Quercus hinckleyi
Encyclopedia
Quercus hinckleyi is a rare species of oak
known by the common name Hinckley oak. It is native to Texas
in the United States, where it occurs in only two counties. The oak has probably become rare not because of habitat loss, but because today's climate in its native area is too dry. It is federally listed as a threatened species of the United States.
This oak is a shrub
growing into a bushy, tangled thicket not more than 1.5 meters tall. The highly branched stems are coated in scaly gray bark and the smaller twigs are brown and sometimes waxy. The leaves are up to 1.5 centimeters long by 1.5 wide and have large, widely spaced teeth, resembling holly
leaves. The blades are leathery, waxy, and blue-green in color. The fruit is an acorn
1 to 1.5 centimeters wide at the cap, the nut measuring up to 2 centimeters long.
This oak is known from Brewster
and Presidio Counties
in West Texas
. It may also be found just across the border in Mexico. The plant grows in Chihuahuan Desert
scrub habitat on limestone
substrates. The tree grows in very rocky soils or sometimes cracks in solid limestone outcrops.
Climate change
has been implicated as the main reason for the rarity of this plant. It was more abundant 10,000 years ago when this region of Texas was wetter; there are plentiful fossil
ized acorns of this species in rodent midden
s from that era. It may have even been a dominant
species. Low rates of reproduction may also contribute to its rarity. There are about 10 populations in Texas. Most populations are located in Big Bend Ranch State Park
.
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
known by the common name Hinckley oak. It is native to Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
in the United States, where it occurs in only two counties. The oak has probably become rare not because of habitat loss, but because today's climate in its native area is too dry. It is federally listed as a threatened species of the United States.
This oak is a shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
growing into a bushy, tangled thicket not more than 1.5 meters tall. The highly branched stems are coated in scaly gray bark and the smaller twigs are brown and sometimes waxy. The leaves are up to 1.5 centimeters long by 1.5 wide and have large, widely spaced teeth, resembling holly
Holly
Ilex) is a genus of 400 to 600 species of flowering plants in the family Aquifoliaceae, and the only living genus in that family. The species are evergreen and deciduous trees, shrubs, and climbers from tropics to temperate zones world wide....
leaves. The blades are leathery, waxy, and blue-green in color. The fruit is an acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
1 to 1.5 centimeters wide at the cap, the nut measuring up to 2 centimeters long.
This oak is known from Brewster
Brewster County, Texas
Brewster County is a county located in western part of the US state of Texas, along the border with Mexico. It is one of the nine counties that comprise the Trans-Pecos region of West Texas. As of the 2000 census, the population is 8,866. In 2009, the population was estimated to be 9,481. Its...
and Presidio Counties
Presidio County, Texas
Presidio County is a county located in the U.S. state of Texas. In 2000, its population was 7,304. Its county seat is Marfa. Presidio County is in the Trans-Pecos region of West Texas and is named for the ancient border settlement of Presidio del Norte.-Geography:Presidio County is triangular in...
in West Texas
West Texas
West Texas is a vernacular term applied to a region in the southwestern quadrant of the United States that primarily encompasses the arid and semi-arid lands in the western portion of the state of Texas....
. It may also be found just across the border in Mexico. The plant grows in Chihuahuan Desert
Chihuahuan Desert
The Chihuahuan Desert is a desert, and an ecoregion designation, that straddles the U.S.-Mexico border in the central and northern portions of the Mexican Plateau, bordered on the west by the extensive Sierra Madre Occidental range, and overlaying northern portions of the east range, the Sierra...
scrub habitat on limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
substrates. The tree grows in very rocky soils or sometimes cracks in solid limestone outcrops.
Climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
has been implicated as the main reason for the rarity of this plant. It was more abundant 10,000 years ago when this region of Texas was wetter; there are plentiful fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ized acorns of this species in rodent midden
Midden
A midden, is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, vermin, shells, sherds, lithics , and other artifacts and ecofacts associated with past human occupation...
s from that era. It may have even been a dominant
Dominance (ecology)
Ecological dominance is the degree to which a species is more numerous than its competitors in an ecological community, or makes up more of the biomass...
species. Low rates of reproduction may also contribute to its rarity. There are about 10 populations in Texas. Most populations are located in Big Bend Ranch State Park
Big Bend Ranch State Park (Texas)
Big Bend Ranch State Park is a state park located on the Rio Grande in Brewster County and Presidio County, Texas. It is the largest state park in Texas. The closest major town is Presidio, Texas, where the state park's head office is located.-Features:...
.