The Geography of Phytochemical Races

70 2 Examples Within Continents
2.6.2 Cunila galioides (Lamiaceae)
According to a recent paper by Echeverrigaray et al. (2003), the genus Cunila
consists of 22 species with two centers of diversity, Mexico with 10 species, and
southern South America with the remaining 12. Cunila galioides plants were
collected from 20 sites, 15 in Rio Grande do Sul State and fi ve in Santa Catarina
State, and subjected to analysis of their essential oils. Of the 40 compounds identifi
ed, 14 were present in levels above 10% (of the total oil yield) and were used for
statistical analysis. Three chemotypes emerged from the analysis: group 1 (the citral
group, C 10 acyclic aldehyde); group 2 (the ocimene group, C 10 acyclic alkene); and
group 3 (the menthene group, C 10 cyclic derivatives). [Note: each group consisted
primarily of compounds related to the group type.] Geographic differentiation was
clearly indicated by the various treatments with group 1 occurring in the northeast
plateau of Rio Grande do Sul, group 2 occurring in grasslands at higher elevations,
and group 3 occurring in the transitional area between the other two. Mean annual
temperature, rainfall, and soil type differed between the two principal groups.
That the chemical profi les were under genetic rather than environmental control
was determined by micropropagation and fi eld growth. In all cases, plants grown
under controlled conditions exhibited chemical profi les identical to those of plants
collected from nature. The authors concluded that chemical differences among the
populations was caused by localized inbreeding, low level of recessive gene expression,
and selection of particular chemical types in response to differing herbivore
pressure in the different environments.
2.6.3 Cinchona (Rubiaceae)
One of the major diseases of humankind has been and continues to be malaria. The
most effective agent used to battle malaria entered Western medicine, ironically,
through the agency of the Spanish conquest of South America. One of the features
of some of the native peoples of South America was a sophisticated pharmacopoeia
that included the bark of a tree from Peru used to combat fever. The bark of the
“fever tree,” as the early explorers named it, appeared in Europe in the fi rst half of
the seventeenth century (Agosta, 1996). The plant was brought to the attention of
Linnaeus who provided the generic name by which it remains known, Cinchona.
[Agosta (1996) tells the story of how this particular name, actually misspelled, came
to be chosen by Linnaeus!] Eventually, studies of the active principles of the plant
resulted in the discovery of quinine [166] and a number of related compounds,
such as quinidine [167], cinchonine [168], and cinchonidine [169] (see Fig. 2.43 for
structures 166–169). Cinchona, with some 40 species, is a moderately large genus
of shrubs and trees in Rubiaceae, most of which occur in the Andes but which is
also represented as far north as Costa Rica (Mabberley, 1997, p. 158). The interested
reader might wish to consult Steere (1945a, b) and Rainey (1946), as well as the
recent description by Agosta (1996), for additional background information.