Browsing by Subject "Chihuahuan Desert"
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Item Assessing Diet and Seasonality in the Lower Pecos Canyonlands: An Evaluation of Coprolite Specimens as Records of Individual Dietary Decisions(2012-02-14) Riley, TimothyThis dissertation presents an evaluation of coprolite specimens from the Lower Pecos canyonlands as records of individual dietary decisions. Prior studies of coprolites from this region have greatly expanded our knowledge of Archaic subsistence patterns, but have not taken full advantage of the record of individual dietary decisions recorded in each coprolite specimen. The menu, or dietary combinations, reflected in individual coprolite specimens are assessed through the identification of several congruent botanical components derived from the same food resource, phytoliths, fiber ultimates, and epidermal sheets. The data is analyzed with hierarchical cluster analysis, an exploratory statistical technique. The resultant menus reflected in these clusters are evaluated with reference to the diet-breadth model developed for the known staple resources of the canyonlands as well as the seasonal subsistence patterns observed in the ethnohistoric record of modern-day Mexico and Texas. This same technique is also applied to the coprolite data available from previous studies in the Lower Pecos canyonlands. Overall, the combined dietary data available for the Lower Pecos canyonlands presents a similar dependence on desertic plant resources throughout the Archaic. Three main menus are apparent in the specimens. The first menu consists of prickly pear (Opuntia sp.) cladodes, or nopales, and was principally, although not exclusively, consumed in the late spring. This menu is primarily consumed when other resources were not readily available and may be considered a dependable but undesirable meal. The second menu consists of pit-baked lechuguilla (Agave lechuguilla) and sotol (Dasylirion sp.) caudices, or hearts, common throughout the cool season. This menu entails high processing costs, but would provide a reliable caloric return. The third menu exhibits a monolithic reliance on prickly pear fruits, or tunas, during the summer. The ease of harvest and consumption is reflected in the seasonal dominance of this resource, which was assuredly a highly desirable meal. The dietary patterns recorded in the coprolite specimens from the Lower Pecos canyonlands demonstrate a seasonally variable diet-breadth that incorporated low-ranked resources during times of seasonal scarcity as well as a monolithic dependence on high-ranked resources when they were available in the local landscape.Item Evaluation of a Translocated Population of Desert Mule Deer in the Chihuahuan Desert of Northern Coahuila, Mexico(2013-12-10) Ortega-Sanchez, AlfonsoMule deer (Odocoileus hemionus) are large (30?150 kg) ungulates that occur from southern Alaska to the desert mountains, grasslands, and coastal regions of northern and western Mexico. In Mexico, conservation efforts have taken place to reestablish mule deer to their original distribution; however, little information exists on these species. I evaluated post-release movements and vegetation type preferences of translocated desert mule deer in northern Coahuila, Mexico comparing soft- and hard-release as methods of liberation. Translocated mule deer presented difference in dispersal distance from the release site of soft- versus hard- release methods (P = 0.001); however, no difference existed when comparing post-release range sizes of deer released using these methods (P = 0.793). Mule deer habitat was characterized in 3 different classes: creosote flats, lechuguilla hills, and xeroriparian vegetation types. At second order analysis, xeroriparian vegetation type had a higher use/availability ratio (Sxeroriparian = 3.68). At third order habitat selection, 1 of 15 individuals used xeroriparian vegetation type in lesser proportion than its availability (S <1.0) on the upland study area. Six of 15 individuals used xeroriparian vegetation type randomly (S = 1.0?1.1). Eight of 15 individuals used xeroriparian vegetation type in greater proportion than its availability (S >1.1). Translocated mule deer preferred (P = 0.002) to use xeroriparian (9.2% ) greater than their availability (2.5%); use of Lechuguilla hills (63%) presented no difference (P = 0.005) from its availability (64%); and use of creosote flats (25%) was different (P = 0.004) when compared to its availability (34%). Considering the results of my research, I conclude the use of soft-release method is a reliable and successful method for reducing post-release movement of desert mule deer. Although their home ranges may not be reduced in size, translocated mule deer that are soft-released tend to establish their ranges closer to their release site. I provide a guide that describes the options for reintroducing mule deer in the Chihuahuan Desert of Mexico.Item Molecular systematics and the origins of gypsophily in Nama L. (Boraginaceae)(2012-05) Taylor, Sarah Elizabeth; Simpson, Beryl Brintnall; Jansen, Robert K.; Levin, Donald A.; Panero, Jose L.; Mueller, Ulrich G.Nama L. is a genus of approximately 50 species of herbs and subshrubs that occurs in habitats ranging from arid deserts to mesic woodlands in the New World and the Hawaiian Islands. The group has historically been divided into five or six subgeneric groups based on habitat as well as on the morphology of the anthers, styles, leaves and seeds. At least 14 species of Nama from the Chihuahuan Desert Region are either facultatively or obligately endemic to gypsum deposits. This dissertation examines interspecies relationships within Nama from a molecular phylogenetic perspective in order to evaluate historic morphology-based subgeneric classification systems of the genus and to examine the origins of facultative and obligate gypsophily within the genus. DNA sequence data from the chloroplast regions matK and ndhF and from the nuclear ribosomal region ITS were collected from 46 species of Nama as well as from four new species and several outgroups. Data were analyzed using maximum likelihood and Bayesian methods. Phylogenetic analyses recover seven strongly supported major lineages within Nama. These lineages do not correspond to traditionally recognized subgenera, although they are largely congruent with an informal system based on ultrastructural observations of seeds. Four of the seven major lineages include gypsophilous species; these range from two lineages that include a single facultative gypsophile each, to one lineage that is almost entirely comprised of gypsophiles. Gypsum endemism in general, as well as facultative and obligate gypsophily in particular, has arisen multiple times in Nama. Parametric bootstrapping rejected the hypothetical monophyly of gypsophiles across the genus as a whole and within each of the two clades that contain multiple gypsophiles. Because approximately 20 species have been described since the last major revision of Nama nearly 80 years ago, detailed morphological observations of herbarium specimens were made in order to produce a comprehensive key to the species of Nama as well as the revision of a lineage comprising eight gypsophiles and one limestone endemic.