One of the world’s oldest plants turns out to be a 13,000 year-old scrub oak (Quercus palmeri, or Palmer’s Oak) in Southern California. Apparently this tree has survived for so long, despite the fact that it was born in the ice age and there have been numerous climate changes since then, by cloning itself, hiding in a crevice, being small, and growing slowly. Luck was involved as well, almost certainly.
The plant was actually discovered more than ten years ago during a survey of plant diversity in the Jurupa Hills of Riverside County, and it was noted at the time that this tree was utterly out of place. According to Jeffrey Ross-Ibarra, a professor at the University of California Davis,
Palmer’s Oak normally occurs at much higher elevations, in cooler, wetter climates. In contrast, the Jurupa Oak scrapes by in dry chaparral, wedged between granite boulders and stunted by high winds, atop a small hill in plain sight of suburban backyards.
You never know what you are going to find in your backyard in the suburbs of California.
The age of the tree was estimated by an analysis of the rings by Michael May.
Ring counts show that the Jurupa Oak is growing extremely slowly. At its current rate of about 1/20th of an inch per year, it would have taken at least 13,000 years for the clone to reach its current size. And it could be much older.
There are actually several pockets of this species of tree located outside the plant’s main distribution, and reproduction by cloning seems to be the modus operands for their long term survival.
The researchers believe that
…this stand of Q. palmeri is a relict of an ancient population that has persisted in the Jurupa Mountains despite warming since the last glacial period. … ancient clones have been identified in other woody taxa , including a nearly 12,000 year old clone of creosote (Larrea tridentata Coville) found in the Mojave Desert. Nonetheless, our 13,000 year estimate for the age of the Jurupa clone places it among the oldest of living plants.
… Our findings at Jurupa suggest that cloning may be a significant contributor to the persistence of these disjunct populations. Numerous other woody shrubs in the southwest share such disjunct distributions and patterns of growth, and it is thus tempting to speculate that disjunct populations of many of these other species may consist of extremely long-lived clones as well.
Some day the Ice Age will be back, and perhaps these lower elevation pockets of self-cloning plants will contribute to the inevitable shift in the distribution of vegetation. Should they survive global warming, that is.
The paper that reports these findings is published in PLoS ONE, an OpenAccess science journal. This means that you can read the original paper even though you are not a subscriber. That is how OpenAccess works.
May, M., Provance, M., Sanders, A., Ellstrand, N., & Ross-Ibarra, J. (2009). A Pleistocene Clone of Palmer’s Oak Persisting in Southern California PLoS ONE, 4 (12) DOI: 10.1371/journal.pone.0008346