Biogeography

Abstract

A phytochemical analytical study was conducted to address the question of whether Lophophora williamsii (peyote) plants from Chihuahuan Desert populations in the Trans-Pecos region of West Texas exhibited higher tissue concentrations of mescaline than plants from Tamaulipan Thornscrub populations of South Texas. This question is of cultural significance to the Native American peyote religion, which involves the ingestion of peyote as a psychopharmacologically active sacrament. Tissue samples were field-collected from 10 individuals in each of four L. williamsii populations, two of which were located in the Chihuahuan Desert, and two of which were located in the Tamaulipan Thornscrub ecoregion. For each of the four populations, the tissue samples from 10 individual plants were pooled, the alkaloids were extracted, and the average mescaline concentration of the population was determined by HPLC. There was limited geographic variation in mescaline concentration; the highest concentration (3.52% of dry tissue) was only 27% greater than the lowest (2.77%), and the difference between the Chihuahuan Desert populations and the Tamaulipan Thornscrub populations was not significant. However, mescaline concentrations increased significantly along a gradient from southeast to northwest, i.e., from the southeasternmost Tamaulipan Thornscrub population to the northwesternmost Chihuahuan Desert population. 

Abstract

The Dead Horse Mountains of Big Bend National Park are one of the least explored areas in Texas. This is the first collective body of work to document the area's vascular flora through a major new collection of vouchered specimens and a survey of existing herbarium specimens. Field work was performed between August 2003 and September 2006. The study area covers 176,800 acres (71,548 hectares; 276 mi², 715 km²) with a 4100 ft (1250 m) range in elevation. Non-vascular specimens (bryophytes, hepatophytes, and lichens) were also collected but not included in the final analysis. A total of 1584 vascular specimens were collected during the current study; a herbaria search uncovered 2212 previously-collected vouchers. The flora consists of 662 species in 344 genera and 91 families. The best-represented families are the Asteraceae (80 species), Poaceae (75 species), Fabaceae (52 species), Euphorbiaceae (34 species), Cactaceae (34 species), Pteridaceae (20 species), and Boraginaceae (20 species). Seymeria falcata var. falcata was collected for the first time in the United States while eight new species were recorded for Brewster County. One additional taxon (Galactia sp.) may be undescribed or new to the United States. Vouchered taxa increased by 12% and 55 species were documented in the study area for the first time. Twenty-four non-native species are known from the study area; three are state-listed noxious weeds, and six are considered invasive. The number of known Texas endemics in the Dead Horse increased to 11; seventeen species are considered rare. The Dead Horse flora differs from other southwestern floras mainly by an increased relative importance of monocots, and the elevation of the Poaceae to be co-dominant with the Asteraceae. These and other factors suggest connections to several peripheral floristic areas, ranging from the Mogollon Rim and the Great Plains to South Texas and southern Mexico.

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