The Geography of Phytochemical Races

6.9 Macaronesia 281
126 individuals were analyzed by HPLC revealing six caffeic-acid derivatives, fi ve
luteolin mono-C-glycosides, two luteolin di-C-glycosides, a tricin O-glycoside, and
a mixture of luteolin mono-C-glycosides and apigenin di-C-glycosides. Principalcomponents
analysis (PCA) revealed seven identifi able groups reckoned by their
centroids: (1) coastal populations from Madeira representing subsp. marina, but
differing in phenolic pattern from coastal Portuguese specimens of subsp. marina
(Borrill) W. Greuter; (2) tetraploids from Madeira identifi ed as subsp. hylodes;
(Parker) J. Holub; (3) diploids from Tenerife identifi ed as subsp. smithii (D. smithii
Link?); (4) tetraploids from the center of La Palma; (5) tetraploids from the center
of Grand Canary; and (6) and (7) populations from the coast of Portugal identifi ed
as subsp. marina. Clearly separated from all other groups was the population from
Grand Canary. Individuals from this population exhibited a unique combination
of phenolic compounds. Individuals from this population also exhibited specifi c
alleles at several loci (Sahuquillo and Lumaret, 1995), as well as morphological
features resembling both subtropical and Mediterranean members of Dactylis.
Populations from this area are also ecologically different, in that they grow at
high elevations in dry habitats not infl uenced by the ocean to the degree experienced
by other groups. As Jay and Lumaret (1995) pointed out, this combination of features
suggests that these Grand Canary populations are likely to have been isolated
for a long time. Although the other PCA-group centroids were separated from one
another, the level of individual variation resulted in signifi cant overlap. A second
PCA of tetraploid individuals from ten geographic locations again resulted in clear
separation of the Grand Canary plants, but with even greater overlap among the
other populations. Included in this analysis were representatives from the French
Alps (subsp. reichenbachii, nomenclature?) and from the south of France (subsp.
hispanica; D. hispanica Noe ex Steud.?). These groups were clearly distinguished
from both of the others, although there was a good deal of overlap among them.
In their concluding remarks, the authors pointed out the contrasting infl uences
experienced by Dactylis on these islands, ranging from genetic differentiation in
isolation, as in the Grand Canary situation, to possible adaptive value of different
combinations of phenolic compounds, as seen in the heterogeneous populations on
Madeira.
A recent examination of chloroplast DNA variation has provided additional
insights into the evolutionary history of cock’s foot (Sahuquillo and Lumaret,
1999). Plant material was collected from six diploid and 15 tetraploid populations
(121 individuals in all) representing the Canary Islands, Madeira, the coasts of Portugal
and Spain, and sites in Morocco (northern and northwestern Africa). Eight
restriction enzymes yielded fragments that defi ned two “chlorotypes,” chlorotype I,
considered to represent the ancestral type, and chlorotype II characterized by a 290base-pair
deletion. Chlorotype I was found to be the predominant form, occurring
in the majority of continental populations and in the westernmost Macaronesian
islands. It was found in both diploids from Tenerife, one from the lowland scrub and
the other from the high-elevation heath. It also characterized the tetraploids endemic
on Madeira and La Palma. Chlorotype II occurred in populations from the eastern
end of the archipelago, that is, the islands nearest Africa, and in a few diploid and