Language: Spanish with bilingual abstract in English and Spanish
A floristic inventory was conducted for the weedy plants occurring in cornfields in the Valley of Morelia, Michoacan, Mexico during the 1993 growing season. Twenty parcels distributed from 1840 to 2560 m above sea level were examined. In each parcel 10 sampling plots, covering a total area of 2.5 m2, were surveyed. The total number of sampling plots was 200. Identification was based on the collection of 3000 specimens.
In total, 189 species belonging to 114 genera and 34 families of angiosperms were identified. Of these, 41 were monocotyledons and 148 were dicotyledons. Compositae (20.10%) were the most diverse among the dicotyledons, whereas Gramineae (14.81%) were the largest for the monocotyledons. These two families contain 34.91% of all species registered, and together with Leguminosae, Euphorbiaceae and Solanaceae, they represent 52.85% of the diversity found.
In comparison with other areas, the weedy flora of the Valley of Morelia is significantly diverse; 11.1% of the species are introduced, mainly from the Old World, while the remainder correspond to plants native to the Americas, principally Mexico and adjacent areas. Sixty-three species, although cited for Mexico as native, are reported for the first time as weeds in cornfields, and almost half of these are restricted to Mexico.