Diversity, be it genetic, morphological, behavioural or ecological, is at the heart of many controversies. It fascinates us or worries us, depending on the context. But what is biological diversity? How useful is it, how is it generated and what are the foreseeable consequences of reducing it?
The incredible diversity of life
The life sciences have only recently begun to imagine the true extent of the diversity of life forms and the difficulty of quantifying it. Recent estimates of total eukaryotic diversity range from 1 to 5 × 107 species. Although only about ten thousand species of prokaryotes have been described, mainly because only a small number of bacteria can be grown in the laboratory, indirect molecular approaches (without culture) based on the analysis of DNA extracted from the environment suggest that there may be 109 or more prokaryotic species. However, even these already astronomical figures do not reflect the real diversity of life forms.
First, genotypic diversity within the same prokaryote species can be incredibly high. Members of one bacterial species share parts of their genome encoding essential metabolic and informational functions (called the core genomes), but often carry unique, strain-specific sequences for adaptation to local environmental pressures. In the case of the bacterium Escherichia coli, the core genome represents only 6% of the genes present in 61 sequenced strains. MORE