To many people, 'biodiversity' is almost synonymous with the word 'nature,' and 'nature' brings to mind steamy forests and the big creatures that dwell there. Fair enough. But biodiversity is much more than that, for it encompasses not only the diversity of species, but also the diversity within species... It is the diversity within species that keeps species going. This is the diversity upon which natural selection works, the diversity that fuels adaptation and evolution for everything from pandas to peas. Unless we appreciate the critical role that intra-species biodiversity plays in the survival of species, we risk seeing extinction as a numbers game, as something that happens when the last individual dies.
Cary Fowler in: Of Pandas and Peas: Saving the Diversity Within Species, The Huffington Post, 11 June 2010