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Group photos Texas OODs
Five days of oaking in the Lone Star State.
Roderick Cameron | Oct 21, 2023
Tour Participants on Fiddler Peak
An account of the Tour guided by Sean Hogan
Website Editor | Oct 19, 2023
Quercus pacifica
An collection specializing in native Californian oaks
Christina Varnava | Oct 18, 2023

Plant Focus

A small but mature Alabama sandstone oak producing acorns © Patrick Thompson
A Critically Endangered dwarf oak 

A Tough Little Survivor: The West Texas Oak, Quercus hinckleyi

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Janet Rizner Backs

Published May 2016 International Oaks No. 27: 75–82


Quercus hinckleyi C.H. Mull. is listed as a threatened species under the U.S. Endangered Species Act and by the state of Texas and is identified as “Critically Endangered” on the IUCN Red List. It has survived over the past 10,000 years in a region in which the climate has become increasingly xeric. Its U.S. range is now limited to a handful of populations in West Texas. Microsatellites were used to genotype ramets collected from three locations in Presidio County, Texas, that represent all known occurrences of Q. hinckleyi to determine genetic variability, population structure, clonal growth, and levels of introgression by two potential hybridizing species.  Genetic diversity for Q. hinckleyi was high and no evidence of inbreeding was found.   Population structure analyses showed two distinct subpopulations with significant differentiation, unique alleles and genetic clustering. High clonality was discovered at the two smallest sites, with only seven unique genotypes among 58 ramets sampled. Sexual reproduction appears to be present at the other sites, as indicated by less extensive cloning. While there is some hybridization, there was no evidence of genetic swamping. The level of genetic diversity and differentiation among the remaining Q. hinckleyi sites warrants protection and preservation of them all.


threatened species, small plant populations, hybridization, clonal growth


Abraham, S.T., D.N. Zaya, W.D. Koenig, and M.V. Ashley. 2011. Interspecific and intraspecific pollination patterns of valley oak, Quercus lobata, in a mixed stand in coastal central California. International Journal of Plant Sciences 172: 691-699.

Backs, J.R., M. Terry, and M.V. Ashley. 2016. Using genetic analysis to evaluate hybridization as a conservation concern for the threatened species, Quercus hinckleyi C.H. Muller (Fagaceae). International Journal of Plant Sciences 177(2): 122-131.

Backs, J.R., M. Terry, M. Klein, and M.V. Ashley. 2015. Genetic analysis of a rare, isolated species: a tough, little West Texas oak, Quercus hinckleyi C.H. Muller. The Journal of The Torrey Botanical Society 142: 4.

Craft, K.J., M.V. Ashley, and W.D. Koenig. 2002. Limited hybridization between Quercus lobata and Quercus douglasii (Fagaceae) in a mixed stand in central coastal California. American Journal of Botany 89: 1792-1798.

Dutech, C., V.L. Sork, A.J. Irwin, P.E. Smouse, and F.W. Davis. 2005. Gene flow and fine-scale genetic structure in a wind-pollinated tree species, Quercus lobata (Fagaceae). American Journal of Botany 92: 252-261.

Kennedy, K., and J. Poole. 1992. HlNCKLEY OAK (Quercus hinckleyi) RECOVERY PLAN. U.S. Fish and Wildlife Service Region 2, Albuquerque, New Mexico.

Muller, C.H. 1951. The significance of vegetative reproduction in Quercus. Madroño 11: 129-137.

Muller, C.H. 1970. Quercus, Manual of the Vascular Plants of Texas. University of Texas at Dallas, Richardson, TX.

Nixon, K.C., R. Jensen, P. Manos, and C.H. Muller. 1997. Fagaceae. Flora of North America north of Mexico 3: 436-506.

Poole, J.M., W.R. Carr, D.M. Price, and J.R. Singhurst. 2007. Rare plants of Texas. Texas A&M University Press, College Station.

Terry, M., and S. Scoppa. 2010. Quercus hinckleyi— Q. vaseyana, A putative hybrid from Presidio County, Texas. Phytologia 92: 400-406.

USFWS. 2009. Hinckley Oak (Quercus hinckleyi) 5-Year Review: Summary and Evaluation. In Trans-Pecos-Sub-Office [ed.], Alpine, TX.

Van Devender, T.R. 1990. Late Quaternary Vegetation and Climate of the Chihuahuan Desert, United States and Mexico. In J.L. Betancourt, T.R. Van Devender, and P.S. Martin [eds.], Packrat Middens: The last 40,000 Years of Biotic Change. Tucson: The University of Arizona Press.

Van Devender, T.R., and W.G. Spaulding. 1979. Development of Vegetation and Climate in the Southwestern United States. Science 204: 701-710.