The Geography of Phytochemical Races

222 5 Wide Disjunctions
Fig. 5.3 Compounds 395–405, lichen acids from species of Pseudevernia, Rhizoplaca, and
Thamnolia
that plant material collected in Chile afforded (−)-usnic acid [398] as, presumably,
the sole component (Huneck and Follmann, 1964). Soon thereafter, a specimen
from the Alps was shown by Eigler and Poelt (1965) to accumulate both
(−)-usnic acid and psoromic acid [399], compounds that have also been reported
from Canadian accessions (Huneck et al., 1968; Thompson et al., 1969). A more
recent contribution to the list of chemical races also involves material collected
in Chile. Thus, Piovano et al. (1997) not only reported both usnic and psoramic
acids, in agreement with the earlier results but also identifi ed protolichesterinic
acid [400], which they suggested might be the unidentifi ed compound mentioned
by Follmann and Huneck (1972), plus two compounds hitherto not reported from
this species, namely, ergosterol peroxide [401] and physodalic acid [402]. Those
workers suggested that these differences might refl ect the organism’s response to