Resumo

BALLEZA, José de Jesús; VILLASENOR, José Luis  e  IBARRA-MANRIQUEZ, Guillermo. The biogeographical regions of the state of Zacatecas, Mexico, based on distribution patterns of the family Asteraceae. Rev. Mex. Biodiv. [online]. 2005, vol.76, n.1, pp.71-78. ISSN 2007-8706.

The geographic distribution patterns of 456 species of Asteraceae (Magnoliophyta) native to Zacatecas were analysed. The aim was to propose a state's biogeographic zonation. The state was divided in 28 operational geographic units (OGUs) and for each one the number of species, the number of specimens collected, the vegetation types and the altitudinal range were determined. Floristic similarities among OGUs were obtained by using a classificatory procedure and the Jaccard's similarity coefficient. The richest OGU recorded 190 species of Asteraceae (OGU 28), the poorest 32 species (OGU 5); likewise, the distribution of the species endemic to Mexico varied from 98(OGU 28) to eight (OGU 5 and 6). The OGUs with the larger number of vegetation types and with a larger altitudinal range were also those with the larger number of species. About 34% of the species were considered as rare, because they were recorded in a single OGU. The results suggest that the species of Asteraceae can be divided in two main groups: (i) those thriving mostly in the dry environments characteristic of the Mexican Highland and (ii) those thriving mostly in the temperate and warms habitats found especially along the Sierra Madre Occidental. The analysis identified two biogeographic «districts», forming part of the floristic provinces already defined by Rzedowski (1978).

Palavras-chave : Asteraceae; México; distributional patterns; floristic regions; Zacatecas.