CHEMOSYSTEMATIC STUDIES IN THE GENUS PINUS .7. THE LEAF OIL TERPENE COMPOSITION OF PONDEROSA PINE, PINUS-PONDEROSA

The leaf oil terpene composition of ponderosa pines (Pinus ponderosa Laws.) from 37 sites west of the Continental Divide north of 42-degrees-C, 5 sites east of the Divide in Montana, and 1 each from the Black Hills, South Dakota, Wilkerson Pass, Colorado, and Grand Canyon, Arizona was determined. Tree-to-tree variation was quite low, as was between-population variability at all northwestern locations. Quantitative and qualitative differences in several leaf oil terpenes were found between these and the eastern populations, which lends strong support to the taxonomic separation of ponderosa pine into the typical variety ponderosa and the northeastern var. scopulorum. Intermediate leaf oil terpene compositions were found in several trees near the Continental Divide, indicating that there is a transition between these two varieties. Whereas the Black Hills and Wilkerson Pass samples had terpene compositions that were similar to those of trees from eastern Montana, those from the Grand Canyon area differed quantitatively, indicating that a bridge to the southeastern var. arizonica may be found in the leaf oil composition as well.