The Geography of Phytochemical Races

14 2 Examples Within Continents
(4) a group consisting of limonene and α-pinene as codominant constituents. The
northern-most region was dominated by a race, represented by six sites, in which
citronellal was the major component, with concentrations ranging from 36.98% to
62.24% (Ave. = 48.32%). No other site yielded oil with higher than 25.63% citronellal.
The southernmost race (six sites) had limonene as the dominant terpene, with
concentrations falling in the range 43.18–56.92% (Ave. = 49.91%). The highest concentration
of limonene observed otherwise was 42.98% in one of the codominant
races. Populations in the middle of the range of this species tended to exhibit mixed
terpene compositions. The workers concluded that the citronellal race should best
be considered as an ecotype that has only recently evolved, a view supported in
fl oral bud and leaf morphology.
2.2.2 Duboisia myoporoides (Solanaceae)
The genus Duboisia consists of three species limited in occurrence to eastern Australia
(Fig. 2.6) and parts of New Guinea. Duboisia myoporoides R. Br., the taxon of interest
to us in the present context, is solely Australian in its occurrence. Evidence for the
existence of chemical variation within the species was fi rst described by Loftus Hills
et al. (1953, 1954) who observed that scopolamine [26] (see Fig. 2.7 for structures
26–30) was the dominant alkaloid in plants collected north of Gosford, New South
Wales, whereas hyoscyamine [27] was the dominant alkaloid in collections south of
Gosford. (Gosford, NSW, lies roughly between Newcastle and Sydney at 33°25′S,
151°18′E.) Later, a third variant was discovered in a region known as the Acacia
Plateau, near Killarney, Queensland (southwest of Brisbane), that was characterized
by the possession of the pyridine-based alkaloids, nicotine [28] and anabasine [29]
(see also Mortimer and Wilkinson, 1957). Other minor components reported, according
to Gritsanapan and Griffi n (1991), included valeroidine, valtropine, tigloidine,
tropine, butropine, norscopoline, poroidine, isoporoidine, acetyltropine, aposcopolamine,
noratropine, atropine, and tetramethylputrescine. None of these appears to
fi gure signifi cantly in the geographic patterning.
The most recent work, by Gritsanapan and Griffi n (1991), extended the range of
study to more northerly sites in Queensland and included populations at different
elevations. Four sites were studied: (1) northern Queensland at elevation 1000 m;
(2) near Tinaroo Dam on the Atherton Plateau (near Cairns, Qld.) at 2200 m;
(3) Mt. Glorious (near Brisbane) at 700 m; and (4) a revisited site at Acacia Plateau
at an elevation of about 1000 m. Scopolamine was the major alkaloid present in
plant material from Tinaroo Dam, from Mt. Glorious, and from coastal northern
Queensland. Accompanying scopolamine in the Mt. Glorious plants were nicotine
and anabasine. Plants from Acacia Plateau yielded a small amount of scopolamine,
which was the only tropane alkaloid detected, but major quantities of nicotine,
anabasine, and hygrine [30]. Hygrine was also observed as a lesser component of
plant material from the Mt. Glorious site. It is instructive to recognize that hygrine,
or a biologically active form thereof, lies on the biosynthetic pathway leading to the