The Geography of Phytochemical Races

168 3 After the Ice
Fig. 3.12 Map of Fitzroya
cupressoides occurrence
β-acoradiene [295]. These compounds were seen in all other trees but apparently at
signifi cantly different quantitative levels. For structures 286–298 see Fig. 3.13.
The second chemotype (their Type 1) had, in addition to the Type 0 array, substantial
amounts of α-longipinene [297] and an unidentifi ed sesquiterpene alcohol. The
third chemotype (their Type 2) was distinguished by the presence of, among other
compounds, cedrene isomers, [α-cedrene is shown as 298], and large amounts of the
isomeric sesquiterpene alcohols α-acorenol [294] and its β-isomer [295]. The acoradiene
isomers [295 and 296] were also identifi ed. Some geographic patterning was
observed in the Type 0 chemotype when the data were subjected to numerical analysis:
a trend in the reduction of caryophyllene content was revealed in a west to east direction.
The data sets for Types 1 and 2 were too small to allow for similar analysis.
The second study, which addressed glacial history directly, involved an analysis
of isozymes and how patterns of variation could be used to test whether there
had been a single refugium or whether there had been two, or possibly more, refugia
(Premoli et al., 2000). Geomorphological and palynological evidence revealed
that a refugium existed from northwestern Chiloé Island (ca. 40° S) and along the
coast on the Chilean mainland to about 40° S latitude (Heusser and Flint, 1977; see
also Vuilleumier, 1971). If this had been the sole refugium (their Single Refugium
hypothesis), then one would predict that genetic variation of trees along the eastern
slopes of the Andes would be lower than that of trees in the refugial population.
The situation becomes somewhat more complicated if one considers the effects
on genetic variation if more than one refugium had existed. Premoli et al. (2000)
discussed two effects: the Cordillera effect and the extent-of-the-ice effect. In the
case of the Cordillera effect, the assumption was made that there was incomplete ice
coverage, resulting in patches of forest remaining intact on either side of the Andes;
this amounts to the existence of multiple local refugia that would supply propagules