The Distribution, Synonymy, and Taxonomy of Three Junipers of Southwestern United States and Northern Mexico

Abstract

Revised distribution maps, new keys, and updated synonymy are presented for Juniperus erythrocarpa, J. monosperma, and J. pinchotii. These revisions reflect the authors' evidence from the past several years and are presented to aid field workers in the identification of these difficult taxa. The one-seeded junipers of the southwestern United States and northern Mexico have been both confused and confusing for many years. Previous to the work of Adams and Zanoni, the only taxonomic treatments dealing with the taxa were those in the manuals and floras of the states involved (Correll 1966, Correll and Johnston 1970, Kearney and Peebles 1951, McDougall 1973, Wooton and Standley 1915). The two taxa recognized were Juniperus monosperma (Engelmann) Sargent and J. pinchotii Sudworth. Although Cory (1936) recognized a third taxon, J. erythrocarpa Cory, in Texas, subsequent floras and checklists for Texas (Correll 1966, Correll and Johnston 1970, Gould 1975) relegated J. erythrocarpa to synonymy under J. pinchotii. Concurrently, however, Martinez (1946, 1953, 1963) accepted the usage of J. erythrocarpa (as J. erythrocarpa var. coahuilensis Martinez) for plants in Mexico. Van Melle (1952) further confused the issue by naming the bright red fruited form of J. pinchotii from the Chisos Mountains as J. texensis. Adams (1975) found no evidence for J. texensis and found only J. pinchotii and J. erythrocarpa in the Chisos Mountains (although hybridization between these two taxa seems likely). It appears that the bright red fruited plants (J. texensis) are either a form of J. pinchotii or perhaps backcrossed individuals from J. erythrocarpa with J. pinchotii. Adams (1972, 1975) and Zanoni and Adams (1975, 1976), in analyses of J. pinchotii and of the taxa in Mexico, recurrently dis-