The Geography of Phytochemical Races

236 5 Wide Disjunctions
obtained. Extensive studies of the genus have shown the existence of both more or
less local as well as very widespread patterns of variation. For example, König et al.
(1999) recorded variation in the existence of both cyclic and acyclic compounds
in P. harmatum J. Agardh collected from three areas on the Great Barrier Reef of
Australia. Specimens were collected from six sites representing northern, central,
and southern parts of the reef: Milne Reef and Telford Reef from the Cairns Section
(Cairns lies at 16°51′S, 145°43′E); Orpheus Island (18°40′S, 146°30′E), Rib Reef,
and Potter Reef from the Central Section; and Heron Island (23°25′S, 151°55′E)
from the Mackay/Capricorn Section (Fig. 5.10). This species proved to be a rich
source of compounds, whose structures appear in Fig. 5.11, marked [477–487].
The terpene profi le of plants from the three areas exhibited a good deal of variation,
ranging from the richest arrays seen in plants from the northern sites, through
highly heterogeneous arrays in plants from the central part of the range, to a comparatively
simple array in plants from the Heron Island site. Only in the case of
northern region were identical chemical profi les observed in plants from different
sites (Milne and Telford Reefs). The data appear in Table 5.3.
Tests of biological activity revealed that compound [480], whose complete structure
was determined to be (1S,2S,4R,5R,1′E)-2-bromo-1-bromomethyl-1,4-dichloro-
5-(2′-chloroethenyl)-5-methylcyclohexane by X-ray crystallographic analysis, is
very toxic to Chlorella fusca under laboratory conditions. The other compounds
Fig. 5.10 Map of the Great
Barrier Reef, Australia