The Geography of Phytochemical Races

4.3 North Pacifi c 193
is interesting insofar as the two sets of taxa are thought to have been isolated
since the Bering land bridge became submerged, possibly as long ago as 12 mya
(Sanders, 1979).
A more recent electrophoretic analysis of 40 populations representing all eight
species provided meaningful information on 11 enzyme systems (Vogelmann and
Gastony, 1987). The Asian species differs from the North American species at only
two of the 15 loci examined, which also represents a comparatively small level of
differentiation for taxa separated by this length of time. This apparent close relationship
is not supported by crossing studies (Vogelmann, 1985), which demonstrated
that artifi cial interspecifi c crosses yielded only sterile offspring.
4.3.3 Cladothamneae (Ericaceae)
Tribe Cladothamneae of Ericaceae (subfam. Rhododendroideae) consists of
four species that have at one time or another been placed variously in four genera:
Botryostege Stapf, Cladothamnus Bong., Elliottia Muhlenb. Ex Elliott, and
Tripetaleia Siebold & Zucc. For the purposes of the fl avonoid study (Bohm et al.,
1978), the nomenclature of Copeland (1943) was used, wherein Cladothamnus was
taken to consist of the single species C. pyrolifl orus, the western North American
member of the group, and three species of Tripetaleia, T. bracteata, and T. paniculata
from Japan, and T. (Elliottia) racemosa from Georgia and adjacent South Carolina.
[Note that the fi nal suggestion by S. Brim and P. F. Stevens (co-authors of the
Bohm et al. 1978 work) was that similarities suggested that the four species are best
recognized as belonging to a single genus, Elliottia.] The taxonomy of the subfamilies
and tribes of Ericaceae has been reviewed by P. F. Stevens (1971).
The fl avonoid profi les of all four species are based upon the common fl avonols,
such as kaempferol, quercetin, isorhamnetin, and myricetin. Kaempferol and quercetin
derivatives are the most common constituents, myricetin derivatives much
less so, while isorhametin was seen only in T. paniculata. Although the aglycone
chemistry of the tribe is comparatively simple, the glycoside profi les of the four
species exhibit several interesting differences. The most common glycosides are,
as one might expect, 3-O-mono- and 3-O-diglycosides, with the usual sugars being
present, such as arabinose, glucose, galactose, glucuronic acid, and rhamnose,
although not all taxa contain the same sugars. Nor do all taxa exhibit the same
degree of glycosylation, wherein lie the main distinguishing features within the
tribe. Kaempferol and quercetin 3-O-rutinosides are among the major components
of Elliottia species, whereas they were not seen in Cladothamnus (Bohm and Saleh,
1972; Bohm et al., 1978). Tripetaleia (E.) paniculata is unique within the group
in accumulating quercetin 3-O-arabinosylrhamnoside. Cladothamnus, in contrast,
accumulates kaempferol and quercetin 3-O-galactoside-7-O-rhamnosides and
3-O-arabinoside-7-O-rhamnosides. Quercetin 7-O-rhamnoside was also detected
in extracts of C. pyrolifl orus. This compound might have been an intermediate in
the formation of the 3,7-diglycosides, although it would seem more likely that the