Vegetation Structure in the Mediterranean Scrub Communities of California and Chile

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Abstract
The floristically distinct shrub communities of the Mediterranean climatic regions of S California [USA] and central Chile display similarities in vegetation structure. Similar trends in the representation of various features of growth-form and leaf morphology are found in the different parts of eqivalent elevation-aspect mosaics in the 2 areas. Quantitatively-determined growth-form types, comprised of groups of phenetically similar species, show strong similarities both in their composition and distributions through the 2 mosaics. In Mediterranean climatic regions with hot, dry summers similar environmental selection results in similar structural-functional systems. Despite these similarities, there are also some noticeable discrepancies between the 2 communities. The matorral vegetation of Chile possesses a significantly greater diversity, both of species and growth forms, than does the chaparral vegetation-type in California. This distinction, along with the more open nature of the vegetation at the lower elevation sites in Chile, can be attributed to a much more intensive land-use history in the matorral. An analysis of the influence of phylogeny of the evolution of aspects of morphology in the shrubs shows that, if phylogenetic constraints do exist, they can very frequently be overcome by environmental selection. Multivariate analysis is used to show, in respect of the characters considered, that a species is often more similar phenetically to a taxonomically unrelated species than it is to the other members of the same family or even genus.