Kimball, Sarah , Campbell, Diane R. .
Physiological Differences Maintain Species in a Natural Plant Hybrid Zone.
OCCUPATION of separate habitats could limit the hybridization of closely related plants. Such habitat limits are potentially determined by climate and physiological traits. We examined a hybrid zone between Penstemon newberryi and P. davidsonii along an elevational gradient in the eastern Sierra Nevada, CA. We measured temperature and relative humidity along the elevational gradient to characterize different habitats. To determine which physiological traits may determine elevational range limits, we measured water potential, foliar ? 13C, % C, ? 15N, and % N, SLA, phenology, and gas exchange rates of both species and naturally occurring hybrids. Measurements were taken along two elevational transects in the field and on plants grown in pots. Alpine P. davidsonii had lower water potential, lower WUE, and lower Amax than its montane relative, P. newberryi. The alpine species also took less time to produce mature fruits. Hybrids were intermediate for most characters. Physiological differences may be responsible for maintaining the parent species as distinct entities despite high levels of hybridization in zones of range overlap.
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1 - University of California Irvine, Department of Ecology & Evolutionary Biology, 321 Steinhaus Hall, Irvine, California, 92697-2525, USA
geographic range limits
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, August 1st, 2006
Time: 9:15 AM