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Listado florístico de la cuenca del río Balsas, México

1998; Escuela Nacional de Ciencias Biológicas; Issue: 9 Linguagem: Inglês

2395-9525

Rafael Fernández Nava, Concepción Rodríguez Jiménez, Marìa de la Luz Arreguín Sánchez, Adela Rodríguez Jiménez,

Plant and soil sciences

The Balsas river basin is one of the largest and most important in Mexico. Comprising approximately 112,320 km, it forms an eastwest-oriented depression in central-south Mexico and occupies portions of the states of Guerrero, Jalisco, Mexico, Michoacan, Oaxaca, Puebla, and Tlaxcala, and all of Morelos. The basin is physiographically delimited by the Transverse Volcanic Belt to the north and the Sierra Madre del Sur to the south, and lies between 17°00' and 20°00' N latitude and 97°30' and 103°15' W longitude. The prevailing climate is warm and semiarid, with the aridity increasing eastward, where most of the xerophytic elements are thus concentrated. Due to its position between two major mountain chains and the resultant variations in elevation within the area, various and diverse vegetation types occur in the region, ranging from xerophyllous scrubs to tropical forests to oak-pine forests and even alpine grasslands above treeline. The great diversity of environmental conditions that characterize the Balsas river basin, as well as the biotic relationships to the neighboring areas, which belong to quite separate floristic regions, confer a great floristic diversity to the area. The existing information on the vegetation and flora of the basin is not extensive, and we therefore can consider this to be one of the more poorly known regions of Mexico from the botanical point of view. The principal objective of this work is to present a preliminary list of the phanerogamic flora of the balsas river Basin, based on the species that have been collected in or cited from the area. The list is alphabetical by family, genus, and species within the major groups of pteridophytes, gymnosperms, and angiosperms. The list includes 202 families, 1,246 genera and 4,442 species. The largest families are: Compositae with 136 genera and 573 species, Leguminosae with 90 genera and 486 species, Gramineae with 84 genera and 253 species and Orchidaceae with 51 genera and 197 species. The best collected states within the basin at present are Guerrero, Michoacan and Morelos.