The Geography of Phytochemical Races

3.2 North American Conifers 159
Foliage of Douglas fi r had only trace amounts of (+)-camphene in trees from the
coast but major concentrations in trees from the other three sites. In contrast, terpene
mixtures from lodgepole pine leaf and bole tissues had nearly the same levels
of the major compound, (−)-β-phellandrene, and minor components regardless of
origin. Patterns of variation in the other species were less extreme.
3.2.6 Sequoia sempervirens (Cupressaceae)
Sequoia sempervirens (D. Don) Endl., the coast redwood, is one of the most striking
members of coastal forests of the western United States. The range of the redwoods
extends from southwestern Oregon to the Santa Cruz region of central California.
Although restricted to a strip of coastal North America at the present time, fossil
evidence shows that Sequoia was well developed in the Upper Jurassic and that the
genus enjoyed a wide distribution in appropriate habitats throughout the Northern
Hemisphere. Despite the importance of this species, both from the commercial
forestry standpoint as well as a species of major tourist attraction, comparatively little
work had been done on establishing limits of variation with the apparent exception of
varieties based upon leaf and branch morphology (Dallimore and Jackson, 1966).
In order to rectify this state of affairs, Hall and Langenheim (1987) undertook a
study of monoterpenes of the leaves of redwood collected from sites representing
essentially the entire range of the species. This was done in two ways, sampling of 13
wild populations and sampling of trees grown from seed collected at eight locations
throughout the species’ range and grown and maintained under cultivation for about
20 years at the Russell Reservation, Contra Costa County, California. Fifteen compounds
were identifi ed and quantifi ed as percentages of the total monoterpene fraction.
α-Pinene was the major monoterpene followed, in descending order, by the common
terpenes limonene, sabinene, β-phellandrene, γ-terpinene, and myrcene. The other
identifi ed compounds, α-thujene, camphene, β-pinene, α-phellandrene, α- terpinene,
the cis- and trans- isomers of ocimene, p-cymene, and terpinolene, were present at levels
too low to be of use in numerical analysis. In general, results from analysis of
wild-collected material and cultivated material were in agreement with similar levels
of interpopulation variation which points to the source of variation being genetic rather
than environmental.
Cluster analysis revealed the existence of three groups of populations with a strong
break in the vicinity of San Francisco Bay (Fig. 3.10). Population group 3 occurred
exclusively south of San Francisco Bay, whereas the other two types occur scattered
throughout the northern part of the range of the redwoods. Although the three population
groups exhibited all six marker terpenes, obvious distinctions can be seen, even
with visual examination of the data. Thus, all northern populations, that is, population
groups 1 and 2, exhibited higher levels of α-pinene and β-phellandrene. The
highest levels of limonene, sabinene, myrcene, and γ-terpinene were observed in type
1 populations, although the level of variation among populations was substantial.