Penstemon clevelandii

Photo by: Andrea D. Wolfeİ
Location: San Diego County, California

Penstemon clevelandii picture Penstemon clevelandii is a member of Penstemon subg. Penstemon sect. Peltanthera subsect. Spectabiles (Bennett et al. 1987). It occurs in the cismontane region of southern California and Baja Norte of Mexico. Typical habitats are canyons and roadside cuts in thin, granitic soils from 500 to 1,800 m in elevation. It has a slightly inflated magenta corolla and is visited by hummingbirds and solitary bees.

Several studies of hybridization and hybrid speciation have focused on P. clevelandii (Straw 1955, 1956a,b; Wolfe and Elisens 1993, 1994, 1995; Wolfe et al. 1998a, b). P. clevelandii was proposed as diploid hybrid species with the progenitors P. centranthifolius and P. spectabilis based on morphological and artificial crossing evidence (Straw 1955, 1956a,b). Wolfe and Elisens (1993, 1994, 1995) used allozyme, chloroplast DNA and nuclear ribosomal DNA data to demonstrate that hybrid speciation was not supported, but that introgression of markers from P. centranthifolius to P. spectabilis, P. clevelandii, and P. grinnellii has occurred. More recently, Wolfe et al. (1998a, b) used hypervariable ISSR markers to demonstrate that P. clevelandii is, in fact, a diploid hybrid derivative species.

Bibliography and suggested readings

Bennett, R. W., K. Lodewick, and R. Lodewick. 1987. Penstemon nomenclature. Eugene, OR: American Penstemon Society.

Grant, K. A. and V. Grant. 1968. Hummingbirds and their flowers. New York: Columbia University Press.

Grant, V. 1994. Modes and origins of mechanical and ethological isolation in angiosperms. Proceedings of the National Academy of Sciences, U.S.A. 91: 3-10.

Keck, D. D. 1937. Studies in Penstemon V. The section Peltanthera. American Midland Naturalist 18: 790-829.

Mitchell, R. J. 1988. Is Penstemon centranthifolius truly hummingbird pollinated? Crossosoma 15: 1-9.

Straw, R. M. 1955. Hybridization, homogamy, and sympatric speciation. Evolution 9: 441-444.

Straw, R. M. 1956a. Adaptive morphology of the Penstemon flower. Phytomorphology 6: 112-118.

Straw, R. M. 1956b. Floral isolation in Penstemon. American Midland Naturalist 90: 47-53.

Wolfe, A. D. and W. J. Elisens. 1993. Diploid hybrid speciation in Penstemon revisited. American Journal of Botany 80: 1082-1094.

Wolfe, A. D. and W. J. Elisens. 1994. Nuclear ribosomal DNA restriciton-site variation in Penstemon section Peltanthera (Scrophulariaceae): An evaluation of diploid hybrid speciation and evidence for introgression. American Journal of Botany 81: 1627-1635.

Wolfe, A. D. and W. J. Elisens. 1995. Evidence of chloroplast capture and pollen-mediated gene flow in Penstemon sect. Peltanthera (Scrophulariaceae). Systematic Botany 20: 395-412.

Wolfe, A. D., Q.-Y. Xiang, and S. R. Kephart. 1998. Assessing hybridization in natural populations of Penstemon (Scrophulariaceae) using hypervariable inter simple sequence repeat markers Molecular Ecology 7: 1107-1125.

Wolfe, A. D., Q.-Y. Xiang, and S. R. Kephart. 1998. Diploid hybrid speciation in Penstemon (Scrophulariaceae). Proceedings of the National Academy of Science, USA 95: 5112-5115.

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Last updated September 25, 1998.