California Native Plant Society
Santa Cruz County Chapter

General Meeting
Monday September 10
Keying Club 5:30 pm
Presentation 7:30 pm

UCSC Arboretum Horticulture Building
1156 High Street, Santa Cruz

The evolution and diversification of the red oaks (Agrifoliae)
of the California Floristic Province

Al Keuter
Just a regular guy who became interested in California red oaks

Agrifoliae: the native California red oaks Only 4 species but often very difficult to identify because of gene flow among them.

A 2017 paper published in the American Journal of Botany reported that a useful approach to understanding the relationships and evolution of the California red oaks was to combine old-fashioned morphological measurements with modern cutting-edge DNA analysis. A brief review of the paper will (hopefully) provide a better understanding of the Agrifoliae.

Since 2013, Al has made 785+ collections of vegetation and fruit from more than 450 red oaks in 31 California counties and has documented the collections in more than 20,000 photographs, micrographs, and high-resolution scanned images.

Al was one of the five authors of the paper "The evolution and diversification of the red oaks of the California Floristic Province (Quercus section Lobatae, series Agrifoliae)," (American Journal of Botany, 2017), and more recently published "Observations of hermaphroditic late-season flowering in the red oak Quercus agrifolia" (Phytoneuron, 2018).


Of the two varieties of Q. agrifolia (var. oxyadenia, sharpacorn oak, below, left; var. agrifolia, coast live oak, below, right), the southern California variety is not well known to many northern California botanists.

oxy-ag comparison

Typical specimens of Q. parvula var. shrevei (left, below) and Q. wislizeni (right, below, same scale), are not too hard to tell apart, right? Less typical specimens can be difficult to identify.

parv-wis comparison