The Geography of Phytochemical Races

2.7 North and Central America 89
those studies however, which prompted an examination of a larger number of individuals
from as many of the species’ respective ranges as possible.
The presence of variable pigment profi les in several other species was noted in a
survey of populations (Saleh et al., 1971; Ornduff et al., 1974) and on a study of fl avonoids
of artifi cial hybrids in the genus (Ornduff et al., 1973a). In an effort to arrive
at a better appreciation of how extensive fl avonoid pigment variation is in the genus,
the most widely ranging species, L. californica DC. ex Lindley [= L. chrysostoma
(Fisch. and Mey.) Greene, in the earlier literature] was subjected to a more detailed
examination. Lasthenia californica is not only geographically the most widely distributed
taxon in the genus, but it is also known to occur on a variety of substrates,
which suggested that this system might provide some insight into how the species
responds to different edaphic situations. The site chosen for detailed study was
the Jasper Ridge Biological Preserve of Stanford University (referred to simply as
Jasper Ridge below), which lies south of San Francisco in San Mateo County in
the Santa Cruz Mountains (ca. 37°25′N, 122°2.5′W). One of the features of Jasper
Ridge is the presence of a serpentine outcrop that harbors an extensive population
of L. californica. Initial sampling was done along a transect approximately 1 km in
length running along the spine of the serpentine ridge. In addition to the anthochlors
that characterize this species, which were observed in all individuals, differences
in the nonanthochlor fl avonoid profi les were observed. Race A was distinguished
by the presence of fl avonol diglycoside sulfates and the fl avanone eriodictyol
7-O- glucoside (eriodictyol is the fl avanone equivalent to luteolin), whereas race C
exhibited only the basic array of anthochlor pigments. A third variant, called race
B in earlier papers, was observed in a few plants but is now included within race
C. Race B is characterized by the presence of luteolin 7-O-glucoside, in addition to
the basic array of anthochlors. Plants were also collected along several other transects,
each between 50 m and 65 m long, that lie at right angles to the ridge. Since
no additional pigment variants were observed in these shorter transects, no further
collections were made along the original long transect. We focus our attention, at
least for the moment, on a single transect.
Individual plants were collected at meter intervals, starting at a fi re-access road
near the crest of the ridge progressing downslope for a distance of 65 m. Elevation
change over this distance is approximately 5 m, which defi nes the drainage pattern
on this part of Jasper Ridge. Analysis of the individual plants showed that race C
plants occurred in the range 0–45 m after which only race A plants were observed
(Fig. 2.55). This pattern was closely approximated in plants collected along other
parallel transects on either side of the main transect. The site was visited each year
for a period of 6 years during which the distribution pattern of race A and race C
plants remained essentially unchanged (a race B plant was observed in the upper
portion of the transect during one season). These observations have been described
in a paper (Bohm et al., 1989) where it was pointed out that this was, at least to the
best of the authors’ knowledge, the only report of a fl avonoid distribution pattern
remaining constant over a period of years. Subsequent collections along the same
transect have shown the pattern to have remained constant for a period of 15 years
(N. Rajakaruna & B. A. Bohm, unpublished observations). Greenhouse studies