The Geography of Phytochemical Races

3.2 North American Conifers 151
dissection of the species. A brief review of studies documenting racial, ecotypic,
and altitudinal variation can be found in the introduction to the chemosystematic
work of von Rudloff and Lapp (1991). In addition to those sources of information,
the reader may wish to consult a comprehensive listing of literature published on
ponderosa pine up to 1965 compiled by Axelton (1967).
Of interest to us here is the chemical study by von Rudloff and Lapp (1991), who
examined the leaf oil composition of trees from 37 northwestern sites, with eight
of these representing the northeastern variety (scopulorum), and a single specimen
representing var. arizonica. In addition to the dozen identifi ed compounds, several
unknowns (homogeneous by GLC analysis), two sets of isomers, and several minor
components were reported. Although there was some overlap in the ranges of values
for most of the compounds observed, overall differences are evident. Within
the major components, β-pinene was present in 40–63% relative amounts in var.
ponderosa as opposed to 32–45% in var. scopulorum. Similarly, α-pinene was present
in 8–18% and 15–26% and estragole (p-methoxyallylbenzene, 118) was present
in 1–21% and trace—6% in var. ponderosa and var. scopulorum, respectively. Several
minor components, including limonene, ocimene, and camphene, tended to be
present in higher concentrations in eastern trees. There was also a tendency for trees
along the Continental Divide to exhibit terpene profi les of somewhat more intermediate
composition, with some components present in concentrations more typical of
“western” trees while others resembled “eastern” profi les. Thus, this area appears to
be an area of transition between the two varieties. Although only one specimen of
var. arizonica was studied, the differences observed suggest that major differences
exist relative to the northern varieties. Thus, whereas the northern varieties featured
β-pinene as the major oil component (total range 32.0–63.0%), this compound was
present in only 18.4% in the specimen of var. arizonica. The major component of oil
from var. arizonica was α-pinene at 37% as compared to the total range of 8.0–26%
for the northern varieties. Other compounds that were present in levels higher than
seen in the northern varieties include limonene and linaloöl. Given the obvious limitations
placed on these conclusions because of the sampling, it would seem a reasonable
hypothesis to suggest that the terpene profi le of var. arizonica more closely
approximates that of var. scopulorum than it does to that of var. ponderosa.
Pinus monticola Dougl., the western white pine, occurs in the coast ranges of British
Columbia south through the Cascade Mountains of Washington and Oregon, and in the
Sierra Nevada, and in a second band in the Rocky Mountains of British Columbia south
through northern Idaho, and western Montana, and in the mountains of northeastern
Oregon. An earlier chemical study of specimens from 20 sites in British Columbia,
Washington, and northernmost Oregon and Idaho showed little geographical patterning
of foliar monoterpenes (Hunt and von Rudloff, 1977). Hanover (1966b) studied the
genetic control of monoterpene levels in this species of pine.
In order to expand the chemical sampling of this species to its entire range and to
investigate xylem terpenoids in detail, Zavarin et al. (1990) collected wood samples
from 191 trees from 20 areas, isolated the monoterpene fractions, and subjected
them to GLC analysis. The major component was identifi ed as α-pinene, with
β-pinene, 3-carene, and limonene as lesser, but still important, components. Minor