The Geography of Phytochemical Races

2.7 North and Central America 79
Fig. 2.49 Map of Notholaena standleyi sites, showing gold-race, yellow–green-race, and yellowrace
populations
from sites in southeastern Arizona, New Mexico, extreme southeastern Colorado,
Oklahoma, Texas, and north-central Mexico. This color form also occurs on igneous
rock, but can also be found growing on sandstone. The yellow–green race is known
from north-central Mexico and adjacent Texas and occurs on limestone (Fig. 2.49).
Despite the diffi culty of distinguishing the three color forms by means of clear-cut
morphological traits (yellow and yellow–green plants tend to be larger on the average
than gold-colored plants), their fl avonoid pigment profi les allow straightforward
separation. Seigler and Wollenweber (1983) examined the exudate chemistry of 59
specimens representing the entire range of the species. Qualitative and quantitative
differences were observed among color forms and little variation was observed within
populations. No intermediate fl avonoid profi les were noted. Pigment profi les were
based upon the existence of various combinations of O-methyl ethers of kaempferol
and herbacetin (8-hydroxykaempferol). The most obvious difference is the absence of
herbacetin derivatives from yellow race plants. Herbacetin 7-methyl ether [178] and
7,4′-dimethyl ether [179] were observed consistently but in smaller amounts in gold
race plants and both compounds were seen scattered in yellow–green race plants.
Yellow race plants exhibited kaempferol [180], kaempferol 3-methyl ether [181], and
kaempferol 4′-methyl ether [182] as major components. Kaempferol 3-methyl ether
was not seen in gold race plants and was observed only sporadically in yellow–green
plants. Structures are given in Fig. 2.50. Table 2.16 summarizes the occurrence data.
There are two obvious differences in pigment occurrence in this taxon. The fi rst
is the absence of herbacetin derivatives in the yellow race, which suggests the
apparent absence of an enzyme capable of placing oxygen at the C-8 position of the