PRESENCIA DETAXUS GLOBOSASCHLECHT. (TAXACEAE) EN EL ESTADO DE CHIAPAS, MEXICO

Taxus globosa Schlecht. (Taxaceae) isreported for the first time for the flora ofthe Mexican state of Chiapas, fromspecimens revised in the following herbaria:MEXU, FCME, and CHAP.Se registra por primera vez para la flora delestado de Chiapas a Taxus globosaSchlecht. (Taxaceae), a partir deespecímenes revisados en los herbariosMEXU, FCME y CHAP

Historical relationships of the Mexican cloud forests: a preliminary vicariance model applying Parsimony Analysis of Endemicity to vascular plant taxa

Abstract Mexican cloud forests, situated between 600 and 3000 m of elevation, exhibit a remarkable high biotic diversity. They follow a fragmented pattern, similar to that of an archipelago, that makes them suitable to vicariance modelling. A Parsimony Analysis of Endemicity (PAE) was applied to the presence/absence of 1267 species of vascular plants (gymnosperms, angiosperms, and pteridophytes) from twenty-four patches of Mexican cloud forests, in order to postulate a preliminary hypothesis of relationships. The single cladogram obtained grouped the twenty-four cloud forests into five clades. These results indicate that the Sierra Madre Oriental, Sierra Madre del Sur, and Serranías Meridionales floristic provinces do not represent natural units. A preliminary vicariance model is presented to explain the sequence of fragmentation of the Mexican cloud forests

Historical biogeography applied to the distribution of Mexican plants

Biogeographical patterns of the Mexican flora are explained based on 3 different theories, considering number of species, endemisms, and relations among areas: 1) dispersalist theory, where Mexico has been considered as the receiver of elements of different sources or geographic areas, considering that it is located in the transition zone between the Nearctic and Neotropical regions, which along the autochthonous ones form a complex mixture of species with different origins, both spatial and temporal, 2) vicariant theory, that proposes a close relationship between the earth's history and the history of the biota, so that the number of species and their distribution may be explained by the complex geologic history of Mexico, and 3) pleistocenic glaciations, which explain the recent distributional patterns of plants based on ecological and historical arguments, based on paleoclimatic changes of the recent past. A continuous debate within historical biogeography has high lighted the importance of biogeography as source of evidence for taxonomy and vice versa. Historical biogeography has a close relationship with systematics, but is an independent discipline within comparative biology. Biogeography is undergoing a conceptual revolution that is causing a revision of its fundamentals and methods. The utilization of different methods in an integrative manner in the same analysis may maximize the advantages of each one