Alpine plant biodiversity

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PLANTS AND LIFE PROCESSES

Endemism

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 the orophytes 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.

The two main types of endemic species
Paleoendemic species These species are often systematically isolated taxa, whose distribution areas represent the remnants of originally larger distribution ranges that have been reduced due to environmental changes. Check-out this phenomenon on the figure! The Ice Age, for example, led to the extinction of many species in the European Alps. However, several species could survive in non-glaciered areas at the south-western and the south-eastern end of the Alpine chain. Today, these two regions represent centres of paleoendemic species. Berardia subacaulis, for example, is one of them; it grows today as a relict of the Tertiary period in a part of the French Alps.	Neoendemic species These species result from the divergent adaptation to differing environmental conditions thereby leading to the formation of new species that are locally distributed. The evolution of neoendemic plant species is often triggered by polyploidy. The endemic species may have a higher ploidy level than its related taxa (apoendemics), or it may be diploid while its related taxa have a higher ploidy level (patroendemics). In cases where the endemic taxon and its related taxa are of equal ploidy level, the endemic species are called schizoendemics. Apo-, patro-, and schizoendemics are further subdivisions of neoendemics. Achillea erba-rotta s.str. and Achillea erba-rotta ssp. moschata are typical examples for neoendemics.
To explore the development of these two types of endemic species, click on the figures below.

29 August 2011 © ALPECOLe 2002-2007