Biodiversity At The Periphery

Biodiversity has now become an integral element in environmental monitoring. Much attention has been given in recent years to the species-rich areas of the Earth, as there is an obvious concern that regions that contain so much of the world's evolutionary heritage do not become biologically impoverished. There is, however, a strong case for giving attention to marginal areas in the preservation of biodiversity even if the numbers of species that they contain cannot compare with the biological hotspots of the world.

Marginal areas, as has already been pointed out, are areas where climatic change is liable to cause disturbance either in location or the nature of the vegetation that survives in these potentially labile localities. Historically, they are areas that will have experienced climatic change in the past and therefore the species that live in these areas may be pre-adapted to climatic change and should therefore be considered particularly relevant in the study of species responses to fluctuating environments. It has been argued (Safriel et al., 1994) that peripheral populations have to be genetically more variable than those from core areas, since the variable conditions induce fluctuating selection, which maintains high genetic diversity. Alternatively, due to marginal ecological conditions at the periphery, populations there are small and isolated: the within-population diversity is low, but the between-population genetic diversity is high due to genetic drift. It is also likely that peripheral populations evolve resistance to extreme conditions. Thus, peripheral populations rather than core ones may be more resistant to environmental extremes and changes, such as global climate change induced by the anthropogenically emitted 'greenhouse gases'. They should therefore, it is argued, be treated as a bio-genetic resource used for rehabilitation and restoration of damaged ecosystems. Climatic transition zones are often characterized by a high incidence of species represented by peripheral populations and hybrids, and therefore should be conserved now as repositories of these resources, to be used in the future for mitigating undesirable effects of global climate change (Safriel et al., 1994).

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