The Geography of Phytochemical Races

2.7 North and Central America 101
Plants were collected along an east-west transect lying at approximately 40°40 N
in the southern Rocky Mountains of Colorado, and represented sites that ranged
from 1598 to 3568 m (Bowman, 1983). The compound with 33 carbons was the
major alkane in all samples with the C 31 compound next in abundance. Clustering
of the Sedum populations on the basis of alkane proportions showed, for example,
that the nearest neighbors based upon total alkane variability were two populations
that occupied elevational extremes. In other instances, nearest neighbors along the
transect were nearly identical, which was taken to indicate the possibility of “clonal
propagation or localized biotypes.”
2.7.11 Delphinium variegatum (Ranunculaceae)
Another example of variation on a local scale in southern California comes from the
work of Dodd and Helenurm (2000) on Delphinium variegatum Torrey and Gray
(Ranunculaceae), an attractive larkspur native to grasslands and open woodlands
throughout its range. This species is thought to consist of three subspecies, subsp.
Variegatum, which occurs exclusively in central California from the coast to the
foothills of the Sierra Nevada, and two that are endemic to San Clemente Island,
subsp. kinkiense (Munz) M. J. Warnock and subsp. thornei (Munz) M. J. Warnock.
Three features distinguish the two insular taxa, lateral sepal length, lower petal
blade length, and sepal color, which range from white through pale to dark blue. So
far, no chemical study has been done on the pigment(s) of this species of larkspur,
but it seems a fair guess that glycosides of delphinidin are involved. Depth of color
may simply be the result of greater concentrations of pigment in certain lines, or
there could be a more complicated explanation based upon the known capacity of
blue pigmentation to involve intricate complexation of the fundamental anthocyanin
with metallic ions. White, of course, can be taken to indicate the complete absence
of part, or all, of the anthocyanin biosynthetic pathway.
Neither metric character sepal length nor petal length can be used to distinguish
between the two subspecies on San Clemente Island. Sepal color provided somewhat
better separation, but the distribution of pigmented individuals was not clear-cut.
Seven of the eight northernmost populations had white or pale blue fl owers; the
eighth had a small fraction of darker blue fl owers. Populations in the central part
of the island had varying fractions of pale, intermediate, and dark fl owers, whereas
as the majority of populations in the southern part of the island have predominantly
dark fl owers, but almost always with some fl owers of lighter hue. The southernmost
population, with primarily white or pale fl owers, resembles populations from
mid-island. Dodd and Helenurm (2000) speculated that the “problem” may reside in
sampling and in the nature of the specimens studied, primarily herbarium material
in the taxonomic study (Warnock, 1990a, b) compared to the extensive population
sampling of the present work. In short, the more one looks, the more one may fi nd.
The authors went on to suggest that subspecifi c recognition may not be justifi ed,
suggesting rather that varietal status may be more appropriate, but added that further