The Geography of Phytochemical Races

4.4 South Pacifi c 209
Fig. 4.15 Compounds 365–371, fl avonoids from Nothofagus
5-hydroxy-7,8-dimethoxyfl avone [367], the fl avanone pinocembrin [368], the
dihydrofl avonol pinobanksin [369], 2′,4′-dihydroxy-6′-methoxychalcone [370],
and the stilbene pinosylvin [371].
There is a remarkable homogeneity of pigment occurrence among the four taxa,
the major difference being the restriction of 5-hydroxy-7,8-dimethoxyfl avone to
the New Zealand species, N. solandri. This species is also distinguishable from the
others by a more complex mixture of 8-hydroxygalangin methyl ethers. The key
observation here is the virtual identify of profi les of the Chilean species with the
profi le exhibited by the New Zealand species suggesting that essentially no divergence
in fl avonoid biosynthetic capacities has occurred during the time these taxa
have been separated from their common (?) ancestor. As just noted, the fl avonoid
profi le of N. solandri is somewhat more complex than those of the other species, but
only by degree and not by major shifts in biosynthetic activities. On the other hand,
N. gunnii, the Tasmanian representative, was found to exhibit the simplest pigment
profi le, with about half the number of galangin derivatives seen in the other taxa.
The data are presented in Table 4.6. It is diffi cult to assess the signifi cance of data
such as these, especially in the face of the powerful genetic tools used by Manos
and others in this, and other, work. As commented in other places in this review,
an examination of the comparative enzymology, and/or sequence divergence of the
genes encoding the enzymes responsible for producing these compounds could be
very useful. For example, if a time of divergence for the Chilean and New Zealand
members of subgen. Fuscospora could be estimated from the DNA data, it might
indicate the time period during which the fl avonoid pathway enzymes had not
diverged appreciably, as appears to be the case with N. alessandri and N. fusco, but
have diverged, as in the case of N. gunnii and N. solandri. The O-methyltransferase
system seems a likely candidate for such comparative studies.