The Geography of Phytochemical Races

6 2 Examples Within Continents
Fig. 2.2 Compounds 1–5 from Senecio radicans complex; Compounds 6–9 from Pearsonia
quercetin 3-methyl ether [3], apigenin 7-O-glucoside [4], and 6,8-di-C-rhamnosylapigenin
[5]. The fi rst point of interest is that fl avonoid profi les of individual taxa did
not correlate with ploidy level. Individuals with 2n values of 20, 30, 40, 60, 80, 100,
and 102 were included in the survey as well as S. angulatus L. f. that has 2n = 180.
The most striking profi le difference reported involved S. longifl orus Sch. Bip. var.
madagascariensis Rowl. from Madagascar, S. longifl orus var. violacea Berg. from
Kenya, and S. kleinia Sch. Bip. from the Canary Islands. The fl avonoid profi les of
these taxa consisted solely of quercetin 3-O-glucoside, a compound not otherwise
detected in the study. Quercetin 3-O-rutinoside, on the other hand, was observed in
all but a scant few other specimens. Kaempferol 3-O-glucoside and 3-O-rutinoside
were more scattered in their occurrence as was quercetin 3-methyl ether and the
fl avone derivatives. Senecio angulatus, with 2n = 180, was unique within the taxa in
having only apigenin 7-O-glucoside and 6,8-di-C-rhamnosylapigenin. Other geographic
correlations include the observation that apigenin 7-O-glucoside occurs uniformly
in taxa from South West Africa, but only sporadically in South African ones.
6,8-Di-C-rhamnosylapigenin, conversely, was not observed in taxa from South West
Africa but was present in most specimens from South Africa.
Perhaps the most unusual observation in this study, other than the unique pigment
profi le in S. angulatus, is the simple and identical fl avonoid profi le in the Kenyan,
Madagascaran, and Canary Islands specimens. A close relationship between the two
varieties from East Africa is not diffi cult to appreciate. The occurrence of this profi le
in specimens from the Canary Islands, however, points to a closer relationship than
the distance between these areas might suggest. There is no way to know, at least from
the data presented, whether this represents a case of convergence of fl avonoid biosynthetic
capacities involving unrelated species, whether it points to a relationship based