A Pleistocene clone of Palmer's oak persisting in Southern California.
BACKGROUND
The distribution of Palmer's oak (Quercus palmeri Engelm.) includes numerous isolated populations that are presumably relicts of a formerly larger range that has contracted due to spreading aridity following the end of the Pleistocene.


RESULTS
We investigated a recently discovered disjunct population of Palmer's oak in the Jurupa Mountains of Riverside County, California. Patterns of allozyme polymorphism, morphological homogeneity, widespread fruit abortion, and evidence of fire resprouting all strongly support the hypothesis that the population is a single clone. The size of the clone and estimates of annual growth from multiple populations lead us to conclude that the clone is in excess of 13,000 years old.


CONCLUSIONS
The ancient age of the clone implies it originated during the Pleistocene and is a relict of a vanished vegetation community. Range contraction after climate change best explains the modern disjunct distribution of Q. palmeri and perhaps other plants in California.
May
Michael R
MR
Section of Ecology and Evolution, University of California Davis, Davis, California, United States of America.
Provance
Mitchell C
MC
Sanders
Andrew C
AC
Ellstrand
Norman C
NC
Ross-Ibarra
Jeffrey
J
D002140:California; D002999:Clone Cells; D005843:Geography; D011157:Population Dynamics; D029963:Quercus / Q000254:growth & development*; D011891:Rain; D013696:Temperature; D013997:Time Factors