The Geography of Phytochemical Races

282 6 Oceanic Islands
tetraploid Mediterranean populations growing at higher elevations. Chlorotype II
was also observed in tetraploid populations from La Gomera (one of the western
islands) and in one of the seven populations examined from Madeira. These results
were taken to indicate that introgression from Mediterranean material into tropical
forms has happened, possibly several times, and that repeated colonization of
the islands from the mainland or between islands has likely played a major role in
development of the patterns of variation observed.
An earlier paper by Jay et al. (1984) should be consulted for information on patterns
of variation in D. glomerata representing populations from Scotland, southern
France, and the Mediterranean islands of Corsica and Sardinia. The fl avonoid profi
les, based on mono- and di-C-glycosylfl avones, were clearly sorted into three
geographical groups, but not strictly according to subspecifi c limits.
6.9.3 Laurus azorica (Lauraceae)
Laurus azorica (Seub.) Franco (=L. canariensis Webb & Berth.) is an endemic species
on the Azores, the Canary Islands, and Madeira, where it occurs as a component
of the laurel-juniper cloud forest community. The other member of the genus is the
so-called “true bay,” L. nobilis L. A recent study by Pedro et al. (2001) described
the essential-oil chemistry of L. azorica collected from ten populations representing
fi ve Azorean islands, Faial (3 populations), Pico (1), Sao Jorge (2), S. Miguel
(2), and Terceira (2). Monoterpenes dominated the foliar-oil fraction with α-pinene
(15–37%), β-pinene (9–18%), and 1,8-cineol (12–31%) as the major components.
Major monoterpenes of oil from unripe berries were α-pinene (12–22%), β-pinene
(7–13%), trans-β-ocimene (27–45%), and cis-β-ocimene (9–16%). Cluster analysis
revealed that two clear-cut groups exist based upon the enantiomeric composition
of the pinenes. The two populations from Sao Jorge were strongly differentiated
from all other populations. Analysis of plant material from the Santo António site
on Sao Jorge from different years revealed consistent results. Information on oil
composition of plants from the Canary Islands and Madeira would have been useful
in helping to assess the signifi cance of these interpopulational (and inter-island)
differences, in particular, are the populations on Sao Jorge more closely related to
populations from one of the other archipelagoes, or is the difference in chemistry
the result of a strictly local event or local conditions?
6.9.4 Todaroa aurea (Apiaceae)
Todaroa is a small genus endemic to the Canary Islands. According to González
et al. (1988), who were interested in secondary metabolites of the genus, T. aurea
Parl. was regarded “tentatively” as a single species endemic to the four westernmost
islands of the archipelago. Chemical analysis of specimens collected on two islands,