01197nas a2200133   4500008004100000245004500041210004500086300001200131490000600143520078200149100001800931700002000949856009400969       1997                        eng d00aBiodiversity and environmental stability0 aBiodiversity and environmental stability  a315-3230 v63 aAlthough levels of biological diversity may seem to be equivalent in different areas, diversity is created and maintained by a range of different processes: overlap of habitat on gradients; a dynamic mosaic of communities; and accumulation and evolution of taxa in extremely stable areas. These different communities will respond in very different ways to disturbance. The most fragile are those whose component taxa are genetically adapted to the stability of a predictable environment. These areas are often under pressure from local rural populations and require intensive local conservation management actions. In other areas, where diversity is adapted to dynamism, communities are more resilient to disturbance and conservation can be best effected by policy instruments.1 aFjeldså, Jon1 aLovett, Jon, C.  ufile://localhost/Users/breda/Desktop/Literature/F/Fjeldsa%CC%8A%20&%20Lovett%201997-2.pdf02216nas a2200133   4500008004100000245014300041210006900184300001200253490000600265520167900271100001801950700002001968856009401988       1997                        eng d00aGeographical patterns of old and young species in African forest biota: The significance of specific montane areas as evolutionary centres0 aGeographical patterns of old and young species in African forest  a325-3460 v63 aA widely accepted paradigm for speciation in tropical forests, the refuge theory, requires periodic habitat fragmentation driven by global climatic fluctuations to provide conditions for allopatric speciation. This implies that comparative species richness in refugia is due to loss of diverse communities in areas affected by climatic cycles. In this study we compare distribution patterns of bird and plant taxa which we consider to be of either deep phylogenetic lineages or recent radiations. It is demonstrated that lowland areas which have been postulated as Pleistocene refugia are dominated by species which represent lineages of pre-Pleistocene age. Since variations in species richness within these forest tracts reflect currently apparent environmental variables which might be considered to determine carrying capacity, we do not need to postulate that richness is the result of changes in forest cover in the past. Recently diversified taxa of plants and birds are found mainly at the periphery of the main rain forest blocks and in habitat islands outside them. Here, peak concentrations of young restricted-range species are often congruent with clusters of old and biogeographically relictual species. It is suggested that this reflects special intrinsic environmental properties of these areas, in the form of long-term environmental stability caused mainly by persistent orographic rain or mist. In this case, richness is not necessarily due to extinction outside these areas. Stability not only enables survival of relictual taxa, but also promotes morphological differentiation of radiating taxa, leading to aggregates of taxa of restricted distribution.1 aFjeldså, Jon1 aLovett, Jon, C.  ufile://localhost/Users/breda/Desktop/Literature/F/Fjeldsa%CC%8A%20&%20Lovett%201997-1.pdf