The Geography of Phytochemical Races

280 6 Oceanic Islands
Fuerteventura, and Lanzarote. The islands are volcanic and range in age from less
than 1 million to about 21 million years (Carracedo, 1994). Two recent papers
present detailed accounts of the geologic history of the Canary Islands along with
extensive literature reviews (Anguita and Hernan, 2000; Dañobeitia and Canales,
2000). The Cape Verde archipelago consists of several small islands centered at
16°00′ N, 24°00′ W, to the west of Senegal. The Madeira archipelago consists of
two main islands, Madeira (32°45′N, 17°W) and the much smaller Porto Santo
(33°04′N, 16°20′W). The Selvagens Islands, among the smallest of the Macaronesian
group, consist of two small landmasses at ca. 30°00′N, 16°00′W, which puts
them roughly one-third of the way between the Canary Islands and the island of
Madeira.
6.9.1 Anomalographis madeirensis (Graphidaceae)
Differences in the depsidone chemistry of the lichen Anomalographis madeirensis
(Tav.) Kalb. have been noted by González et al. (1999), who reported identifi cation
of stictic (see Fig. 5.4 for structures), norstictic, and cryptostictic acids from a specimen
collected on Tenerife. In contrast, Kalb and Hafellner (1992) reported stictic
and norstictic acids from material of this species collected on Madeira, but did not
fi nd cryptostictic acid. They did fi nd two other depsidones, however, that is, constictic
and connorstictic acids. It would be interesting to know if plants from these
two sites respond to differences in localized microhabitats by synthesizing different
arrays of compounds similar to the case with Ramalina siliquosa in Wales, which
was commented upon above.
6.9.2 Dactylis glomerata (Poaceae)
Dactylis is a small genus thought by some to be monotypic, consisting only of
D. glomerata L. (cock’s-foot), a Eurasian native now widely naturalized in other
parts of the world. That the species is complex can be seen in the recognition of
15 diploid (2n = 14) members as subspecies (Stebbins and Zohary, 1959; Lumaret,
1988). In Macaronesia, several morphologically and chromosomally distinct entities
are restricted to single islands, and some islands support different subspecies
in different habitats. Dactylis has also been divided into three climatic groups,
mesic-temperate, Mediterranean, and subtropical (Lumaret, 1988), each of which
may have both diploid and tetraploid members.
In order to gain a better understanding of the relationships and evolutionary
history of Dactylis, Lumaret and colleagues have undertaken extensive studies of
various biochemical markers. The fi rst of these that can be examined is the fl avonoid
analysis of the Atlantic part of the subtropical group (Jay and Lumaret, 1995). In all,