Population Monitoring and Current Status of Quercus hinckleyi

Phillip Schulze

Published May 2026 in International Oaks No. 37: 339–346

Abstract

Quercus hinckleyi is a Critically Endangered species with a limited distribution in Presidio and Brewster Counties in the Big Bend region of Texas. It is an extreme example of survival under increasingly xeric conditions as they have been occurring across the Southwestern United States for the past 15,000 years. Quercus hinckleyi exhibits strong clonality with plants forming wide multistemmed clumps up to 1 m in height. Although the aboveground stems are rarely more than 2 cm in diameter, they are not young. The individual plants in the clonal clumps are thought to be to be much older and represent what were once larger plants that have died back to their current dwarfed stature. Although acorn production does sometimes occur, no natural recruitment has been documented in situ. The majority of known Q. hinckleyi plants are located within the Big Bend Ranch State Park. Due to the inaccessibility and harsh conditions of these locations, population monitoring studies have not previously been conducted. The Lady Bird Johnson Wildflower Center is conducting a multi-year population monitoring study to characterize the current status of this population, determine threats to survival and reproduction, and potentially harvest acorns for ex-situ conservation. The Wildflower Center has mapped the location of plants throughout the park, focusing on a sub-population of approximately 130 individual clumps for detailed monitoring. In the fall of 2024, each plant within this study area was mapped, with documentation of height, diameter, condition, herbivory incidence, and presence or absence of acorns.

Keywords

Chihuahuan desert, shrub oak, endangered species

References

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