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Cole, Kenneth L

* 1 A classic biogeographic pattern is the alignment of diploid, tetraploid and hexaploid races of creosote bush (Larrea tridentata) across the Chihuahuan, Sonoran and Mohave Deserts of western North America. We used statistically robust differences in guard cell size of modern plants and fossil leaves from packrat middens to map current and past distributions of these ploidy races since the Last Glacial Maximum (LGM). * 2 Glacial/early Holocene (26?10 14C kyr bp or thousands of radiocarbon years before present) populations included diploids along the lower Rio Grande of west Texas, 650 km removed from sympatric diploids and tetraploids in the lower Colorado River Basin of south-eastern California/south-western...
The paleoecological reconstruction of Pleistocene deserts along the Colorado River of western North America is attempted using data from fossil packrat middens. The Colorado River drainage is set into a physiographic context along a gradient from the hyperarid Colorado Desert to the moist high elevations on the Colorado Plateau. The Pleistocene and modern distributions of individual plant species along this corridor are compared emphasizing records from the Picacho Peak area of the Colorado Desert and the eastern Grand Canyon. In general, plant species are now distributed 700?900 m higher in elevation and 400?700 km further up-river than they were during the late Wisconsin, however, some plant species have not conformed...
Aim The geographical extent and climatic tolerances of one- and two-needled pinyon pines (Pinus subsect. Cembroides) are the focus of questions in taxonomy, palaeoclimatology and modelling of future distributions. The identification of these pines, traditionally classified by one- versus two-needled fascicles, is complicated by populations with both one- and two-needled fascicles on the same tree, and the description of two more recently described one-needled varieties: the fallax-type and californiarum-type. Because previous studies have suggested correlations between needle anatomy and climate, including anatomical plasticity reflecting annual precipitation, we approached this study at the level of the anatomy...
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