A FURTHER CONTRIBUTION TO CLOSED-CONE PINE (OOCARPAE) HISTORY

A new record of a fossil Monterey pine (Pinus radiata D. Don) is recorded from rocks of the Plio-Pleistocene age, southern California, and the affinities of other presumed fossil closed-cone pines are revised. This has led to the recognition of two new pine species, Pinus storeyana Axelrod of subsect. Oocarpae and Pinus verdiana Axelrod of subsect. Ponderosae. Geologic evidence indicates that forerunners of the present California and Mexican species of Oocarpae were in proximity in Mexico during the Miocene. They were isolated following opening of the Gulf of California, the northward movement of Baja and Alta California on the San Andreas fault system, and the spread of desert climate. New populations of Pinus radiata developed during the Pliocene (5-2 million years) and later as environmental diversity increased. This also enabled Pinus remorata Mason and P. muricata D. Don, which the fossil record suggests were distinct into the Late Pleistocene, to hybridize in the new topographic-climatic Holocene environments.