The Geography of Phytochemical Races

128 3 After the Ice
Specimens from 29 populations, representing the entire range of the species, were
analyzed and found to exhibit extremely similar profi les (Soltis and Bohm, 1986).
Kaempferol [256], quercetin [253], isorhamnetin [257], and myricetin [258] 3-Omono-
and 3-O-diglycosides were observed in all specimens with variation limited to
3-O-triglycosides (see Fig. 3.1 for structures 256–258). Since the triglycosides were
present in much smaller amounts than the other glycoside classes and limited amounts
of plant material were used in the analyses, it was not possible to say with certainty
that triglycosides were absent (visual inspection of two-dimensional thin-layer chromatograms).
With that caveat in mind, it was concluded that there is no distinction
between the cytotypes based upon fl avonoid profi le, which is what one would anticipate
in an autotetraploid system.
3.1.3 Arnica (Asteraceae), a Note on Sedum (Crassulaceae),
and a Comment on Antennaria (Asteraceae)
The fi rst species of Arnica that we examine belong to subgenus Austromontana
Maguire, a North American group that consists of nine species (Maquire, 1943).
Members of the group occur over a large area in western North America, although
some of its constituent species have very limited ranges. Arnica cordifolia Hook.
and its derivative species A. latifolia Bong. are considered ancestral and occupy the
widest ranges within the subgenus. The fi rst detailed study of the fl avonoids of the
group focused on A. cordifolia, an apomictic polyploid complex that extends from
the Yukon Territory to central California and northern New Mexico, with disjunct
populations in Ontario and Michigan. Wolf and Denford (1983) sampled 33 populations
representing all fi ve known chromosome races with numbers ranging from
2n = 38 (diploids) to 2n = 114 hexaploids). Tetraploids are widespread and triploids
occur along the front ranges of the Rocky Mountains, while diploids, pentaploids,
and hexaploids are rare and are widely scattered. There was no correlation of fl avonoid
profi le with chromosome number, reminiscent of the fi ndings of Glennie et
al. (1971) on the Senecio radicans complex in Africa and adjacent regions where
eight chromosome races were involved. Similarly, diploid and tetraploid races of
Lasthenia californica (Asteraceae) show no relationship with fl avonoid profi les
throughout the range of the species (Desrochers and Bohm, 1993).
Quercetin 3-O-gentiobioside and quercetin 3-O-diglucoside [233-O-Glycs) were,
with a single exception, ubiquitous in the 33 populations of A. cordifolia. Apigenin
7-methyl ether (genkwanin) [259] (see Fig. 3.1 for structures 259–263) was seen in the
one population collected in California, and quercetin 3-methyl ether [260] was seen in
two populations, one in British Columbia and one in Oregon. 6-Methoxyapigenin (hispidulin)
[261], 6-methoxykaempferol 3-O-glucoside [262], and the 3-O-glucosides
of kaempferol and quercetin were all more or less randomly distributed throughout
the populations. Two compounds, however, showed regionalism in their distribution,
luteolin 7-O-glucoside [254] and 6-methoxyluteolin 7-O-glucoside [263]. Luteolin