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Physiological differences between two Penstemon species and
their hybrids
in a natural hybrid zone


Piute Pass and Tioga Pass Transects, Eastern Sierra, California

Kimball, S. & D.R. Campbell. In press. Physiological differences between two Penstemon species and their hybrids in field and common garden environments. New Phytologist.
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Links to Penstemon Research Topics:
Dissertation Summary


Reproductive Isolation

Links to Additional Research Topics:

Traits influencing plant community composition

Restoration ecology at Carrizo Plain National Monument

Local ecology and geographic range limits





Hybrids can exhibit unique combinations of parental traits through recombination. Such unique combinations of physiological traits may influence hybrid fitness and the evolutionary trajectory of a hybrid zone.

We examined a hybrid zone between Penstemon newberryi and P. davidsonii along an elevational gradient in the eastern Sierra Nevada, CA, measuring traits of parents and hybrids in their native environment and in a common garden.

We measured stem water potential, specific leaf area, phenology, and gas exchange rates of both species and naturally occurring hybrids. We also measured gas exchange rates on seven different hybrid crosses as well as the two pure parent species.

Alpine P. davidsonii had less negative pre-dawn and mid-day water potential, and lower water-use-efficiency than its montane relative, P. newberryi. The alpine species also took less time to produce mature fruits. Hybrids were intermediate for most characters, but gas exchange traits differed depending on the genetic background of the hybrid.

Physiological differences between parents and hybrids may vary depending on the genotype of the hybrid and on environmental conditions.

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