The Geography of Phytochemical Races

5.2 Nonvascular Plants 241
that occurs in members of the genus. The fi rst example features L. obtusa (Huds.)
Lamour., a taxon known from the western Pacifi c, Indian, and Atlantic Oceans,
and the Mediterranean Sea. Caccamese et al. (1981) studied lipid-soluble components
of L. obtusa collected from four sites on the eastern coast of Sicily spanning
a distance of about 75 km from Castelluccio and Brucoli (the latter at 37°17′N,
15°11′E), south to Capo Murro di Porco (just south of Siracusa) and further to
Portopalo on the southeastern tip of the island (Fig. 5.13). The profi les of lipidsoluble
compounds from the four collections, as determined by GC-MS, were very
different, although some of the lesser compounds appeared to be shared between
some sites. The sample from Castelluccio, however, exhibited a compound, identifi
ed as laurencienyne [493], not seen in plants from the other three sites. It was
accompanied by a compound judged, on the basis of its identical mass spectrum,
to be the Z-isomer. A second compound from the Castelluccio site was identifi
ed as obtusenyne [494]. Plants from Brucoli afforded compound [495], known as
obtusadiol, as the major component. Plants from the most southerly site, Portopalo,
also afforded obtusenyne, and probably its E-isomer, but there was no evidence for
laurencienyne [493]. The major compound from plants from Capo Murro di Porco
was identifi ed as obtusin [496] (See Fig. 5.12 for structures 493–496). Among
the other compounds identifi ed from all sites were n-heptadecane and cholesterol.
Additional information on sesquiterpenoids from L. obtusa can be found in Amico
et al. (1991).
Those authors also demonstrated that neither sexual stage nor age of plant had
any effect on the qualitative composition of the lipid fractions. They did comment,
however, on the possibility that the secondary chemical output of plants at these
different sites might refl ect local environmental conditions, especially considering
that the distance between the sites at Castelluccio and Brucoli is only a few kilometers.
They pointed to the work of Howard et al. (1980), who had demonstrated
such effects on the chemical content of two species of Laurencia in California over
Fig. 5.13 Map of eastern Sicily showing Laurencia obtusa collection sites