Volatile aromatic compounds in Mediterranean plant communities
(I) Physiology of
compound synthesis (II) Effects on competitors,
herbivores, and pollinators
(III) Adaptation
to water and nutrient stress (IV) Atmospheric
chemistry
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Mediterranean-climate regions can be found in five
distinct regions of the world: the Mediterranean Basin, Western
and South Australia, California, central Chile, and the Cape Region of
South Africa.
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Mediterranean-type climates are characterized by a highly uneven annual
distribution of rainfall (with 90% or more of annual precipitation falling
in the six cool season months), mild winter conditions with infrequent
and relatively mild frosts, and frequent periods of extended summer drought
(Rundel
1998).
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Although mediterranean-type ecosystems cover a tiny 1.2% of the earth’s
surface (Rundel 1998), they contain about
48250 plant species, or an astounding 20% of the world's total. In
terms of regional diversities of species these ecosystems are rivaled only
by lowland tropical rainforests (Cowling et al.
1996). The classic vegetation structures in mediterranean-type
ecosystems are evergreen shrublands dominated by species with sclerophyllous
leaves. These shrublands are termed maquis or garrigue in the Mediterranean
Basin, chaparral in California, matorral in Chile, fynbos in South Africa,
and kwongan or heathlands in southwestern Australia (Rundel
1998).
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Of the plant species growing in the Mediterranean-type ecosystems of the
world, 49% are aromatic (see table).
In analysing data on the worldwide distribution of genera of plants with
essential oils, Ross and Sombrero (1991)
conclude that Mediterranean-type ecosystems contain a disproportionate
share of essential oil producers: about 90 of the 153 plant genera
in 50 families across the globe accumulating volatile oils have a geographical
distribution in Mediterranean ecosystems.