Great Basin Naturalist Volume 46 Number 1 Article 5 1-31-1986 Floristic analysis of the southwestern United States Steven P. McLaughlin University of Arizona, Tucson Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation McLaughlin, Steven P. (1986) "Floristic analysis of the southwestern United States," Great Basin Naturalist: Vol. 46 : No. 1 , Article 5. Available at: https://scholarsarchive.byu.edu/gbn/vol46/iss1/5 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact
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[email protected]. FLORISTIC ANALYSIS OF THE SOUTHWESTERN UNITED STATES Steven P. McLaughlin' Abstract. —A study was made of the distributions of native, terrestrial, \aseular plants occurring in 50 local floras from throughout the Basin and Range and Colorado Plateau physiographic provinces of the southwestern United States. The objectives of the study were to objectively define and describe the floristic elements —assemblages of species with roughly coincident geographic distribution —occurring in the southwestern United States and to deter- mine what such assemblages reveal about the floristic history of the region. The total flora (native, terrestrial species only) of the Southwest is estimated at 5,458 species, 77% of which were recorded in 1 or more of the local floras. Nearly 22% of these species are endemic to the study region. A majority of the species were found to be relatively rare. The average range of a species included only 4 floras, and 90% of the species were recorded from 11 or fewer floras; only 81 species (1.5%) were recorded from 50% or more of the floras.