TEMPORAL PATTERNS OF TAXONOMIC RESEARCH O N MEXICAN VASCULAR PLANTS AND ESTIMATES OF THE NUMBER OF KNOWN SPECIES

Temporal patterns of research on Mexican vascular plants were analyzed on the basis of counts or estimates of taxa (species and infraspecifi c) described from Mexico since the establishment of the Linnaean syste m (in 1753) up to 1988. Temporal tendencies were found that correlate with known historical events. The cumulative count yielded a total of 23,630 Mexican taxa described in the 235 years of existence of the bin omial system. This number was used as a basis to estimate the number o f taxa known to Mexico up to 1988 using two correction factors: (i) an estimate of the proportion of species that, even though they are pres ent in Mexico, they were not described from that country, and (ii) an estimate of the degree of nomenclatural redundancy (synonymy). With th is method we arrived at a total of 16,870 taxa. Moreover, the curve of the cumulative number of new taxa seems to be far from reaching the a symptote, and over recent years the rate is greater than 150 per year Under the argument that approximately 20% of the total floristic richn ess of the country is yet unknown, we calculate that the number would rise to 20,244, close to Rzedowski's estimate of 22,800. Our estimate, and that of Rzedowski, suggests that the widely cited figure of 30,00 0 species should be taken with caution. Our conservative estimate and the lack of evidence of an asymptote in the rate of acumulation of tax a detected in this study underscore Mexico as one of the territories o f greater Aoristic diversity on the planet.