Especies exóticas de la vertiente occidental de la cordillera de la Costa, Provincia de Valparaíso, Chile central

central chile supports a rich native fora and a high proportion of alien, naturalized plants. to increase our knowledge about behavior of naturalized plants in central chile, the fora of the western slope of the coastal range (province valparaiso, 33°s lat.), was recorded and analyzed. study sites were placed at natural and anthropic, perturbed areas. taxonomic richness, species composition, geographic origin, raunkiaer？s life forms, and absolute coverage were recorded. of the 325 vascular plant species were identifed, 110 (34%) were considered alien; 74% of them with european origin, and 10%, european-north african. according to abundance, 27 % of the plant coverage was of native species and 73% of non-natives. the natives were distributed in 68 families and the naturalized and cultivated in 28 families. asteraceae, poaceae y fabaceae were the richest in both native and naturalized species. the native species were distributed in 146 genera and non natives in 89. alstroemeria, baccharis and calceolaria were the richest in native species; erodium, trifolium, rumex and vicia, were rich in alien species. hemicryptophytes and therophytes were most abundant in natives and naturalized species. we conclude that due to increasing urban and agricultural pressures on soils in province valparaíso, it is expected that short-lived alien species with opportunistic, high-reproductive capacity, will increase in diversity and abundance.