The Geography of Phytochemical Races

58 2 Examples Within Continents
thymolic infl orescences, thymolic leaves, carvacrolic infl orescences, and carvacrolic
leaves, and that they can learn to select each of the identities separately.
2.4.6 Lavandula stoechas (Lamiaceae)
A study of Lavandula stoechas L. subsp. stoechas along an east–west transect in
Crete demonstrated that signifi cant variation in essential oil composition can exist
on an even smaller scale than those described above (Skoula et al., 1996). Four
wild populations were sampled over a distance of about 150 km: Fodele at 24°58′E,
Akrotiri at 24°07′E, Lakki at 23°57′E, and Sfi nari at 23°34′E (latitude was the same
throughout). The main compounds identifi ed, in order of decreasing abundance,
were fenchone [128], 1,8-cineole [41], camphor [93], and α-pinene [22]. For example,
fenchone concentrations ranged from 10.4% to 56.3% in infl orescence oils and
from 18.7 to 48.9% in leaf oil; α-pinene from 1.8% to 14.2% of infl orescence oil
and from 0.5 to 3.4% in leaf oil. α-Cadinol, which was only seen in the two centrally
located populations, reached a concentration of 9.2% in infl orescence oil and
7.7% in leaf oil. Discriminant function analysis showed that the Fodele population,
in which 1,8-cineole predominates with fenchone and camphor as lesser components,
is clearly distinguished from the other populations. The Fodele population
was thus recognized as constituting a second chemotype characterized by the 1,8cineole/fenchone
combination, as opposed to the other populations recognized as
the fenchone/camphor chemotype. The numerical analysis showed a great deal of
overlap among the three westernmost populations. The discovery of a chemotype
dominated by 1,8-cineole takes on added signifi cance when one appreciates that
L. stoechas subsp. stoechas populations sampled from Greece (Kokkalou, 1988),
Cypress (Valentini et al., 1993), Morocco (in Valentini et al., 1993), and Spain
(Garcia-Vallejo et al., 1990; Negueruela, 1990) all had fenchone as the predominant
essential oil component.
For additional studies of geographic (and seasonal) variation of essential oils in
other members of Lamiaceae, interested readers should consult a study of Thymus
caespitosus Brot. in Portugal (Salgueiro et al., 1997), Origanum vulgare L. subsp.
hirtum (Link) Letswaart in Greece (Vokou et al., 1993; Kokkini et al., 1994, 1997),
and Origanum X intercedens (a hybrid between O. onites L. and O. vulgare L.
subsp. hirtum (Link) Letswaart) (Kokkini and Vokou, 1993). The last mentioned
work involved a study of the hybrid on the Greek island of Nisyros and its resemblance
to O. vulgare subsp. from the neighboring island of Kos.
2.4.7 Mentha suaveolens (Lamiaceae)
This example involves a study of free fl avonoids (aglycones) present on the leaf
surface of Mentha suaveolens Ehrh. (Lamiaceae) growing in Spain and in Algeria