The Geography of Phytochemical Races

2.3 Europe 33
Fig. 2.17 Biosynthesis of fl avone glycosides in Silene with glycosylation genes identifi ed
Whereas g X and gl A are rare in S. latifolia, there is a clear-cut geographic patterning
of the other genes. In one of the earlier studies, van Nigtevecht and van
Brederode (1972) mapped the frequency of g, g G , gl, and gl R in 54 populations.
The initial mapping resulted in the recognition of two races in Europe, an eastern
one consisting of a high frequency of isovitexin 2″-O-rhamnoside along with isovitexin,
and a western one consisting of isovitexin 7-O-glucoside and isovitexin. In an
extension of this study, Mastenbroek et al. (1982) examined 285 populations, allowing
a more detailed mapping of fl avonoid variation patterns. Three pigment races
became apparent. The fi rst of these, which occurs in western and southern Europe
and has g G , gl, and fg present at a frequency of 1.0, is equivalent to the Western race
observed in the fi rst survey. Referring to the table, we see that this arrangement is
manifested in a pigment profi le consisting of isovitexin and its 2″-O-rhamnoside.
The second race, which occurs in central Europe reaching northward into southern
Norway, is characterized by a high frequency of g and gl R , and a low to intermediate
frequency of Fg. This translates into a pigment profi le dominated by isovitexin
and its 2″-O-rhamnoside with isovitexin 2″-O-glucoside present in some populations.
The third race occurs in eastern Europe and consists of high frequencies
of g G , gl R , and fg, which yields a pigment profi le consisting of isovitexin, and its
2″-O-rhamnoside and 2″-O-glucoside.
The next step in fi ne tuning the distribution map involved collection of specimens
from areas not well represented in the earlier studies, and included areas where the
fl avonoid races came into contact (Mastenbroek et al., 1983a; Mastenbroek and van
Brederode, 1986). A further set of populations, bringing the total to 358, provided
even better resolution and established the existence of transition zones between
adjacent chemical races (see appendix in Mastenbroek, 1983). Analysis of the larger
data set, using principal-components analysis and cluster analysis, established the
existence of eight zones, the main western European race (Scotland to Spain and to
the Balkans), the second main race (Central Europe: Hungary, Czechoslovakia, and
Germany), the third main race (Russia, Poland, and Finland), and fi ve intermediate