The Geography of Phytochemical Races

2.7 North and Central America 93
2.7.6 Brickellia cylindracea (Asteraceae)
From the southern part of the United States comes an example where fl avonoid
profi les from disjunct populations indicate a closer relationship than might otherwise
have been recognized. Brickellia cylindracea Gray & Englem. occurs over an
area including southern Texas and displays a level of morphological variation that
suggested to at least one worker that a population in the Big Bend area of western
Texas (Fig. 2.57) might be suffi ciently different from populations in central Texas
to warrant its recognition as a formal taxon (A. M. Powell, personal communication
to Timmermann and Mabry, 1983). As part of a large-scale study of fl avonoids of
Brickellia, Timmermann and Mabry (1983) investigated the pigments in collections
from both areas. Identical arrays of fl avonols, including both aglycones and glycosidic
forms, were observed for each. The compounds identifi ed were derivatives of
quercetagetin, including the 3,6,4′-trimethyl [190], 3,6,3′,4′-tetramethyl-[191], and
3,6,7,3′,4′-pentamethyl ethers [192] (Fig. 2.58). These data were taken as evidence
Fig. 2.57 Map showing sites
for Brickellia cylindrica (Bc)
and Helianthus maximiliani
(Hm) studies
Fig. 2.58 Compounds 190–192, fl avonoids from Brickellia cylindrica