Researchers find "extinct" oak tree hiding in plain sight

Researchers from The Morton Arboretum and United States Botanic Garden (USBG) have located a lone Chisos Mountain oak, Quercus tardifolia, within the Big Bend National Park in Texas, U.S.A. The rare species has only ever been recorded in the Chisos Mountains in Texas, and in the nearby Sierra del Carmen in northern Coahuila, Mexico. It was first described in the 1930s and the last living specimen was believed to have perished in 2011.

Botanical researchers from 10 different institutions collaborated in the search for a living specimen of the oak tree in its native Chisos Mountains. Their find, although exciting, is also rather disheartening because the 30-foot tree is in very poor condition. Its trunk has been burned in places, and it shows signs of severe fungal infection. It is clearly clinging to life at this stage; a single bush fire or season of drought could mean the end of it.

“This work is crucial to preserve the biodiversity that Earth is so quickly losing,” said Dr. Murphy Westwood. “If we ignore the decline of Q. tardifolia and other rare, endangered trees, we could see countless domino effects with the loss of other living entities in the ecosystems supported by those trees,” she said. According to Westwood, Q. tardifolia is considered one of the rarest, if not the rarest oak in the world.

Scientists are interested in understanding why this species of tree is on the verge of extinction because this knowledge may help to manage other endangered species such that they don’t face the same fate. The group of researchers that discovered the living specimen on May 25, 2022, is now working with the National Park Service to protect the tree from the threat of fires, which have become more prevalent due to climate change. In addition, conservationists will search for acorns from the parent plant and attempt to germinate them, thus propagating new specimens. 

“This is important collaborative research necessary for the conservation of Q. tardifolia,” said Carolyn Whiting, a botanist at Big Bend National Park. “The Chisos Mountains support a high diversity of oak species, partly because of the wide range of habitats available in this ‘sky island.’ There is still much to learn about the oaks in the Chisos.”

“The United States Botanic Garden is thrilled about the success of this partnership and collecting trip that rediscovered such a rare oak,” said Susan Pell, Ph.D., acting executive director at the United States Botanic Garden, which is funding and collaborating on the project. “This discovery is just the beginning of the conservation work we are doing in partnership with The Morton Arboretum to better understand and conserve threatened trees.”

Scientists in the collaborative plan to undertake genetic analysis of the newly-discovered lone tree in order to establish whether its DNA matches that of other specimens collected previously. Oaks tend to hybridize easily, which may allow them to adapt more quickly to changing climate conditions such as extreme heat and new diseases. However, frequent hybridization can blur the genetic lines between oak species in a given ecosystem like Big Bend. 

“This is an interesting problem. We’re looking into whether this tree is genetically similar to other trees that have been previously collected as Q. tardifolia. That should tell us whether this collection is the same as what Cornelius H. Muller named Q. tardifolia. It should also tell us whether this collection of specimens is genetically distinct enough from other, closely related oaks in the area to warrant recognition as a species,” said Dr. Andrew Hipp.

Oaks are unusual among tree species because their acorns cannot survive the usual treatment given to seeds that are stored in seed banks. Acorns do not tolerate being dried and frozen for long periods of time.  Because of this, they must be preserved in the wild or in living collections, which is why the involvement of botanical gardens is critical. The researchers who found the Q. tardifolia tree are concerned that it may not be producing acorns due to its dire condition. If this is the case, then other methods of propagation, including grafting, will be used to preserve the oak’s future.

“Across the planet, oaks serve as an ecological anchor cleaning air, filtering water, sequestering carbon dioxide and supporting countless fungi, insects, birds and mammals,” explained Westwood. “When one is lost, we don’t know what else we might permanently lose in its wake.”

However, Westwood, Pell and others warn that conservation efforts such as this require collaborative initiatives, such as the Global Conservation Consortium for Oak, the involvement of botanical gardens and a variety of scientific experts to secure a future for endangered trees.

“In many ways, this tree is an ancient relic. Due to the changing climate, the world is completely different now than when it evolved,” said Wesley Knapp, chief botanist at NatureServe, who participated in the expedition. “It is incumbent upon us to learn from it and protect it while we still can in order to inform future conservation efforts,” he said. “Nature rarely hands us a second chance, and I doubt we’ll get a third. We won’t waste it.” 

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By Alison Bosman, Earth.com Staff Writer