The alien flowering plants of Mexico.
A list of 618 species of alien flowering plants recorded for Mexico is presented; they are distributed in 355 genera and 87 families. The families with the largest number of species are Poaceae (171), Fabaceae sensu lato (57), Asteraceae (56), and Brassicaceae (45). The representation of most families with alien species in Mexico agrees with the average distribution frequencies estimated by Pysek (1998) for 26 floras throughout the World. Exceptions are an under-representation of Asteraceae and an over-representation of Poaceae. Most alien species (78.9%) in Mexico have their origin in the Old World; South America ranks second with 9.6%. As defined by Richardson et al. (2000), 19.8% of the alien species could be considered casual aliens and 80.2% of them naturalized. The proportion of alien species relative to the 22 968 native flowering plant species recorded for Mexico is 2.7%.