The geographic distribution
of a taxon is limited.
Most taxa are confined to restricted regions, such as a single continent,
a part of a continent or even smaller regions. Taxa that occur in a relatively
small and more or less clearly delimited geographical area are called
endemics. Due to their geographical isolation, endemic species are extraordinarily
abundant on islands, such as Australia (95 % of the total flora are endemic),
Hawaiian Islands (83 %), Madagascar (80 %), Cuba (50 %) or the Canary
Islands (42 %). As a matter of fact, mountains represent islands of high
altitude in a sea of lowlands, and like islands, they are also relatively
rich in endemic species. In the European Alps, for example, about 400
vascular plant species are endemic, representing about 8 % of the total
number of vascular plant species (Pawlowski 1970). Considering solely
living exclusively in the subalpine and alpine zones, 31 % are endemic.
Some endemics are distributed throughout the whole chain of the Alps,
among them, for example, Gentiana bavarica. However, the distribution
areas of the majority of the endemic species are restricted to a smaller
part of the Alps, as with Sempervivum grandiflorum, occurring only
in the north-western Alps.