The Geography of Phytochemical Races

2.2 Australia and New Zealand 19
fl ooding), or some other genetic control mechanism over oil chemotypes.” Genetic
differentiation between the NSW and Queensland populations, using other techniques,
has also been revealed (Butcher et al., 1992; Aitken et al., 1998; Rossetto
et al., 1999). As in numerous other situations encountered in the literature, a population
phylogeny of M. alternifolia would likely provide valuable insights into the
evolutionary relationships within this species.
A detailed statistical analysis of chemical composition and morphological differences
of trees from 40 populations was recently described by L. S. Lee et al. (2002).
Three drainage catchments were represented, the Clarence and Richmond Rivers
in NSW and the Severn River in Queensland. The two NSW sites represent warm
and moist environments; the Severn site is higher and drier. The results of this set of
analyses pointed to the existence of signifi cant differences in chemotype representation
in the different catchments. Also, this is the fi rst report that there is a relationship
between chemotype and tree size, with the trees from the Queensland site being
the smaller. The higher level of chemotype differentiation in the Queensland population
lies in opposition to the lower level of genetic variation recorded for trees
from that area as pointed out above (Rossetto et al., 1999). Whether the differences
recorded in the recent paper are the result of genetic divergence or to environmental
differences has not been fi rmly established.
Melaleuca quinquenervis also ranges along the eastern coast of Australia from near
Sydney in New South Wales, north to the Cape York Peninsula, Queensland and along
the southern coast of Papua New Guinea and in New Caledonia. Ireland et al. (2002)
made extensive collections of leaves of this species for study of essential oil content.
Two clear-cut chemotypes emerged, one characterized by E-nerolidol (74–95%) and
linaloöl (14–30%), both acylic C-10 terpene alcohols, representing the “southern”
race, and one characterized by combinations of 1,8-cineole (10–75%), viridifl orol
(13–66%), α-terpineol (0.5–14%), and β-caryophyllene (0.5–28%) [98] comprising
the “northern” race. In addition to the compositional differences, oil yield differed signifi
cantly between the two areas with yields less than 0.5% from northern race plants
and yields of 1.5–3.0% in southern populations. The southern race extended from
Sydney northward to Selection Flat, NSW with a disjunct population farther north
near Maryborough in Queensland. It was possible to discern sub-races within the
southern chemotype based upon linaloöl concentration. The northern form occurred
throughout the range of the species, but was only rarely seen in the south. Variation of
the major components appeared to vary continuously. The authors offered no explanation
for the existence of several chemotypes within this species, but did note that the
time of year during which collection took place did not infl uence the results.
2.2.5 Isotachis lyallii (Balantiopsidaceae)
Isotachis lyallii Mitt. is a liverwort that occurs on both the north and south islands
of New Zealand. A study of the lipid fraction of this species collected from both
islands revealed different secondary metabolite profi les involving sesquiterpenes
and aromatic esters (Asakawa et al., 1997). The sesquiterpene array consisted of