Revision of the Mexican and Guatemalan Species of Platanus (Platanaceae)

Abstract

A taxonomic treatment of the genus Platanus L. in North America is presented, concentrating on the species native to Mexico and Guatemala. Eight taxa are recognized for North America: 3 species with 2 varieties each, and two species without varietal subdivision; all occur in Mexico and/or Guatemala except for one more northern variety. One previously unrecognized species from western Mexico is described, P. gentryi Nixon & Poole. Another species from northeastern Mexico, although often called P. mexicana Morie., represents an undescribed species because the name P. mexicana is correctly applied to a different Mexican species. The resul- tant new species is P. rzedowskii Nixon & Poole. A new variety, P. mexicana var. interior Nixon & Poole, is described from central Mexico. A key to taxa includes the two Old World species, P. kerrii and P. orientalis, but complete descriptions of the latter species are not given. A discussion of the morphological characters, bio- geography, infrageneric phylogeny and speciation of Platanus in North America is presented in light of the greater understanding of the taxa afforded by this study.