The Geography of Phytochemical Races

76 2 Examples Within Continents
2.6.6 Tagetes minuta (Asteraceae)
Specimens of Tagetes minuta L. collected from three widely separated locations in
Argentina (Fig. 2.46) exhibited identical arrays of polyacetylene derivatives in their
roots, but had signifi cantly different relative amounts of these compounds (Gil et al.,
2002). Specimens were collected on the east coast near Buenos Aires (Pergamino at
33°56′S, 60°33′W), in the west near Mendoza (La Consulta at 33°44′S, 69°07′W),
and in the north near Salta (Cerrillos at 24°54′S, 65°29′W). The major compounds
were α-terthienyl (α-T) [171], 5-(3-buten-1-ynyl)-2,2′-bithienyl (BBT) [172] (see
Fig. 2.47 for structures), and BBTOH, an hydroxyl derivative of BBT. The Mendoza
and Salta populations exhibited low α-T and BBT concentrations and proportionately
higher levels of the BBTOH derivative. It is interesting to note that only in
the case of the material from Mendoza was there a positive relationship between
total thiophenes in the roots and total aboveground biomass. How signifi cant this
relationship would likely be over a longer period of time might be open to question,
considering that plants at this site exhibited the largest differences between years.
Large quantitative differences in otherwise identical qualitative profi les might
suggest that some sort of control system may be at work, but local environmental
conditions would have to be ruled out fi rst.
2.6.7 Hymenaea (Fabaceae)
The legume genus Hymenaea (including Trachylobium) comprises 16 species, all
but one of which occurs in the New World (Mabberley, 1997, p. 354). The exceptional
species, H. verrucosa Gaertner, which was formerly considered to constitute
the genus Trachylobium, is native to coastal East Africa including the eastern coast
of Madagascar. The East African species is the source of Madagascar copal. Among
the New World species, H. courbaril L., known locally as West Indies locust,
Brazilian copal, or anami gum (Mabberley, 1997, p. 354), is an important source of
resins used for the manufacture of varnishes. The species occurs in Mexico, Central
America, including Caribbean Islands, and in South America as far as southern
Brazil, which approximates the range of the genus in the New World.
Martin et al. (1974) collected specimens from 22 locations throughout the range
of H. courbaril and identifi ed a number of sesquiterpenes including caryophyllene
[173], humulene [174], selinene isomers [175 is β-selinene], and other related compounds
(see Fig. 2.48 for compounds 173–175). Caryophyllene and two selinene
Fig. 2.47 Compounds
171 and 172, thiophene
derivatives from Tagetes
minuta