Floristic affinities of Animas Mountain, Southwestern New Mexico

Animas Mountain of southwestern New Mexico was selected for a floristic inventory and analysis because of the lack of previous study in this unique portion of the Southwest. An annotated checklist of the vascular flora of the study area was compiled. A species-rich flora represented by 718 taxa (ca. 20% of the known flora of New Mexico) was documented by either (i) herbarium specimens from the University of New Mexico, or New Mexico State University herbaria, or (ii) specimens collected during the 1975 and 1976 growing seasons. Floristic assemblages were recognized based upon descriptive field notes, species lists from collection sites, and photographs taken during the collection trips. The vegetation was divided into four community types: (i) grassland, (ii) lower encinal, (iii) upper encinal, and (iv) forest. A distributional analysis was performed on two types of data for each taxon: (i) the fidelity or the degree to which a taxon is restricted to a particular community and (ii) the affinities or the relationship between floras from other physiologic regions in which a taxon is known to occur. The fidelity analysis revealed a striking difference between the low elevational species-rich communities and the high elevation species-poor communities. About 40% of the total species of the lower elevation, grassland and lower encinal communities were restricted to the respective communities, while the high elevational, upper encinal and forest zones only had 9%, and 28% respectively. The grassland had high affinities with the floras of the Great Plains, Sonoran Desert, and central Mexico. Both lower and upper encinal did not have a high percentage of affinities outside of the Southwest and included similarities with the floras of the Colorado Plateau, Trans-Pecos Texas-New Mexico, and southern California. The forest community exhibited similar geographical affinities with the encinal communities, but also showed an affinity with both the Rocky Mountains and eastern North America. The Northern Sierra Madre Biotic Province was defined, based upon a high level of homogeneity of the flora within its boundaries. It extends from southwestern New Mexico to southeastern Arizona southward to northern Mexico. Two types of endemic species were described for the region, those occurring in several localities within the Northern Sierra Madre Province and those from one locality. It is hypothesized that many of these endemic species have evolved since the break-up of the Madro-Tertiary floras, while others were once widespread in the Madro-Tertiary floras but now are restricted to the Northern Sierra Madre Province