PLANT DIVERSITY IN MEDITERRANEAN-CLIMATE REGIONS

The high plant diversity of mediterranean-climate regions has attracte d much attention over the past few years. This review discusses patter ns and determinants of local, differential and regional plant diversit y in all five regions. Local diversity shows great variation within an d between regions and explanations for these patterns invoke a wide ra nge of hypotheses. Patterns of regional diversity are the result of di fferential speciation and extinction rates during the Quaternary. Thes e rates have been influenced more by the incidence of fire and the sev erity of climate change than by environmental heterogeneity. All regio ns have a high number of rare and locally endemic taxa that survive as small populations, many of which are threatened by habitat transforma tion.