The Geography of Phytochemical Races

3.2 North American Conifers 153
Fig. 3.9 Map for Bristlecone pine discussion: Pinus aristata (P.a.), Pinus longaeva (P.l.), and
Pinus balfouriana (P.b.)
85.3–98.2% of the monoterpene fraction with the balance comprised of 3-carene
and limonene. Turpentine of P. aristata, however, consisted mainly of 3-carene
with concentrations in the range 62.7–92.1%. Limonene reached a value of 17.9%
in one population with α-pinene ranging between 1.4 and 5.3% at the three sites.
Minor components also contributed to the distinctive chemistries with sabinene,
β-phellandrene, myrcene, and terpinolene regularly present, albeit in small amounts.
These compounds were observed only sporadically, and then only in trace amounts,
in collections of P. longaeva. Running the risk of overstatement, it is useful to point
to the authors’ fi nding that even small differences in the concentrations of camphene
and β-pinene were statistically signifi cant, and that such vivid chemotaxonomic
differences are rarely seen.
With the establishment of clear-cut differences between the two species, the
fi nding of trees from both that deviated widely from their respective population
chemistry takes on special signifi cance. Selected data document these differences
(Table 1 in Zavarin and Snajberk, 1973a). In order to address the problem of inadequate
sample size, the areas were revisited. In the second report from these workers
(Zavarin et al., 1976), the monoterpenes of both wood and foliage of over 200
additional trees were analyzed (including additional P. balfouriana specimens).
These new data fully substantiated the fi ndings of the earlier work, as well as served
to locate additional trees with deviant chemistries. The wood monoterpene profi les
of the northern Arizona population agreed with the earlier fi ndings (normal profi
le), but the newly analyzed foliar monoterpene profi le clearly suggested an intermediate
position between the two species with closer affi nities to P. aristata. The
authors suggested that selection for the present-day chemical profi le has occurred,
but offered no suggestion as to what the selecting factor or factors might have been
that favored particular terpene compositions.