The Geography of Phytochemical Races

4.2 Across the Indian Ocean (Primarily) 187
or anatomical features. In a broad sense, it would be possible to infer how often a
particular compound or compound type has appeared or disappeared within the evolutionary
history of the taxon. Our current level of understanding of the enzymes
and genetic control of the fl avonoid pathway, for example, would provide valuable
insights into which gene or genes might be involved in the processes, specifi cally,
which might be likely points of control of the pathway. In the case of Restionaceae,
a generic phylogeny would provide an opportunity to judge the relative level of
advancement of O-methylation, and thereby provide a possibly defi nitive answer to
the question of whether the appearance of isorhamnetin in Australian genera represents
a gain or a loss. Observations of that sort would not only advance our understanding
of the evolution of a particular character within the family, but would also
almost certainly provide a better view of a major fl avonoid biosynthetic process.
The same argument could be made about the enzyme(s) responsible for the formation
of the 8-hydroxylated fl avone hypolaetin, which was observed exclusively in
Australian members of the family.
A well-resolved species phylogeny could also provide useful information on
evolution of fl avonoid structural features unique to one or a group of species. Linder
and Mann (1998) have described such a study for 37 species in the restionaceous
genus Thamnochortus. What is needed is a detailed chemical analysis of this genus
to see if any chemical patterns exist that parallel patterns based on the morphological
data. Their observation that a strong relationship exists between species
occurrence and rainfall would provide an opportunity to examine the infl uence of
drought on the formation of cuticular components such as long-chain hydrocarbon
derivatives or nonpolar fl avonoids.
4.2.3 Villarsia (Menyanthaceae)
Another example of an Australian–South African disjunction involves members of
Villarsia, one of the fi ve genera that comprise Menyanthaceae. The family, although
comparatively small, offers a number of interesting distributional problems. Three
of the genera are monotypic, Menyanthes (M. trifoliata L.) is circumboreal;
Faurea cristi-galli (Menzies ex Hook.) Mak. occurs in eastern Asia and western
North America; while Liparophyllum gunnii J. D. Hooker is known from Tasmania
and New Zealand. The largest genus, Nymphoides, consists of about 35 species and
is nearly cosmopolitan. The genus of interest here, Villarsia, consists of one species
in the Cape Province of South Africa, V. capensis (Houtt.) Merrill, one species in
Southeastern Asia, and perhaps a dozen in Australia.
An examination of the fl avonoids of Villarsia (Bohm et al., 1986) revealed a
heterogeneous array of fl avonol glycosides, based upon kaempferol, quercetin,
and isorhamnetin, with each species exhibiting a unique assortment. Surprisingly,
there were greater similarities between the pigment profi le of V. capensis and species
from eastern Australia, V. exaltata (Soland. ex Sims) G. Don from Tasmania
and V. reniformis R. Br. from New South Wales, than with species native to