefore, these results allow to expand the convergence paradigm of the chaparral under an integrative view, in which a general trend to aridity might explain ¯oristic and adaptive patterns detected in these environments.
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